Tag Archives: quantum entanglement

a Representation of the quantum teleport of information from the surface of Earth to space--a sci-fi's fan's dream, almost. ((IMAGE BY CAS))

Quantum Teleportation: Separating Science Fact from Science Fiction

It goes without saying that many terms and concepts from science, and particularly physics, find themselves transported from the pages of journals and reports to the comic book page or TV screen — albeit intrinsically changed. Quantum teleportation is an interesting example of this process working in reverse. 

A recreation of the transporter room from the Enterprise D as featured in the show Star Trek: The Next Generation. Unfortunately, teleportation as made famous by the Star Trek franchise is impossible, but quantum teleportation is no less fascinating. (Konrad Summers/ CC by SA 2.0)

Though physicist and information theorist Charles Bennet took the term ‘teleportation’ from popular culture, quantum teleportation is radically different than the process used by the crew of the Enterprise to ‘beam down’ to an alien vista. But despite this; that image of Kirk, Spock, Bones, and a crew of hapless red shirts travelling down to the surface of a planet and back — albeit minus several of the red shirts — is so ubiquitous it’s hard for even professional physicists to escape.

“Of course, I think of Star Trek where people and things are being ‘beamed-up’,” Ulf Leonhardt from the Department of Physics of Complex Systems at the Weizmann Institute of Science tells me when I ask him what the word ‘teleportation’ means to him. And Leonhardt is no stranger to quantum teleportation either. He is renowned for his work in quantum optics — one the fields in which quantum teleportation is explored, in fact, its no exaggeration to say ‘he wrote the book on it.’

This ubiquity of the pop-culture interpretation of teleportation is a special kind of hindrance when it comes to the understanding of quantum teleportation as the two concepts are so radically different. 

The first, and most radical difference, you won’t be using quantum teleportation to beam to the surface of an alien world or down to the local shops anytime soon. This isn’t because quantum teleportation isn’t up and running; we’ve had the technology in operation since the mid-nineties. It’s because quantum teleportation has nothing to do with the transport of matter.

Mind over Matter–How Quantum Teleportation Shifts Information

The idea of being able to instantly — or almost instantly — relocate matter from one location to another, was granted the name ‘teleportation’ by a purveyor of the weird Charles Fort in his 1931 book ‘Lo!’. But despite this; the idea existed sometime before this.

Many early examples of teleportation were, unsurprisingly, described as being magical in nature, but with the advent of the industrial revolution, remarkable tales of intrigue and suspense began to move away from supernatural explanations to ones of science–albeit none more credible in nature. The first example of matter being transported instantaneously from one location to another being performed ‘scientifically’ occurred in an 1897 novel.

In Fred T. Jane’s ‘To Venus in Five Seconds: An Account of the Strange Disappearance of Thomas Plummer, Pillmaker,’ the titular hero is transported from a pleasant summer house — albeit filled with strange machinery — to the planet Venus where he encounters warring locals and some other displaced Brits. This is the first recorded example of scientific equipment used to transport a hero to the surface of an alien world in fiction, a function which will, of course, become the most infamous use for teleportation.

An illustration from ‘To Venus in Five Seconds: An Account of the Strange Disappearance of Thomas Plummer, Pillmaker,’ by Fred T Jane. Thanks to a teleportation mishap Plummer is menaced by the rather un-PC inhabitants of Venus (A.D. Innes, 1897, the University of Wisconsin – Madison)

But quantum teleportation doesn’t concern the transport of matter — instantly or otherwise — rather it’s about the transmission of information.

“I think for a layman teleportation means instantaneous transport of matter, but a physicist knows that this is impossible,” Leonhardt explains. “Rather, teleportation is the transport of the information of how to assemble matter to make up an object.

“There is zero chance for the instantaneous transport of matter, but a good chance for the transfer of quantum information of not-too-complex systems. Teleporting people is out of the question, though.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

So if you’re not going to be taking a trip in a teleporter any time soon. With that said, we can investigate the nature of the information that can be sent via quantum teleportation.

From Here to There: State to State Communication

As quantum teleportation doesn’t concern the transmission of matter, but information, it’s more correct to regard it as a form of communication rather than one of transport like its sci-fi counterpart. But that leaves the question, what is being communicated?

“Quantum teleportation is the transport of a quantum state from one object to another,” Leonhardt says. “The quantum state contains all the possible information about the object.”

Thus, quantum teleportation really means transferring the quantum structure of an object from one place to another without the movement of that physical object. This ‘quantum structure’ refers to qualities that a system or a particle can possess, things like momentum, polarization and spin. 

The quantum mechanical counterpart of classical bits can be encoded with a wealth of information (Nicholas Shan)

This information is encoded in qubits — the quantum-mechanical analogue of classical bits. Whereas a bit can only hold the information ‘true’ or ‘false’ a qubit can be encoded with a deep wealth of information. So, quantum teleportation is a mechanism of moving this qubit without moving the particle with which it is associated. This communication requires the system at the starting point and the system representing the endpoint are entangled. 

“The quantum state cannot be measured for an individual system, because an observation may ruin it,” Leonhardt explains.

“Entanglement between the two ports of the quantum teleportation system is an essential ingredient.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

The first experiments with quantum teleportation dealt with the transfer of state information between single entangled photons, but it has since been realised in a variety of quantum systems — electrons, ions, atoms and even superconducting circuits. 

What is important to note though, is that quantum teleportation isn’t simply creating two copies of the same quantum system. In fact, that is something expressly forbidden by the rules of quantum physics. 

No Cloning Around!

Christopher Nolan’s magical 2006 thriller The Prestige–based upon a 1995 novel by Christopher Priest– focuses on the intensifying rivalry of magicians Robert Angier (Hugh Jackman) and Alfred Borden (Christian Bale). The feud consumes both men costing the lives of both their loved ones and ultimately themselves. 

During the course of this self-destruction, in an attempt to out-do Borden’s most spectacular illusion, Angier seeks the help of a fictionalised version of Nikola Tesla. Telsa provides Angier with a teleportation device but warns him of the machine’s terrible cost. 

The inimitable David Bowie as Nikola Tesla in Christopher Nolan’s The Prestige. In the film, Tesla warns an illusionist with a grudge the terrible cost of his teleporter but is not heeded. (Warner Bros. Pictures 2006)

That cost is that every time the machine is used, it creates a copy of Angier. A clone. Meaning that the illusionist must murder the ‘original him’ each time the trick is performed. He dispatches ‘himself’ in a tank of water hidden beneath the stage where the teleport pod sits. A fitting way for a magician to go.

But, on the quantum scale, there are specific rules in place to prevent the cloning of a system every time an act of quantum prestidigitation is performed. Quantum teleportation has a strict ‘no cloning’ rule. “The no-cloning theorem states that one cannot create two identical copies from the same individual quantum system,” Leonhardt states.

“The quantum state is too fragile and would be compromised in such a process.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

The Heisenberg uncertainty principle is just one of the rules of quantum physics that the successful cloning of a system would jeopardise. The most well-known version of the uncertainty principle, for example, states that it is impossible to precisely measure the momentum and the position of a quantum system. The more precisely one knows one, the less precisely one can know the other. 

But, if quantum teleportation allowed a system to be cloned, then an enterprising researcher could measure the position of the original system and simultaneously measure the momentum of the ‘clone’, thus violating this rule.

In fact, all sorts of messiness would ensue with a system that could be cloned, including, eventually, the possible violation of causality itself. 

That means that quantum teleportation really ‘moves’ the quantum state from one location to another, destroying that state in the original port… Possibly by drowning it in a tank. 

Quantum Teleportation… Not Instantaneous, But ASAP

Despite the fact teleportation mishaps often became the focus of episodes of Star Trek, initially, it was little more than a Deux ex Machina that allowed the story to flow without characters being tied up by long shuttle journeys. In order for the narrative of a concise 42-minute episode of TV to flow in a pleasing way, it was necessary for characters to be able to instantly move from place to place.

Unfortunately, quantum teleportation differs from its pop-culture ancestor in this respect too. 

Quantum Teleportation. Words and Graphic Innebrooks research team
Quantum Teleportation. Words and Graphic Innebrooks research team

Though instant transmission of information in quantum physics does exist in the form of the instant change in an entangled system when a measurement is made on one part of that system. That measurement and the adoption of a state that it causes results in the partner system adopting the corresponding state instantly — even if it is at the opposite side of the Universe.

This apparent violation of the universal speed limit of the speed of light in a vacuum troubled Einstein so much he referred to it as ‘spooky action at a distance’ and suggested that it demonstrated quantum physics was an incomplete theory with hidden variables yet to be discovered. But, this aspect of quantum physics has been confirmed by decades of research after the Austrian physicist’s death.

