World's 'most accurate and precise' atomic clock developed

US scientists have developed an atomic clock that is understood to be more precise and accurate than any clock previously created. The clock was built by researchers at JILA — a joint institution of the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder — and submitted to the journal Physical Review Letters.

While existing-generation atomic clocks shine microwaves on atoms to measure the length of a second, next-generation atomic clocks illuminate atoms with visible light waves, which have a much higher frequency, to count out the second much more precisely. Compared with current microwave clocks, optical clocks are expected to deliver much higher accuracy for international timekeeping — potentially losing only one second every 30 billion years. But in order to achieve such high accuracy, these clocks need to have very high precision; in other words, they must be able to measure extremely tiny fractions of a second.

The JILA clock uses a web of light known as an ‘optical lattice’ to trap and measure tens of thousands of individual atoms simultaneously, providing a huge advantage in precision — the more atoms measured, the more data the clock has for yielding a precise measurement of the second. Compared with previous optical lattice clocks, the JILA researchers used a shallower, gentler web of laser light to trap these atoms, which significantly reduced two major sources of error — effects from the laser light that traps the atoms, and atoms bumping into one another when they are packed too tightly.

According to JILA physicist Jun Ye, the new clock is so precise that it can detect tiny effects predicted by theories such as general relativity, even at the microscopic scale. General relativity is Einstein’s theory that describes how gravity is caused by the warping of space and time, with one of its key predictions being that time itself is affected by gravity — the stronger the gravitational field, the slower time passes.

The new clock design can allow detection of relativistic effects on timekeeping at the submillimetre scale, about the thickness of a single human hair. Raising or lowering the clock by that minuscule distance is enough for researchers to discern a tiny change in the flow of time caused by gravity’s effects. This ability to observe the effects of general relativity at the microscopic scale can significantly bridge the gap between the microscopic quantum realm and the large-scale phenomena described by general relativity.

More precise atomic clocks also enable more accurate navigation and exploration in space. As humans venture further into the solar system, clocks will need to keep precise time over vast distances. Even tiny errors in timekeeping can lead to navigation errors that grow exponentially the further you travel.

“If we want to land a spacecraft on Mars with pinpoint accuracy, we’re going to need clocks that are orders of magnitude more precise than what we have today in GPS,” Ye said. “This new clock is a major step towards making that possible.”

The same methods used to trap and control the atoms could also produce breakthroughs in quantum computing. Quantum computers need to be able to precisely manipulate the internal properties of individual atoms or molecules to perform computations. The progress in controlling and measuring microscopic quantum systems has significantly advanced this endeavour.

By venturing into the microscopic realm where the theories of quantum mechanics and general relativity intersect, researchers will soon be able to achieve new levels of understanding about the fundamental nature of reality itself. From the infinitesimal scales where the flow of time becomes distorted by gravity, to the vast cosmic frontiers where dark matter and dark energy hold sway, the new clock’s ultrahigh precision promises to illuminate some of the universe’s deepest mysteries.

“We’re exploring the frontiers of measurement science,” Ye said. “When you can measure things with this level of precision, you start to see phenomena that we’ve only been able to theorise about until now.”

Image caption: An extremely cold gas of strontium atoms is trapped in a web of light known as an optical lattice. The atoms are held in an ultrahigh-vacuum environment, which helps preserve the atoms’ delicate quantum states. The red dot you see in the image is a reflection of the laser light used to create the atom trap. Image credit: K Palubicki/NIST.