Tag Archives: atomic clock

Credit: NIST.

New atomic clocks could measure distortions in space-time itself

Scientists have made optical atomic clocks that ‘tick’ a quadrillion times a second, making them accurate enough to potentially measure the gravitational distortion of space-time across the Earth’s surface more precisely than current methods. In the future, this sort of atomic ticker could be used to detect gravitational waves, test general relativity, and even search for dark matter.

Credit: NIST.

Credit: NIST.

The flow of time is not absolute — it is relative, as we’ve come to know thanks to Einstein’s work. When you’re having fun, times flies in a breeze and, conversely, when we’re faced with a daunting task, it seems to take forever. But this is merely our subjectivity playing tricks on us. What’s more remarkable is that even seemingly objective measures of time, such as the swing of a finely-tuned pendulum, can be relative. For instance, a clock placed on Mt. Everest will tick slightly faster than the same clock at sea level due to the effects of the gravity potential.

In order to compare and sync clocks at different points in a gravity field, we’re forced to establish a common reference surface. For planet Earth, this is the geoid — the surface of equal gravitational potential representing the global-mean sea level. Today, the geoid is determined by altimetry measurements performed by satellites and physical models of the planet’s gravity. Both approaches have limitations that introduce uncertainties of several centimeters. With atomic clocks, these imprecisions could become minimal.

Physicists at the National Institute of Standards and Technology (NIST) recently demonstrated one such device — an optical atomic clock that traps a thousand ytterbium atoms in optical lattices (grids made of laser beams). An analog clock measures a second as the complete oscillation of a pendulum, for instance. An atomic clock is not all that different in principle, vibrating between two energy levels to produce a ‘tick’. According to findings published in the journal Naturethe authors were able to set three records in systematic uncertainty (how well the clock represents natural vibrations), stability (how much the clock’s frequency changes), and reproducibility (how closely two atomic clocks tick at the same frequency).

The atomic clocks, which are the size of a tabletop, matched the natural frequency to within a possible error of just one billionth of a billionth. A clock pair had a frequency difference below 10-18  and the frequency change over a specific time interval was only  3.2 x 10-19, over a day. For such a clock to lose a second it would take longer than the age of the universe, currently estimated at 13.8 billion years.

The ytterbium clocks could one-day measure how Earth’s gravity slows time, thus offering a way to pinpoint the clock’s location in the planet’s gravitational field to within a centimeter. The researchers plan on performing a test with clocks in two separate locations in order to determine their accuracy.

Among its many applications, the new atomic clocks could be used to detect ripples in spacetime called gravitational waves or even in the hunt for dark matter — the elusive form of matter that our instruments cannot detect but which scientists are almost certain it exists due to the gravity it exerts throughout the universe. The ytterbium clocks could also be used for the future redefinition of the second — the international unit of time. The clock records meet one of the international redefinition roadmap’s requirements, a 100-fold improvement in validated accuracy over the best clocks based on the current standard, the cesium atom.

What PTB's transportable optical atomic clock looks like inside the trailer. Credit: Physikalisch-Technische Bundesanstalt (PTB).

Scientists use mobile optical atomic clocks in the field for the first time (and this is a big deal)

What PTB's transportable optical atomic clock looks like inside the trailer. Credit: Physikalisch-Technische Bundesanstalt (PTB).

What PTB’s transportable optical atomic clock looks like inside the trailer. Credit: Physikalisch-Technische Bundesanstalt (PTB).

One of the most delicate clocks in the world was recently taken for a spin by European scientists. For the first time, a transportable optical atomic clock has been used to make measurements in the field. Experts hope that this proof of concept will pave the way for a wide adoption of mobile atomic clocks around the world, vastly reducing costly errors in engineering and construction projects, but also helping research in climate or geophysics.

Atom o’clock

Optical atomic clocks represent the state-of-the-art in the frontier of modern measurement science (metrology). All clocks tell the time using a stable oscillator, whether we’re talking about a grandfather clock, which is based on a pendulum, or a sundial clock, which relies on the planet’s rotation. In an optical atomic clock, the oscillator is a laser which is regulated by the quantum oscillations of atoms. These are the most precise clocks in existence today, employing lasers with frequencies in the 100s of terahertz range. This means that these clocks ‘tick’ about a quadrillion (one million billion) times per second.