Quantum physics is complete, information does travel between entangled quantum systems or particles instantaneously. Yet despite the fact that quantum teleportation functions on the basis of entanglement — passing a state between two entangled particles — that doesn’t mean that quantum teleportation can transfer information instantly too. 

That’s because quantum teleportation isn’t entirely quantum.

When a qubit is transmitted from a sender to a receiver — we’ll call them Alice and Bob respectively as has become standard when describing quantum communication — it’s necessary to transmit two bits of classical information per qubit from Alice to Bob.

This means a classical communication channel has to be created so that Alice and Bob can communicate the results of their measurements. If this isn’t done, Alice and Bob have no way to reconstruct the initial state and the reconstruction will be random. 

Thus, the downside of this is that it limits the speed of information transfer to the speed of classic communication. A qubit can’t be reconstructed before the classical information is received. Researchers can use lasers and photons as the basis of this classical communication system, so even though there is a speed limit, it’s the fastest speed achievable. This also means it can be achieved through ‘open space’ without the need for fiber optic cables. 

Or course, that means not only can Kirk not instantly return to the Enterprise, but he can’t even get a ‘beam me up’ command sent instantly.  

Quantum Teleportation in Practice

The most likely use of quantum teleportation is in the development of quantum computing, quantum networks, and eventually, a quantum internet. Currently, academic debate over this quantum future is focused on which quantum teleportation system is most reliable. 

This image shows crystals which contain photonic information after quantum teleportation. (© GAP, University of Geneva (UNIGE))
This image shows crystals which contain photonic information after quantum teleportation. (© GAP, University of Geneva (UNIGE))

In 2015 paper published in Nature Photonics scientists from the Freie Universität Berlin and the Universities of Tokyo and Toronto, performed a comprehensive review of theory and experiment surrounding quantum teleportation, concluding that no technology in isolation yet provides the perfect solution, meaning hybridisation is needed if quantum computing is ever to be a reality.

This means that many physicists are currently working on improving the distances over which quantum teleportation can be achieved and the kind of quantum systems that states can be communicated between. 

An example of this is the fascinating work of Nicholas Gisin at the University of Geneva (UNIGE). Gisin and his team have consistently been at the cutting edge of pushing the distances across which quantum teleportation can be achieved. In a 2014 study, Gisin’s UNIGE team not only pushed the distance across which a state could be teleported — over 25 meters through an optical cable — but they also managed to communicate the state from a photon to a solid crystal, showing that states can be passed between radically divergent systems. 

Gisin’s research is constantly being improved upon thus the distance across which a quantum state can be transmitted is stretching. And this includes maybe finally reaching the ‘final frontier.’

Space: Probably Not The Final Frontier for Quantum Teleportation

In July this year, scientists finally made teleportation to space a reality , maybe offering some compensation to disappointed sci-fi fans.

a Representation of the quantum teleport of information from the surface of Earth to space--a sci-fi's fan's dream, almost. ((IMAGE BY CAS))
Representation of the quantum teleport of information from the surface of Earth to space–a sci-fi’s fan’s dream, almost. ((IMAGE BY CAS))

In a series of experiments, described by a paper published in the journal Science an international team of researchers described the communication of a quantum state into space and across a distance of up to 870 miles to the Chinese quantum-enabled satellite Micius. The research represented the first meaningful quantum optical experiment to test the fundamental physics existing between quantum theory and gravity. 

Soon, a new Chinese satellite will orbit Earth a distance up to sixty times greater than that between Micius–launched in 2016– and the planet’s surface. This will allow researchers to push the boundaries of quantum teleportation even further.


Ulf Leonhardt believes, however, that our understanding of quantum teleportation and our concept of what is achievable within will eventually become as outmoded as the science described in the escapades of Thomas Plummer.

“I like science fiction as scenarios of social thought experiments, but not so much for technological dreams,” Leonhardt says. “It is amusing to browse through Victorian science fiction. They projected their world of steel and steam into the future, which clearly shows the limits of technological imagination.”

 “Our modern projections will share the same fate.”

Ulf Leonhardt, author of ‘Essential Quantum Optics’

Sources and Further Reading

Leonhardt. L, ‘Essential Quantum Optics,’ Cambridge University Press, [2010].

Bussières. F, Clausen. C, Gisin. N, et al, ‘Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory,’ Nature Photonics, [2014]

Pirandola. S, Eisert. J, Weedbrook. C, et al, ‘Advances in quantum teleportation,’ Nature Photonics, [2015]

The Micius satellite--the first experiment to test quantum physics in space

Quantum satellite investigates the gap between Quantum Mechanics and General Relativity

Experimental diagram of testing gravity-induced decoherence of entanglement (provided by University of Science and Technology of China)

Quantum mechanics and general relativity represent the two most successful theories in 20th-century physics. But despite almost 100 years of continued experimental verification and practical application, researchers remain unable to unite the disciplines. 

As general relativity describes the effects of gravity on Einstein’s four-dimensional spacetime — three dimensions of space and time — this means that a quantum theory of gravity continues to evade detection. 

As the problem of unification remains unsolved, physicists put forward various models that require experimental verification. 

A team of international researchers has developed a framework to test a model which may account for the breakdown of general relativity’s rules on the quantum scale. They tested this framework using the quantum satellite — Micius — a Chinese project which tests quantum phenomena in space. 

The research — documented in a paper published in the journal Science — represents the first meaningful quantum optical experiment testing fundamental physics between quantum theory an gravity, says Jian-Wei Pan, director of the CAS centre for Excellence in Quantum Information and Quantum Physics at the University of Science and Technology of China.

Pan and his team wanted to test the event formalism model of quantum fields model — a theory that suggests that the correlation between entangled particles would collapse — a phenomenon known as decoherence — as they pass through the gravitational well of Earth. The idea is that the differences in the gravitational force would force decoherence as the particle experiencing less gravity would be able to travel with less constraint than its counterpart in an area of stronger gravity.

Pan suggests that event formalism presents a description of quantum fields existing in spacetime as described by general relativity — consisting of curvature caused by the presence of mass. Thus if the team can observe this model’s effects, they can imply the presence of quantum phenomena on a larger scale as described by general relativity.

Pan says: “If we did observe the deviation, it would mean that event formalism is correct, and we must substantially revise our understanding of the interplay between quantum theory and gravity theory.”

In their test, the team used pairs of particles described as ‘time-energy entangled’ — a recently discovered type of entanglement which photons are entangled in terms of their energies and the times they are detected. 

The team was unable to detect the particles deviating from standard behaviour expected in quantum mechanics, but they plan to retest a version of their theory that is more flexible. 

“We ruled out the strong version of event formalism, but there are other versions to test,” Pan says. “A modified model remains an open question.”

To put this revised version to the test a new satellite will be launched that will orbit up to sixty-times higher than Micius — enabling it to test a wider variation in gravitational field strength. 

Original research: https://science.sciencemag.org/content/early/2019/09/18/science.aay5820

Purdue researchers have modified a popular theorem for identifying quantum entanglement and applied it to chemical reactions. This quantum simulation of a chemical reaction yielding deuterium hydride validated the new method. ( Purdue University image/Junxu Li)

Physicists measure quantum entanglement in chemical reactions

Quantum entanglement and other quantum phenomena have long been suspected by scientists to play a role in chemical reactions like photosynthesis. But, until now, their presence has been hard to identify.

Purdue researchers have modified a popular theorem for identifying quantum entanglement and applied it to chemical reactions. This quantum simulation of a chemical reaction yielding deuterium hydride validated the new method. ( Purdue University image/Junxu Li)

Purdue researchers have modified a popular theorem for identifying quantum entanglement and applied it to chemical reactions. This quantum simulation of a chemical reaction yielding deuterium hydride validated the new method. ( Purdue University image/Junxu Li)

Researchers at Purdue University have unveiled a new method that enables them to measure entanglement — the correlation between the properties of two separated particles — in chemical reactions.

Discovering just what role entanglement play in chemical reactions has implications for the improvement of technologies like solar energy systems if we can learn to replicate them.

The study — published in the journal Science Advances — takes the theorem ‘Bell’s Inequality’ and generalises it to identify entanglement in chemical reactions. In addition to theoretical arguments, they also performed a series of quantum simulations to verify this generalized inequality.

Sabre Kais, a professor of chemistry at Purdue, explains further: “No one has experimentally shown entanglement in chemical reactions yet because we haven’t had a way to measure it. For the first time, we have a practical way to measure it.

“The question now is, can we use entanglement to our advantage to predict and control the outcome of chemical reactions?”

Bell’s Inequality — identifying entanglement.

John S. Bell designed an experiment to prove if quantum mechanics is complete (CERN)

John S. Bell designed an experiment to prove if quantum mechanics is complete (CERN)

Since its development in 1964, Bell’s Inequality has been validated as the go-to test that physicists use to identify entanglement in particles. The theorem uses discrete measurements of properties of particles such as the orientation in their spin — nothing to do with angular momentum in the quantum world — to find if the particles are correlated.

The problem is, discovering entanglement in chemical reactions requires that measurements are continuous. This means measuring aspects such as the angles of beams which scatter reactants forcing them into contact and transform into products.

To combat this, Kai’s team generalised Bell’s Inequality to include continuous measurements in chemical reactions, in a similar way to how the theorem had previously been generalised to examine light — photonic systems.

The team then tested their generalised Bell’s inequality using a quantum simulation of a chemical reaction yielding the molecule deuterium hydride.

The process was built on a foundation established in a 2018 experiment developed by Stanford University researchers that aimed to study the quantum states of molecular interactions.

Because the simulations validated the Bells’s theorem and showed that entanglement can be classified in chemical reactions, Kais’ team proposes to further test the method on deuterium hydride in an experiment.

Kais says: “We don’t yet know what outputs we can control by taking advantage of entanglement in a chemical reaction — just that these outputs will be different.

 “Making entanglement measurable in these systems is an important first step.”

This is what quantum entanglement looks like

Scientists have managed to take a photo of one of the most bizarre phenomena in nature: quantum entanglement.

Image credits: University of Glasgow.

There’s a reason why Einstein called quantum entanglement ‘spooky action at a distance’. Quantum entanglement, by everything that we know from our macroscopic lives, should not exist. However, the laws of quantum mechanics often defy what seems normal to us, and this bizarre phenomenon actually underpins the whole field of quantum mechanics.

Quantum entanglement occurs when a pair or a group of particles interact with each other and remain connected, instantaneously sharing quantum states — no matter how great the distance that separates them (hence the spooky action at a distance). This connection is so strong that the quantum state of each particle cannot be described independently of the state of the other(s).

Predicting, achieving, and describing this phenomenon was a gargantuan task that took decades. Photographing it is also a remarkable achievement.

Researchers from the University of Glasgow modified a camera to capture 40,000 frames per second. They operated an experimental setup at -30 degrees Celsius (-22 F) in pitch-black darkness. The experimental setup shoots off streams of photons entangled in a so-called Bell state — this is the simplest example of quantum entanglement.

The entangled photons were split up, with one of them passing through a liquid crystal material called β-barium borate, triggering four phase transitions. These four phase transitions were observed in the other, entangled photons.

A composite of multiple images of the photons as they go through the quantum transitions. Image credits: University of Glasgow.

Einstein staunchly believed that quantum mechanics does not tell the whole story and must have another, underlying physical framework. He even developed a series of experiments meant to disprove this quantum mechanics — which, ironically, ended up confirming the foundations of quantum mechanics.

However, people often forget that Einstein can also be regarded as one of the fathers of quantum mechanics. For instance, he described light as quanta in his theory of the Photoelectric Effect, for which he won the 1921 Nobel Prize. Niels Bohr and Max Planck are often regarded as the two founders of quantum mechanics, although numerous outstanding physicists worked on it over the years. For instance, physicist John Stewart Bell helped define quantum entanglement, establishing a test known as ‘Bell inequality’. Essentially, if you can break Bell inequality, you can confirm true quantum entanglement — which is what researchers have done here.

“Here, we report an experiment demonstrating the violation of a Bell inequality within observed images,” the study reads.

Lead author Dr. Paul-Antoine Moreau of the University of Glasgow’s School of Physics and Astronomy comments:

“The image we’ve managed to capture is an elegant demonstration of a fundamental property of nature, seen for the very first time in the form of an image.”

“It’s an exciting result which could be used to advance the emerging field of quantum computing and lead to new types of imaging.”

The study was published in Science Advances.


China breaks quantum entanglement record at 18 qubits

Physicists in China just broke a new record by achieving quantum entanglement with 18 qubits, surpassing the previous record of 10. This significant breakthrough puts us one big step closer to realizing large-scale quantum computing.


Credit: Youtube screenshot.

It’s hard to find a stranger, more exotic phenomenon than quantum entanglement — the idea that two entangled particles, or qubits, can influence each other’s state instantly even when they’re light-years apart.

Even if you separate entangled particles by billions of miles, changing one particle will induce a change in the other. This information appears to be transmitted instantaneously, with no violation of the classical speed of light because there’s no “movement” through space.

When Albert Einstein first spoke about quantum entanglement in 1935, he famously called it “spooky action at a distance.” But although quantum entanglement is still very strange, at least scientists are no longer strangers to it. Physicists have so far shown how quantum entanglement works over various distances both on land and in space. Most recently, a Chinese satellite entangled particles over 1,200 km apart, paving the way for the future’s quantum communication and quantum encryption networks.

Maintaining quantum entanglement is an extremely delicate matter, however, as even the slightest perturbance can induce decoherence — the destruction fo the quantum states.

In a new record, Pan Jianwei and colleagues at the University of Science and Technology of China, eastern China’s Anhui Province, demonstrated a stable 18-qubit state. The previous record of 10 qubits was set by the same team. The breakthrough was made possible by simultaneously manipulating the freedom-paths, polarization, and orbital angular momentum of six photons.

“The speed of quantum computing grows exponentially as the number of qubits in an entangled state increases … the achievement of an 18-qubit entanglement this time has set the world record for largest entanglement state in all physical systems,” Wang Xilin, a member of Pan’s team told Global Times.

“With that goal, the team’s next step will be to realize a 50-qubit entanglement and manipulation,” he added.

Full control over the number of entangled particles is fundamental to quantum information processing that enables quantum computers to do their magic.

In normal silicon computer chips embedded into your laptop or smartphone, information is rendered in one of two states: 0 or 1. In a quantum computer, information can also be stored and relayed in both states at once, holding exponentially more information. As an analogy, imagine being able to read a whole library at once rather than one book at a time.

By one estimate, a quantum computer with 50 quantum bits would be more powerful in solving quantum sampling problems than today’s fastest supercomputer. Quantum computers are able to crunch through big data problems that involve finding optimum solutions from vast numbers of options, which is extremely important for a number of medical fields (i.e. protein folding, gene sequencing) and climate research. One of the biggest selling points of quantum computers, however, is security. A hacker can make a copy of your email now without you ever knowing; a hack of a quantum system, however, is bound by the laws of physics to leave traces.

So, how long before quantum computers become a reality? Efforts such as those of Jinwei and colleagues demonstrate that we’re coming closer to shifting the paradigm in computing — and they are not alone. According to McKinsey & Company, in 2015, there were about 7,000 researchers worldwide working in the field, with about US$1.5 billion a year being spent. Today, there are certainly more resources invested into quantum computing research as governments and corporations chase the advantages of quantum technology.

Credit: Max Pexels.

Mindbending ‘Spooky Action at a Distance’ experiment involving 100,000 gamers proves Einstein wrong

Credit: Max Pexels.

Credit: Max Pexels.

It’s hard to find a stranger, more exotic phenomenon in physics than quantum entanglement — the idea that two entangled particles can influence each other’s state instantly even when they’re light-years apart. The whole idea is so baffling that Einstein famously referred to it as ‘spooky action at a distance.’

The physicist had a lot of qualms with quantum entanglement, such as the fact that it contradicts so-called  “local realism” — the idea that things have properties whether or not you observe them. Now, the most sophisticated experiment of its kind to date has confirmed quantum entanglement, proving Einstein wrong.

The randomness of humanity

The huge international collaboration involved more than 12 teams of researchers in 10 countries as well as 100,000 volunteer gamers. Scientists called the experiment the Big Bell Test — a Bell test is an experiment designed to test the validity of quantum entanglement.

Such tests were first introduced during the 1960s by the Irish physicist John Bell who proposed testing quantum entanglement by comparing randomly chosen measurements, like the polarization of two entangled particles that exist in different locations. If the number of times that the state measurements of the two particles mirror each other goes above a certain threshold, this suggests the separated particles enter their state only at the moment they are measured. The immediate consequence is that the particles can communicate instantly with each other. Spooky, indeed!

At the same time, this behavior contradicts the principle of local realism (upon which classical physics is based) –– the idea that phenomena and objects function irrespective of whether someone’s watching or not.