Extremely precise atomic clocks are of great interest to scientists who investigate dark matter and dark energy. Atomic clocks are also indispensable in some highly sensitive tools like gravitational wave telescopes. When gravitational waves pass through a region of space, they change the frequency of light waves traveling through the same region, but very so slightly. An optical clock can detect this slight change in light frequency and measure the effect of the gravitational wave. 

Researchers from the National Physical Laboratory (NPL), the Physikalisch-Technische Bundesanstalt (PTB) and the Istituto Nazionale di Ricerca Metrologica (INRIM) used their transportable optical atomic clock to measure the gravity potential difference between the exact location of the clock positioned in the middle of the Fréjus road tunnel between France and Italy and a second clock at INRIM, which is 90 km away in Torino, Italy. The height difference between the two clocks is about 1,000 meters.

To accurately compare the readings of the two clocks, the researchers set up a 150 km-long optical fiber link and employed a frequency comb to connect the clocks to the link. To verify the optical atomic clock measurements, the researchers also determined the gravity potential difference using more conventional methods like geodetic techniques. The two types of measurements were found to be consistent.

“Optical clocks are deemed to be the next generation of atomic clocks—operating not only in laboratories but also as mobile precision instruments,” said Christian Lisdat, group leader at PTB.

Of course, this isn’t exactly a wristwatch. The on-the-road optical atomic clock is pretty large, occupying much of the volume of a vibration-damped and temperature-stabilized trailer.

Researchers alongside the trailer that transported the atomic clock. Credit: PTB.

Researchers alongside the trailer that transported the atomic clock. Credit: PTB.

This sort of mobile optical atomic clock has the potential to resolve height differences as small as 1 cm across the planet’s surface. One of the biggest advantages of optical clocks is that they can take measurements at specific locations whereas satellite-based measurements average the gravity potential over lengths of about 100 km. As such, mobile optical atomic clocks positioned through all sorts of locations can lead to much higher-resolution measurements of the planet’s gravity potential.

A high-res map of Earth’s gravity potential would allow scientists to monitor sea levels and the dynamics of ocean currents with unparalleled accuracy — and all in real time. Researchers could also track seasonal trends in ice sheet masses and overall ocean mass changes, vastly improving the reliability of climate models and weather forecasts.

Optical atomic clocks could also save the industry billions by solving inconsistencies between national height systems. For instance, engineers who worked on the Hochrhein Bridge between Germany and Switzerland used different sea level calculations for each side, which lead to a 54cm level gap between the two sides.

“Our proof-of-principle experiment demonstrates that optical clocks could provide a way to eliminate discrepancies and harmonise measurements made across national borders. One day, such technology could help to monitor sea level changes resulting from climate change,” said Helen Margolis, fellow in optical frequency standards and metrology at NPL.

Scientific reference: Jacopo Grotti et al, Geodesy and metrology with a transportable optical clock, Nature Physics (2018). DOI: 10.1038/s41567-017-0042-3.

Nuclear clocks will keep track of time at an unprecedented level of accuracy. The white rabbit from Alice in Wonderland would have most likely been interested in this research.

Nuclear clocks set to become most accurate timekeepers on Earth. Only a fraction of a second lost for 14 billion years

Nuclear clocks will keep track of time at an unprecedented level of accuracy. The white rabbit from Alice in Wonderland would have most likely been interested in this research.

Nuclear clocks will keep track of time at an unprecedented level of accuracy. The white rabbit from Alice in Wonderland would have most likely been interested in this research.

Atomic clocks are the current most accurate time and frequency standards, capable of operating with an uncertity of only a second in millions of years. A new research currently in the work by scientist from the University of New South Wales seeks to track time with an unprecedented accuracy of a mere 20th a second in 14 billion years, 100 times more accurate than an atomic clock.