The problem with Bell tests, however, is that what you choose to measure has to be truly random. Even a computer random generator isn’t truly random, which is why scientists had to think outside of the box to design this experiment. Humans are pretty random and when they collectively number in the thousands, we humans can be unpredictable enough to fulfill the strict criteria for a Bell test.

The physicists recruited a staggering 100,000 people who were invited to play a smartphone game called the Big Bell Quest. Each player had to press two buttons on a screen, with respective values of one and zero. All of these random choices were used by different labs across five continents to select measurement settings for comparing entangled particles. Each lab performed a different experiment using different particles. For instance, single atoms, groups of atoms, photons, and so on.

When all the results were aggregated and compared, they suggested that local realism is not universally valid, confirming spooky action at a distance.

“We showed that Einstein’s worldview of local realism, in which things have properties whether or not you observe them, and no influence travels faster than light, cannot be true — at least one of those things must be false,” Morgan Mitchell, a professor of quantum optics at the Institute of Photonic Sciences in Barcelona told Live Science.

There are two possible explanations of these findings: either our observations actually change the state of the observed or particles are communicating with each other through some unbeknownst means that is yet invisible to us.

“What is most amazing for me is that the argument between Einstein and Niels Bohr, after more than 90 years of effort to make it rigorous and experimentally testable, still retains a human and philosophical element. We know that the Higgs boson and gravitational waves exist thanks to amazing machines, physical systems built to test the laws of physics. But local realism is a question we can’t fully answer with a machine. It seems we ourselves must be part of the experiment, to keep the Universe honest,” Mitchell said in a statement. 

All of this is quite a lot to swallow in one go but, at the end of the day, it’s impressive how far science has come and how much we can learn about the universe if we collaborate. Imagine what one million or one billion minds would be able to achieve when they put their minds to it.

“I also particularly enjoyed the outreach and public involvement side,” said Geoff Pryde from Griffith University in Australia.

“I enjoyed that we gave people an opportunity to do something which influenced how the experiment ran.”

Scientific reference: Challenging local realism with human choices, The Big Bell Test Collaboration, Nature 2018. 

Illustration of the 15-micrometre-wide drumheads prepared on silicon chips used in the experiment. The drumheads vibrate at a high ultrasound frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Credit: Aalto University.

Scientists demonstrate quantum entanglement with objects big enough to see

Illustration of the 15-micrometre-wide drumheads prepared on silicon chips used in the experiment. The drumheads vibrate at a high ultrasound frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Credit: Aalto University.

Illustration of the 15-micrometer-wide drumheads prepared on silicon chips used in the experiment. The drumheads vibrate at a high ultrasonic frequency, and the peculiar quantum state predicted by Einstein was created from the vibrations. Credit: Aalto University.

Physics deals with its fair share of strangeness and — let’s be honest here — that’s especially abundant in quantum theory. However, you’ll be challenged to find a weirder, more counter-intuitive concept than quantum entanglement, the phenomenon in which the quantum states of two or more objects are intertwined such that they have to be described with reference to each other, even though the individual objects may be spatially separated.

Even if you separate entangled particles by billions of miles, changing one particle will induce a change in the other. This information appears to be transmitted instantaneously, with no violation of the classical speed of light because there’s no “movement” through space.

When Albert Einstein first spoke about quantum entanglement in 1935, he famously called it “spooky action at a distance.” But although quantum entanglement is still very strange, at least scientists are no longer strangers to it. Physicists have so far shown how quantum entanglement works over various distances both on land and in space. Most recently, a Chinese satellite entangled particles over 1,200 km apart, paving the way for the future’s quantum communication and quantum encryption networks.

The problem with entanglement is that it’s very fragile, as the conditions necessary to maintain the quantum state can be challenging. What’s more, entanglement has only been demonstrated in microscopic systems such as light or atoms — that’s, until recently, when an international team of researchers showed how to generate and detect entanglement of macroscopic objects.

The researchers led by Prof. Mika Sillanpää at Aalto University in Finland entangled two individual vibrating drumheads made from metallic aluminum. Each drumhead had a diameter the size of a human hair, making it huge by quantum standards.

“The biggest challenge was the theoretical understanding of the data. We measured the data exactly two years ago, but it is published not until now! This is because it was so demanding to develop the proper theoretical model. When we took the data, we had no idea if we are entangled or not. It was a great moment later to find out that all features of the data were explained by the new modeling,” Sillanpää told ZME Science.

In order to entangle the two bodies, the researchers forced them to interact via a superconductive microwave circuit, whose magnetic fields absorb all the thermal disturbances thus removing noise — and leave behind only the quantum mechanical vibrations. It’s with these high ultrasonic vibrations that the scientists entangled the drumheads. All of this occurred at a temperature near absolute zero, -273 °C, where molecular motion almost grinds to a halt.

Quantum entanglement between the large bodies was maintained for up to half an hour. When asked if there is any limit to how large any two objects can be for them to become entangled, Sillanpää said that there are no fundamental limits but, practically, gravity might “collapse” the quantum properties of objects that are too large.

“How large, is totally unclear. There are, however, limits that in practice are fundamental: Let us consider for example, a cat-size object that is in a quantum state of being at the same time in two places that are spaced by centimeters. Now, the neutrino irradiation (which is impossible to avoid because even the Earth is transparent to neutrinos) from the Sun will destroy such a quantum state in about a pico-second (one millionth of a micro-second), so such states do not appear in nature.”

This exciting research will prove very important in the forthcoming quantum technology revolution. The results show that it is possible to generate and stabilize exotic quantum states in large mechanical objects, enabling all sorts of new opportunities like novel quantum technologies and sensors that might revolutionize research in fundamental physics. Perhaps research in the future attempting to teleport mechanical vibrations might offer some very interesting surprises.

“To build a quantum internet that will connect distant quantum computers, one needs entangled particles or objects. The vibrating drumheads can serve as such components that convert the quantum bits in a processor into the flying quantum information. In fundamental research, one could improve the sensitivity of the existing gravitational wave detection systems,” Sillanpää explained.

“Nature can be more awesome than you could ever imagine!” the physicist concluded.

The findings appeared in the journal Nature.

Micius satellite as it passes over China and Austria. Credit: Chinese Academy of Sciences.

Scientists make first quantum video call. It’s supposedly unhackable

Chinese researchers made the first quantum secure video using subatomic particles called photons. The call was made between the Chinese Academy of Sciences and the Austrian Academy of Sciences, demonstrating the practicality of quantum key distribution — a feat that will likely radically change the way sensitive data is shared from now on.

Micius satellite as it passes over China and Austria. Credit: Chinese Academy of Sciences.

Micius satellite as it passes over China and Austria. Credit: Chinese Academy of Sciences.

This was the climax of more than ten years of research on behalf of Chinese scientists. Earlier last year, the nation launched ‘Micius’, the first quantum satellite, into Earth’s orbit. This summer, the satellite beamed entangled particles of photons to three ground stations across China, each separated by more than 1,200km. This marked a 10-fold increase in the distance under which entanglement was maintained compared to the previous record.

 “The exchange of quantum encrypted information over inter-continental distances confirms the potential of quantum communication technologies as opened up by fundamental research”, says Anton Zeilinger, a quantum physicist at the University of Vienna. He is convinced: “This is a very important step towards a world-wide and secure quantum internet.”

The most secure means of encryption — for the time being

Quantum entanglement — or what Einstein used to call “spooky action at a distance” — is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others. If one of two entangled particles changes its quantum state, it influences the other and directs an instant change, even if the two particles are spaced apart at the other ends of the universe. At least, that’s what our current understanding is. Giving one particle an ”up” spin, for instance, always means its entangled partner has a ”down” spin. This change is instantaneous, according to physicists.

In a demonstration that took place on Friday, the team from the Chinese Academy of Sciences led by physicist Jian-Wei Pan generated a secure key from Micius. The satellite is able to fire single photons suspended in superposition that can be used to generate a random sequence of bits. It’s this string of bits that’s the secret code that two parties use to either encrypt or decrypt a message through a method called the one-time pad. 

During the team, the Chinese researchers connected a ground station in Xinglong and the Micius satellite as it passed overhead, orbiting about 500 kilometers above Earth. From the Chinese site, the secure key was sent through fiber optics to Beijing, where the Chinese Academy of Sciences is located. When Micius passed above Vienna, the satellite sent the key to collaborators at the Austria Academy of Sciences. With this key at hand, the two groups initiated a video conference through a standard VPN protocol. The call lasted for about half an hour and the quality was reportedly ‘excellent’.

For many years, scientists have investigated the theoretical aspects of quantum encryption. Now, after investing considerable resources (launching a satellite and building three dedicated facilities), China proves it can be done.

What makes this type of communication extremely secure is that any evesdropping will change the quantum state and thus scramble the message.

“If somebody attempts to intercept the photons exchanged between the satellite and the ground station and to measure their polarization, the quantum state of the photons will be changed by this measurement attempt, immediately exposing the hackers,” said Johannes Handsteiner from the Austrian Academy of Sciences in a statement. 

For now, bandwidth is fairly limited, so we’re not going to see a lot of people switch to quantum encryption just yet. The key was transmitted at a rate of 200 kilobytes per orbit between Micius and the Xinglong station, and 50 kB per orbit between the satellite and the Vienna ground station, IEEE Spectrum reported.

Next, China plans on further demonstrating quantum encryption with partners from Italy, Germany, Russia, and Singapore.

Chinese satellite beams entangled particles over 1,200km away, sets the stage for unhackable quantum network

Quantum satellites communicate by speaking with ground based stations, as information is beamed between the two locations. Fast feed-forward is needed for the ground station to keep track of the satellite, ensuring that the information isn’t lost in space. Image courtesy of 中科大 (University of Science and Technology of China).

Using a satellite orbiting 300 miles above the planet, Chinese researchers beamed entangled particles of photons to three ground stations across China, each separated by more than 1,200km. The achievement marks a 10-fold increase in the distance over which entanglement has been maintained. Previously, scattering and coherence decay limited the link separations to only 100km. As such, this successful run is cementing China’s positioning as the leader of the burgeoning field of quantum communication and quantum encryption. The latter might eventually lead to the formation of an allegedly unhackable ‘quantum internet’ with important consequences to society and of immense geopolitical value for those government controlling it.

The beginning of a global quantum network

Quantum entanglement — or what Einstein used to call “spooky action at a distance” — is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently of the others. If one of two entangled particles changes its quantum state, it influences the other and directs an instant change no matter if the two particles are spaced apart at the other ends of the universe. Giving one particle an ”up” spin, for instance, might always mean its entangled partner has a ”down” spin. This change is instantaneous.

This phenomenon isn’t some weird, purely theoretical physics caveat that exists solely in the minds of awkward theoretical physicists. It’s quite practical, even. Using the power of entanglement scientists at the National Institute of Standards and Technology (NIST) instantly transferred information from on proton to another one 100 kilometers away in 2015. Physicists call this “quantum teleportation”.

To use entangled photons to communicate, ground-based systems use fiber optic cables or relay the particles through the open air. However, this introduces the risk of collision with ordinary particles disrupting the delicate quantum states of our entangled photons. The longer the particles have to travel, the greater the risk of decoherence, which is why transmission distances were limited to a few hundred kilometers.

An alternative would be to use so-called ‘quantum memory’ modules, linked and spread out in a daisy-chain. But in order to do all that, you have to know you’ve stored the photons without actually measuring them.This is theoretically possible but the technology is too out of reach to be of any practical use in the near future.

It remains that the only current viable option for a global communications network is to beam quantum keys through the vacuum of space then distribute them across tens to hundreds of kilometers using ground-based nodes. This is where China’s 600-kilogram “Micius” satellite comes in.

Press illustration of Micius.

Press illustration of Micius.

Micius is the world’s first quantum satellite. Launched in 2016, the satellite named after a famous Chinese philosopher employs a crystal that produces entangled pairs of photons. To communicate, the satellite aligned itself with ground stations in the cities of Delingha and Ürümqi—both on the Tibetan Plateau—as well as in the city of Lijiang in China’s far southwest, and fired entangled particles in pairs to generate a secret key.

“If someone tries to intercept [a particle] when it’s being transmitted, by touching it, they make it burst,” Gregoir Ribordy of Geneva-based quantum cryptography firm ID Quantique said last year.

The distance between Delingha and Lijiang is 1,203 kilometers, which marks a record-setting stretch over which the entangled photon pairs were transmitted. With this success, China is taking establishing itself as the absolute leader in quantum communications.

It should be noted, however, that while Micius’ achievements mark a breakthrough, we’re still pretty far from seeing a practical quantum network. Of the six million or so entangled pairs generated by Micius during each second of transmission, only one pair per second actually reached the ground-based detectors. The rest were altered by Earth’s atmosphere. Scientific American quotes Jian-Wei Pan—a physicist at the University of Science and Technology of China in Hefei who has been planning the experiment ever since 2003 — as saying “[this is like]  detecting a single photon from a lone match struck by someone standing on the moon.”

Nevertheless, this is very powerful proof of concept. Already, China has gained enough confidence to green-light more quantum communication satellites which will be tested over the next five years.

The experiment’s findings were described in the journal Science

schroedinger's cat

Physicists add another box to ‘Schrödinger’s cat’, as if one wasn’t spooky enough

It’s one of the most confusing thought experiment, but also one of the most famous in popular culture: the paradoxical state in which a cat inside a box is both alive and dead until you peer inside. Physicists at Yale University spiced things up and added a new dimension to Schrödinger’s cat by adding another box. Now, the cat is both dead and alive and sits in two boxes — all at the same time. Here goes nothing.

schroedinger's cat

Credit: Yvonne Gao, Yale University

[panel style=”panel-info” title=”What’s the deal with Schrödinger’s cat” footer=””]In 1935, in an attempt to mock the Copenhagen interpretation of quantum mechanics (hah, who got the last laugh?), Erwin Schrödinger proposed a thought experiment: a cat is placed in a sealed box along with a radioactive sample, a Geiger counter and a bottle of poison.

If the Geiger counter detects that the radioactive material has decayed, it will trigger the smashing of the bottle of poison and the cat will be killed. Effectively, the cat’s life depends on the quantum mechanically determined state of a radioactively decaying atom.

The ‘Copenhagen interpretation’ of quantum mechanics states that a particle exists in all states at once until observed. Conversely, the radioactive material can have simultaneously decayed and not decayed in the sealed environment. In follows, that Schrödinger’s cat is both alive and dead until you open the box. Of course, everyone thought this was absurd, but it’s the absurdity he was trying to convey in the first place about the Copenhagen interpretation in practical, everyday life.[/panel]

The radioactive atom and kitty are intimately “entangled” with each other. But once an observer opens the box, the “superposition” of the cat—the idea that it was in both states—would collapse into either the knowledge that “the cat is alive” or “the cat is dead,” but not both.

So, how did Yale University added another box? They paired Schrödinger’s cat with Einstein’s “spooky action at a distance” — quantum entanglement. When two particles are entangled, a change in the state of one particle is immediately reflected in the paired particle, and when I mean immediately I literally mean now. This phenomenon isn’t some weird, purely theoretical physical caveat that exists solely in the minds of awkward physicists. It’s quite practical, even. Using the power of entanglement scientists at the National Institute of Standards and Technology (NIST) instantly transferred information from on proton to another one 100 kilometers away in 2015. Physicists call this “quantum teleportation”.

Yale physicists have given Schrödinger's cat a second box to play in. Credit: Illustration by Michael S. Helfenbein/Yale University

Yale physicists have given Schrödinger’s cat a second box to play in. Credit: Illustration by Michael S. Helfenbein/Yale University

Back to the double-Schrödinger’s cat, the Yale team led by  Chen Wang devised a chamber with two small aluminum cavities fitted inside. Photons were fired that bounced in and out these cavities and a superconducting chip made of sapphire connected them through a standing wave of light. Then, in each cavity a special electronic function was induced which superimposes a standing wave of two separate wavelengths of light in each cavity. In other words, the group of photons in each cavity (the cat) oscillated at two different wave lengths at once. Because the two chambers were linked by spooky action at a distance, finding out if the cat is alive or dead required opening two boxes.

“This cat is big and smart. It doesn’t stay in one box because the quantum state is shared between the two cavities and cannot be described separately,” said Wang, a postdoctoral associate at Yale and first author of a study. “One can also take an alternative view, where we have two small and simple Schrodinger’s cats, one in each box, that are entangled.”

This is the first time anyone has proven this to work, and the findings published in the journal Science could be extremely important for quantum computers.

Where traditional computers perform their calculations in binary – using 1s and 0s – quantum computers exploit the odd characteristics of the quantum state of particles at the atomic scale. Like Schrödinger’s cat, the value of a qubit isn’t definitely 1 nor 0, but both at the same time. A quantum computer is theoretically thousands of times faster than a traditional computer.