Atomic clocks work by tracking the orbit of electrons, essentially using them as a sort of pendulum. The researchers suggest they can reach a  hundredfold increase in accuracy by employing an alternate solution. They propose using lasers to orient the electrons in an atom in such a manner that the clock could actually track neutrons orbiting around the atom’s nucleus. The proposed single-ion clock, or nuclear clock, would thus be accurate to 19 decimal places or by a twentieth of a second over 14 billion years, roughly the age of the Universe.

Electrons are subjected to slight external interference, which cause a meager, yet important,  inaccuracy in atomic clocks. Neutrons orbit extremely close to the nucleus, which makes them almost immune to interference. Currently, atomic clocks are the world’s timekeeping standard, and are widely used in a range of applications, from GPS navigation systems, to high-bandwidth data transfer, to govermental timing synchronization, to system synchronization in particle accelerators, where even a nanosecond error needs to be cleared.

“This is nearly 100 times more accurate than the best atomic clocks we have now,” says professor Victor Flambaum of the University of New South Wales.

“It would allow scientists to test fundamental physical theories at unprecedented levels of precision and provide an unmatched tool for applied physics research.”

No word has been given so far concerning when the researchers will actually build the first nuclear clock, however their findings are expected to be published in an upcoming paper in the journal It’s not clear just yet if or when the researchers plan to construct such a clock, but their findings are set to be published in the industry journal Physical Review Letters

US and Russia researchers working together made most precise clock ever

Time is money, time is of the essence, it’s time for time to be given its just attention; clocks are already incredibly precise, but with this new improvement, they will be just incredible ! Researchers from America and Russia announced that they have eliminated a source of error that came from temperature variation and they have increased the accuracy of the clocks until the point that the maximum error is one second every 32 billion years – which is older than the universe.

Back in time

Humans have measured time since the ancient days, and there is evidence of some time-measuring tools thousands of years ago. The first relatively modern clock however, dates from the 13th century; they no longer exist, but incredibly precise descriptions of them have been found – precise enough to confirm that these clocks were functioning rather well.

However, as the decades and then centuries passed, clockmakers developed and perfected their art (as it was considered); the race to build smaller watches was of course hot, and it was technically challenging. Some focused on reliability and accuracy; and some just wanted to make prettier watches.

The first patent for a watch was released on November 17, 1797, Eli Terry received his first patent for a clock. Terry is known as the founder of the American clock-making industry. Scottish clockmaker Alexander Bain received the pattent for the first electric watch in 1840. As the technological surge continued in the 20th century, watches began to lack clockwork components entirely; instead, they measured time using the behaviour of quartz crystals, the vibration of a tuning fork, or even the quantum response of some atoms.

Atomic clocks

Atomic clocks are the most accurate we have so far – yes, they are as hi-tech as they sound; they function by analyzing electronic frequency transmissions in the microwave, optical, or ultraviolet region of the electromagnetic spectrum of atoms as a frequency standard for its timekeeping element. However, the accuracy of these clocks is dependant on the temperature of the atoms used, so this was pretty much the only source of error that could appear.

The errors, of course, were extremely small, but precision timekeeping is one of the pillars of modern science and technology, and time measuring plays an extremely important role in some fields of science.

“Using our calculations, researchers can account for a subtle effect that is one of the largest contributors to error in modern atomic timekeeping,” says lead author Marianna Safronova of the University of Delaware, the first author of the presentation. “We hope that our work will further improve upon what is already the most accurate measurement in science: the frequency of the aluminum quantum-logic clock,” adds co-author Charles Clark, a physicist at the Joint Quantum Institute, a collaboration of the National Institute of Standards and Technology (NIST) and the University of Maryland.

What the team studied was an effect that pretty much everybody knows – at least everybody who has ever been at a campfire: heat radiation. Everything around you emits radiation (called blackbody radiation, or BBR), and even isolated atoms feel and exchange temperature with the surrounding environment. This quantum-logic clock, based on atomic energy levels in the aluminum ion, Al+, has an potential error of 1 second per 3.7 billion years.

In order to correct for the BBR shift, and reduce the potential errors, the team used the quantum theory of atomic structure to calculate the BBR shift of the atomic energy levels of the aluminum ion.