To “solve” a calculation, the quantum state is ended, so that the qubits take a classic 1 or 0 value. Setting the quantum states and superposition up correctly should mean a quantum computer will reach the same answer as a normal one. This superposition states of particles are very fragile. Once the state is lost to “decoherence”, the data becomes corrupted and unsuable. Wang says encoding redundancy in the size of the cavity itself rather than in separate, calculated bits could help solve this problem.

“It turns out ‘cat’ states are a very effective approach to storing quantum information redundantly, for implementation of quantum error correction. Generating a cat in two boxes is the first step towards logical operation between two quantum bits in an error-correctible manner,” said co-author Robert Schoelkopf, Sterling Professor of Applied Physics and Physics, and director of the Yale Quantum Institute.

Scientists achieve quantum teleportation over 100 km

A group of scientists working at the National Institute of Standards and Technology (NIST) has managed to successfully transfer information from on proton to another one 100 kilometers away (60 miles). This could ultimately lead not to actual teleportation, but rather to unhackable conversations.

Wait, teleportation?

Most of us hear ‘teleportation’ and think ‘Beam me up, Scotty’, but quantum teleportation is very different. It relies on a phenomenon called quantum entanglement. Quantum entanglement occurs when a pair of quantum particles are generated or interact in such a way that the quantum state of each particle cannot be described independently—instead, a quantum state may be given for the system as a whole; they are entangled. Basically, when you transmit information to one, it instantly gets transmitted to the other as well – so sorry to disappoint you, but this isn’t actually physical teleportation. It can only be used for information. Albert Einstein called this “spooky action at a distance.”

Here’s an image detailing how this works:

Image via Optica.

So this type of teleportation won’t actually help with real teleportation, but will help with something called quantum encryption – it could pave the way for a new generation of security encryption. The key here is another strange quantum property: whenever a quantum state is observed, it changes. Basically, you a particle can be in both states until you actually measure it – when you measure it, it becomes either one or the other. So when two people are sharing information and a third tries to peak, it will destroy the quantum state – this makes it basically impossible to hack this type of conversations. It goes without saying that many parties are very interested in this technology. But before we can start talking about incorporating this type of encryption, we have to achieve quantum teleportation over larger and larger distances.


New theory suggests quantum entanglement and wormholes are linked together


One of the predictions derived from Einsten’s theory of general relativity is the existence of wormholes – spacetime shortcuts. In theory such bridges may offer instantaneous travel between the two bridgeheads or wormholes even if these are light-years away from each other. Two independent studies suggest that there’s a link between quantum entanglement and wormholes, or to be more precise: each wormhole has a corresponding pair just like two entangled quantum particles.

Quantum entanglement is nothing short of bizarre. In a pair of entangled particles,  a change in the quantum characteristics of one of the particles can’t happen without also causing a change in the other particle, even if these particles are millions of miles away. This concomitant change happens instantaneously, which is  why some people liken it to teleportation. I know, it’s a really strange and  non-intuitive aspect of the quantum theory of matter – this is why Einstein called it “spooky action at a distance.” For what’s it worth, although quantum entanglement was first theorized a long time ago, only recently did researchers prove that it’s real.

Practical applications for quantum entanglement have already been proposed, as entangled particles have been suggest for use in  powerful quantum computers and “impossible” to crack networks. Now, it seems quantum entanglement may be linked to wormholes.

Entangled wormholes

Theoretical physicists Juan Martín Maldacena at the Institute for Advanced Study in Princeton and Leonard Susskind at Stanford University argue that wormholes are nothing but pairs of black holes entangled together. A proposed mechanism of wormhole generation would be that when a black is born, its pair is simultaneously created as well. Moreover, they conjectured that entangled particles such as electrons and photons were connected by extraordinarily tiny wormholes.

[READ] Quantum theory suggests black holes are wormholes

Kristan Jensen, a theoretical physicist at Stony Brook University in New York and his colleague theoretical physicist Andreas Karch at the University of Washington in Seattle sought to investigate entangled particles behave in supersymmety theory which suggests that all subatomic particles have a corresponding partner or pair.

One of the biggest challenges physicists seek to address is developing a unified theory of physics, one that reconciles both general relativity and quantum mechanics. Supersymmetry is one such proposition that aims to unite the two grand theories of physics that explain the large universe (general relativity) and the tiny universe (quantum mechanics).

One huge idea expressed in this theory relates to holography or the notion that actions in this universe  may emerge from a reality with multiple dimensions; like a 2-d hologram may give the impression of 3-d object. I’d highly recommend you watch this video of Carl Sagan discussing the tesserat. Anyway, if you imagine a physical system that exists in only 3 dimensions, in theory you can describe that system using objects behaving in the four dimensions that general relativity describes the universe as having  (width, length, depth and time).

Jensen and Karch found that if one imagined entangled pairs in a universe with four dimensions, they behaved in the same way as wormholes in a universe with an extra fifth dimension.  A wormhole that curves space and time until two points coincide and entanglement may be one of the same thing then.

“Entangled pairs were the holographic images of a system with a wormhole,” Jensen said. Independent research from theoretical physicist Julian Sonner at the Massachusetts Institute of Technology supports this finding.

“There are certain things that get a scientist’s heart beating faster, and I think this is one of them,” Jensen told LiveScience. “One really exciting thing is that maybe, inspired by these results, we can better understand the relation between entanglement and space-time.”

Artist's conception shows the International Space Station in the midst of an experiment in quantum entanglement. CREDIT: ESA

Quantum entanglement experiment aboard ISS tests it over longest distance yet

Artist's conception shows the International Space Station in the midst of an experiment in quantum entanglement. CREDIT: ESA

Artist’s conception shows the International Space Station in the midst of an experiment in quantum entanglement.

One of the most mysterious, and weirdest at the same time, phenomenae in quantum physics is quantum entanglement, in which two connected particles can share information instantly despite being separated, no matter the distance. Two particles, or so the theory holds, could be parted by light years in distance and still reflect each others’ stances instantly, an oddity which prompted Einstein himself to refer to quantum entanglement as “spooky action at a distance.” Now, a group of physicists have proposed to set up an experiment aboard the International Space Station that would test quantum entanglement over the longest yet.

So far this weird display of quantum physics has only been tested in labs over relatively short distances. A while ago, ZME Science reported  how scientists used quantum entanglement to ferry photons – particles of light – over a distance of 143 kilometers, across two Canary islands. As explained in a proposal published by the Institute of Physics and the New Physics Journal, physicists now intend to triple the distance by devising an experiment on the ISS, which orbits about 400 kilometers above the planet.

“According to quantum physics, entanglement is independent of distance,” physicist Rupert Ursin of the Austrian Academy of Sciences said in a statement. “Our proposed Bell-type experiment will show that particles are entangled, over large distances — around 500 km — for the very first time in an experiment.”

Maybe you’re a bit confused by now. My recommendation is you check this youtube video embedded below for a rough, but effective explanation of this peculiar quantum effect.

The researchers suggest deploying a photon detection module to the International Space Station, where it could be attached to an existing motorized Nikon 400 mm camera lens, which observes the ground from the space station’s panoramic Cupola window. Once this setup is complete, scientists on the ground will entangle pairs of photons and send individual entangled photons to the orbiting experiment. If indeed the photon pairs are entangled, then a change to the properties of one of the particles, say that on ground, will immediately mandate the same change in its pair.

“Our experiments will also enable us to test potential effects gravity may have on quantum entanglement,” Ursin said.

If the experiment proves to be successful, then the ISS could be turned into a sort of quantum entanglement relay point in order to send a secret encryption key far above the planet’s surface, forming the basis for a worldwide quantum network. In theory, information encrypted with quantum entangled keys are unbreakable, so you can imagine the benefits and interests.

Quantum mechanics saves the day: gravity is safe for Einstein again

To be quite honest, there are moments when I feel that I don’t understand quantum mechanics at all – the phenomena involved in the field are so complex and counter intuitive one can only stop and wonder if God does in fact play dice with the Universe… but at any rate, the advancements produced by quantum mechanics are, as Einstein himself confessed, imposing. Interestingly enough, it’s quantum mechanics that helped back up one of Einstein’s most important theories.

black hole

Something which puzzled researchers in 2012 was the so-called firewall paradox; basically, this idea stated that anyone falling into a (relatively big) black hole would be burned up as they crossed the event horizon. If this were true, then it would contradict Einstein’s theory of relativity. But Professor Sam Braunstein and Dr Stefano Pirandola have helped extinguished the fire.

In a paper published in Physical Review Letters, they use quantum information theory, a modern branch of quantum mechanics that treats photons and atoms as information carriers:

“Quantum mechanics shows that [quantum] entanglement can exist across the event horizon, between particles inside and outside the black hole. But should this entanglement ever vanish, a barrier of energetic particles would be created: an energetic curtain (or firewall) would descend around the horizon of the black hole”.

Wow! Again, in all honesty, this is something very hard to wrap your head around, because the concepts involved that lead to this conclusion are so mathematically complicated that only a handful of people worldwide are able to work with them, and even understanding the principles requires a stretch.

“We are the first to show the necessity of entanglement across all black hole event horizons and to consider what happens as black holes age. The greater the entanglement, the later the curtain descends. But if the entanglement is maximal, the firewall never occurs. Indeed, entanglement has long been believed to exist for some types of black holes, taking on exactly this maximum value. Our work confirms and generalizes this claim.”

It’s important to note that their work has its basis on Stephen Hawking’s initial theory that black holes carry information, which further postulates that they harbor information about all the things they swallow:

“When quantum mechanics, and in particular entanglement, are included in the story, Hawking’s prediction holds for the longest time possible. Our results not only back up Einstein’s theory of gravity, but also point to quantum information theory as a powerful tool for disentangling the deep mysteries of the Universe.”

Long standing physics mystery apparently solved: light behaves both as particle and wave

Is light a wave, or is it made of particles? This question has puzzled since the dawn of modern physics, because somehow, light seemed to behave preferentially, depending on the situation – it was either a wave or a particle, but never both at the same time. This new quantum experiment seems to show that light can be both simultaneously, possibly creating a new dimension of modern physics which could explain the true nature of light.

Wave–particle duality postulates that all particles exhibit both wave and particle properties – a central concept in quantum mechanics. Isaac Newton advocated that light was made of particles, but then James Clerk Maxwell unified the theory of magnetism and electricity, relying on a wave model of light. But in 1905, Albert Einstein explained the photoelectric effect by proving light was a particle. So how can this be? Subsequently, depending on the tested effect, light behaved either as a particle or a wave.

Ultimately, there’s a really good reason to believe not only light, but every subatomic particle exhibits this duality, and this theory is the foundation of quantum mechanics. But the question remained: do they switch from one form to another, or are they somehow both? Now, for the first time, researchers have found a way to detect both particle and wave-like behavior at the same time.

The device relies on a process called quantum nonlocality; pretty much like every quantum phenomena, this too is counter intuitive and apparently absurd. Basically, quantum nonlocality states that a subatomic particle can exist in two places at the same time.

“The measurement apparatus detected strong nonlocality, which certified that the photon behaved simultaneously as a wave and a particle in our experiment,” physicist Alberto Peruzzo of England’s University of Bristol said in a statement. “This represents a strong refutation of models in which the photon is either a wave or a particle.”

However, the study was met with a healthy amount of criticism. MIT physicist Seth Lloyd, who was not involved in the project, called the experiment “audacious” in a related essay in Science.

“[..]if one has access to quantum memory in which to store the entanglement, the decision could be put off until tomorrow (or for as long as the memory works reliably). So why decide now? Just let those quanta slide!”

Quantum studies… they’re just weird, aren’t they?

Physicists quantum teleport photons over 143 kilometers

Last May, European scientists managed to teleport photons using quantum phenomena over a distance of 143 kilometers, across two Canary islands; however, it is only now that their paper was accepted in a peer reviewed magazine.

Beam me up, Scotty

While the technology used in Star Trek is still only science-fiction, the quantum teleportation of photons is a reality – and it definitely has its magic. The researchers, associated with the Austrian Academy of Sciences, as well as other scientific organizations made some key innovations to the already existing systems, most notably replacing optic fiber as a solution for teleportation due to signal degradation.

As Xiao-song Ma, one of the scientists involved in the experiment puts it, “The realization of quantum teleportation over a distance of 143 km has been a huge technological challenge” – and that’s putting it mildly; but the work was absolutely worth it, especially considering this can pave the way for a new age in global and extraterrestrial communication.

Lead scientist Anton Zeilinger, explained:

“Our experiment shows how mature quantum technologies are today and how useful they can be for practical applications. The next step is satellite-based quantum teleportation, which should enable quantum communication on a global scale. The next step is satellite-based quantum teleportation, which should enable quantum communication on a global scale.”

Quantum entanglement

I’ve written about quantum entanglement several times, and I still find it counter intuitive – because mostly, quantum phenomena seem illogical to our day to day, macroscopic life. The process, with direct applications in quantum computing, occurs when particles (such as photons, electrons, small molecules and even small diamonds), interact physically and then become separated. The two particles, after entangled, remain intimately connected, even when separated over vast distances – the information contained in the photon’s quantum state is transmitted from one photon to another through quantum entanglement, without actually travelling the distance. The photons remain the same until one of them is measured, which causes the receiver’s entangled particle to instantly change. Basically, when they are entangled, what you do to one of them affects the other one, regardless of distance.

In order to teleport the photon, scientists started out with three particles – two entangled, and one to be teleported; all three photons started out in the island of La Palma, and one of the particles was sent to the Canary Island of Tenerife. Here’s how the process works, quoting from Wikipedia:

1. An EPR (entangled) pair is generated and distributed to two separate locations, A and B.
2. At location A, a Bell measurement of the EPR pair qubit and the qubit to be teleported (for example, quantum state of a photon) is performed, yielding two classical bits of information. Both qubits are destroyed.
3. Using the classical channel, the two bits are sent from A to B. (This is the only potentially time-consuming step, due to speed-of-light considerations.)
4. At location B, the EPR pair qubit is modified (if necessary), using the two bits to select the correct one of four possible quantum states. A qubit identical to that chosen for teleportation (for example, quantum state of a photon) results.

The quantum internet

This is probably making your head spin, right? Quantum teleportation defeats common sense, and as a matter of fact, it makes physicists’ head spin too – especially given that matter isn’t teleported, only quantum states; but it’s extremely useful, and could bring a myriad of advancements in numerous fields.

“The quantum internet is predicted to be the next-generation information processing platform, promising secure communication and an exponential speed-up in distributed computation,” the researchers write in a paper detailing their experiment published online Wednesday in the journal Nature.

What this means is you could potentially send messages throughout the entire solar system, like maybe start talking to the base you just set up on Mars, or keep in touch with those robots you sent on asteroids to mine platinum. Or even more, you could create instantaneous internet connections. But all that is a long time from happening.

“The future goal of our research work will be to do such experiments on the satellite level,” Ma explained. “This will enable intercontinental quantum information exchange.”

Scientific source: Nature

Quantum computers will be able to simulate particle collisions [w/ video]

Quantum computers could answer numerous extremely complicated questions, impossible to unlock at the moment

Effective quantum computers are still far away, but researchers are already showing more and more advantages these devices would bring to the table. A trio of theorists have shown one more talent of a quantum computer: it would be powerful enough to study the inner workings of the universe in ways that are far beyond the reach of even the most powerful conventional supercomputers.

Storing quantum information in atoms or using qubits is already a thing of the present, but quantum computers still require technologies that will likely be perfected in a few decades. The genius move here is building processors that rely on quantum mechanics instead of classical mechanics – these laws allow quantum switches to exist in both on and off simultaneous, thus being able to consider all the possible solutions at once.

Graphical representation of particle collisions

Aside from bringing us some really cool and fast computers, it will also enable scientists to create some incredibly powerful quantum computers, which will be able to answer some of the biggest questions at the moment.

“We have this theoretical model of the quantum computer, and one of the big questions is, what physical processes that occur in nature can that model represent efficiently?” said Stephen Jordan, a theorist in NIST‘s Applied and Computational Mathematics Division. “Maybe particle collisions, maybe the early universe after the Big Bang? Can we use a quantum computer to simulate them and tell us what to expect?”

Questions such as this one involve keeping track of multiple elements and analyzing all their possible interactions, something which is just too much for today’s supercomputers. However, the team developed an algorithm that could run on any quantum computer, regardless of the specific technology which will be eventually used to build it. The algorithm would simulate all the possible interactions between two elementary particles colliding with each other, something that currently requires years of effort and a large accelerator to study.

Simulating these collisions is an enormously difficult problem for today’s digital computers because the quantum state of the colliding particles is very complex and, therefore, difficult to represent accurately with a feasible number of bits which only work with 0 and 1. The team’s algorithm, however, encodes the information that describes this quantum state far more efficiently using an array of quantum switches, making the computation far more reasonable.

Quantum entanglement

“What’s nice about the simulation is that you can raise the complexity of the problem by increasing the energy of the particles and collisions, but the difficulty of solving the problem does not increase so fast that it becomes unmanageable,” Preskill says. “It means a quantum computer could handle it feasibly.”

Even though their algorithm showed only one type of collision, they believe their work paves the way for exploring the entire theoretical foundation on which fundamental physics rests.

“We believe this work could apply to the entire standard model of physics,” Jordan says. “It could allow quantum computers to serve as a sort of wind tunnel for testing ideas that often require accelerators today.”

Via Physorg

Dual channel allows electrons to maintain phase; states are denoted by arrows (credit: Andreas Wieck)

Scientists devise qubits in a semiconductor for the first time

Hailed as yet another big step towards devising working quantum computers, scientists at Ruhr-Universität Bochum (RUB) have successfully managed to generate quantum qubits inside a semiconductor for the first time, instead of vacuum.

Dual channel allows electrons to maintain phase; states are denoted by arrows (credit: Andreas Wieck)

Dual channel allows electrons to maintain phase; states are denoted by arrows (credit: Andreas Wieck)

A qubit is the quantum analog of a bit. While a bit must be read either as a 0 or 1, the qubit can be read as 0, as 1 or both states at the same time, known as a superposition. What really sets a qubit apart from your typical bit, though, is quantum entanglement, which is a form of superposition, but not quite. The video below this paragraph explains very well what quantum entanglement is all about better than I ever could. It’s suffice to say, however, that quantum entanglement is a must have prerequisite for quantum computation which can not be rendered effectively with a classical computer. It’s entanglement that allows a qubit to have complex variables assigned to it, which scientists believe will significantly one day increase the computation power, and in doing so will open a portal to a new realm of quantum research, currently impossible.

Back to the breakthrough research at hand, physicist Prof. Dr. Andreas Wieck and colleagues were able to use the trajectories of an electron through two closely spaced channels for encoding qubits in a semiconductor. For a qubit to be preserved it’s imperative that the electron wave doesn’t disperse and loses its ability to encode information, the case when traveling through a solid. To tackle this issue, the scientists applied a solution proposed by Wieck some 22 years ago, consisting of a high-purity gallium arsenide crystal marked by dual channels.

These dual channels allow electrons to move through a tunnel on well defined parallel paths, which ensures the electron wave doesn’t travel through different paths and preserves phase information. Only one single electron fits through at a time, until they reach a fork. At this fork, two electrons take the same path simultaneously and merge, causing an electron waves to interfere each other and, in some occasions, cause qubits with more than one state to form. Currently, only a small percentage of the fired electrons emerge as qubits, but the researchers hope to increase its efficiency.

“Unfortunately, not all the electrons take part in this process, so far it’s only a few percent,” commented Wieck. “Some students in my department are, however, already working on growing crystals with higher electron densities.”

The scientists’ findings were published in the journal Nature Nanotechnology.

via Kurzweil AI

Artist's impression of the quantum photonic chip, showing the waveguide circuit (in white), and the voltage-controlled phase shifters (metal contacts on the surface).

Quantum computing breakthrough: quantum photonic chip created

Artist's impression of the quantum photonic chip, showing the waveguide circuit (in white), and the voltage-controlled phase shifters (metal contacts on the surface).

Artist's impression of the quantum photonic chip, showing the waveguide circuit (in white), and the voltage-controlled phase shifters (metal contacts on the surface).

Scientists at University of Bristol‘s Centre for Quantum Photonics have remarkably managed to create a multi-purpose optical chip capable of manipulating and measuring quantum entanglement and mixture – two important quantum effects which have been giving researchers headaches for a long time, but which can now be controlled and used to characterize quantum circuits. This is a considerable leap forward in the race for developing the first working quantum computer.

Controlling quantum entanglement, a phenomenon which describes the interaction of two distant particles as a pair, is fundamental to developing  quantum computers. Bristol researchers have shown that this phenomenon can be generated, manipulated, and most importantly, measured all on a tiny silica chip.

“In order to build a quantum computer, we not only need to be able to control complex phenomena such as entanglement and mixture, but we need to be able to do this on a chip, so that we can scalably and practically duplicate many such miniature circuits—in much the same way as the modern computers we have today,” says Professor Jeremy O’Brien, Director of the Centre for Quantum Photonics. “Our device enables this and we believe it is a major step forward towards optical quantum computing.”

The chip, measuring a mere 70 mm by 3 mm, consists of a network of tiny channels which guide, manipulate and interact single photons in a sequence of operations which would ordinarily be carried out on an optical bench the size of a large dining table. Using eight reconfigurable electrodes embedded in the circuit, photon pairs can be manipulated and entangled, producing any possible entangled state of two photons or any mixed state of one photon.

“It isn’t ideal if your quantum computer can only perform a single specific task. We would prefer to have a reconfigurable device which can perform a broad variety of tasks, much like our desktop PCs today — this reconfigurable ability is what we have now demonstrated,” says Peter Shadbolt, lead author of the study.

[RELATED] The age of nano-electronics: scientists develop one of the world’s smallest circuits

“This device is approximately ten times more complex than previous experiments using this technology. It’s exciting because we can perform many different experiments in a very straightforward way, using a single reconfigurable chip.”

The quantum photonic chip is the product of six years of hard work development, and now researchers are hoping they can scale and replicate it such that they might build the building block for the future’s long sought quantum computers.

“Being able to generate, manipulate and measure entanglement on a chip is an awesome achievement,” says Dr Terry Rudolph from Imperial College in London, UK,.

“Not only is it a key step towards the many quantum technologies — such as optical quantum computing — which are going to revolutionize our lives, it gives us much more opportunity to explore and play with some of the very weird quantum phenomena we still struggle to wrap our minds around.”


Physicists use humans to detect quantum effects

The quantum world is entirely different from what we see around us; it has its own laws, its own algebra, etc. It’s a really bizarre place, but that can yield wonderous developments as well. Since the quantum laws are so different, it’s hard to actually observe them, so instead, thought experiments are used. But for the first time, that has changed – researchers have used humans to actually observe the results of a quantum phenomena.

Quantum entanglement

Nicolas Gisin, a physicist at the University of Geneva in Switzerland created a test to see is human eyes can detect signs of entanglement. Quantum entanglement is a really weird and unexplainable fact, outside the quantum world: it practically links two or more objects in such a way that if you measure one’s properties, the other one’s properties are changed, no matter how far away they are from each other. Doesn’t make much sense does it ? But that’s how it goes in the quantum world. Quantum effects such as this one are typically limited to the microscopic world and are observed only through precise microscopes, thus indirectly.

He was inspired by an experiment carried out in Rome; professor Fabio Sciarrino and his team at La Sapienza University in Rome entangled a pair of photons and then ‘amplified’ one of them to create a shower of thousands of photons with the same quantum state.

“I immediately realized that the human eye could see that many photons,” says Gisin.

Making quantum visible for the naked eye

So he used a similar line-up, they entangled two photons; one of them was sent through a standard photon detector, while the other one was amplified using a machine that generated photons with the same polarization, and thus, at least in theory, generating a quantum micro-macro entanglement.

But here Gisin did something differently – he replaced the photon light field detector with a human. The beam of light produced by the amplifier could appear in one of two positions, and the location of the beam reflected the polarization state of the photons in the field. Gisin and his team sat in the dark for hours, marking the position of the light spot over repeated runs of the experiment, for the first time seeing the effects of quantum entanglement with the naked eye.

After a long and hard day’s work, they got the results they expected; the human results were double checked with photon detectors, and the results were positive, even though the latter were “faster and more reliable than humans and didn’t complain of tiredness”, according to Gisin.

A false positive

But the thing is, what they saw was not micro-macro entanglement. According to the laws of quantum physics, the act of measurement would break the entanglement, and thus the first photon and the light field could not be entangled (again, this goes against common sense).

“We set up the worst kind of amplifier precisely to see what result the standard Bell test would give, and it gave the wrong — positive — answer,” says Gisin.

The Bell test is the most common test to check the state of entanglement. According to Gisin, the reason for this false positive is that no detector is perfect, and some photons will always be lost during the experiment. Normally, this does not affect the Bell test, but Gisin says that as more photons come into play, the loophole hugely distorts the results. So regardless of the actual result, the Bell test would always be positive.

“This is brilliant work showing that if we do not control everything in the experiment, we can be fooled into thinking we have seen a macroscopic quantum effect, when we haven’t,” says Magdalena Stobińska, a quantum physicist at the Max Planck Institute for the Science of Light in Erlangen, Germany.

Sciarrino was not surprised by the results, and he says he already knew the Bell test couldn’t be fully trusted in such cases. Nevertheless, he applaudes the experiment.

“The experiment is lovely because in this sense you can ‘see’ entanglement,” says Sciarrino. “It brings quantumness closer to human experience.”