A new, more accurate atomic clock could help detect dark objects and study the effects of Gravity on Time

Pressing a laser atomic clock

Atoms locked in an optical pile are made up of two mirrors. When a “tension” laser is passed through the pile, the atoms engage, and the frequency is measured with a second laser, as a platform for more precise atomic clocks. Reputation: permission of the researchers

The new atomic clock design, which uses connected atoms, could help scientists find dark matter and study the effects of gravity in time.

Atomic clocks are the most accurate timekeepers in the world. These elegant instruments use lasers to measure the vibration of the atoms, which oscillate at a constant frequency, as many microscopic beams float in synchronization. The best atomic clocks in the world hold time so accurately that, if they had run from the beginning of the universe, they would only be off for about half a second today.

However, they could be even more precise. If atomic clocks could more accurately measure atomic vibrations, they would be sensitive enough to detect onions as a dark material and gravity waves. With better atomic clocks, scientists could also begin to bend some questions, such as the potential effect of gravity on the movement of time and whether time itself changes as the universe- who ages.

Now a new type of atomic clock designed by MIT physics can allow scientists to study such questions and perhaps publish new physics.

The researchers report today in the journal Nature that they have built an atomic clock that measures not a cloud of random oscillating atoms, as modern design now measures, but instead atoms that were largely entangled. The atoms are connected in a way that is impossible according to the laws of classical physics, and allows scientists to measure the vibration of atoms more accurately.

The new setup can achieve the same error four times faster than clocks without engaging.

“Advanced atomic optical clocks will have the ability to deliver better accuracy in one second than modern optical clocks,” says lead author Edwin Pedrozo-Peñafiel, postdoc of MIT’s electronic research lab.

If modern atomic clocks were modified to measure connected atoms as the position of the MIT team does, their time would improve so that, over the entire age of the universe, the clocks would be less than 100 milliseconds off.

Other co-authors of the paper from MIT are Simone Colombo, Chi Shu, Albert Adiyatullin, Zeyang Li, Enrique Mendez, Boris Braverman, Akio Kawasaki, Saisuke Akamatsu, Yanhong Xiao, and Vladan Vuletic, Professor of Physics Lester Wolfe.


Since people began to observe the movement of time, they have done so using occasional onions, such as the movement of the sun across the sky. Today, vibrations in atoms are the most stable seasonal events that scientists can observe. In addition, one cesium atom oscillate at the same frequency as another cesium atom.

To keep time perfect, it would be best if clocks were to monitor the oscillations of a single atom. But at that scale, an atom is so small that it carries it according to the secret rules of quantum mechanics: When weighed, it behaves like coins that only take averages over many flips. This limitation is what physicists refer to as the Standard Quantum Standard.

“When you increase the number of atoms, the average of those atoms goes to something that gives the right value,” says Colombo.

That is why today’s atomic clocks are designed to measure gas of thousands of the same type of atom, to estimate their average oscillations. A typical atomic clock does this by first using a system of lasers to charge gas of ultracooled atoms into a laser-generated trap. A second stationary laser, with a frequency close to the vibration of the atoms, is placed to monitor atomic inflation and thus monitor time.

And yet, the Universal Concentration Level still works, meaning that there is still some uncertainty, even among thousands of atoms, about the exact individual frequency. This is where Vuletic and its group have shown that quantum entry could help. In general, quantum engagement describes a non-classical physical state, in which atoms in a group show the results of correlational measurements, even if each individual atom behaves as if tossing a coin at random.

The team reasoned that if atoms became involved, their individual oscillations would fluctuate around a common frequency, with less bias than if they were not involved. Thus the average oscillations that an atomic clock would measure would certainly be higher than the Standard Quantum limit.

Clocks attached

In their new atomic clock, Vuletic and his colleagues engage about 350 atoms of ytterbium, which oscillate at the same very high frequency as visible light, resulting in one an atom animates 100,000 times more frequently in one second than a cesium. If ytterbium oscillations can be closely monitored, scientists can use the atoms to identify smaller intervals.

The group used standard methods to cool the atoms and capture them in an optical cavity formed by two mirrors. They then passed a laser through the optical cavity, where it connected between the mirrors, interacting with the atoms thousands of times.

“Light is like a communication link between atoms,” Shu explains. “The first atom that sees this light changes the light slightly, and that light also changes the second atom, and the third atom, and through many circles, the atoms both know each other. and start the same behavior. ”

In this way, the researchers first engage the atoms, and then use another laser, similar to the existing atomic clocks, to measure the average frequency. When the team ran a similar test without interfering with atoms, they found that the atomic clock with attached rectangular atoms arrived four times faster.

“You can always make the clock more accurate by measuring longer,” Vuletic says. “The question is, how long do you need to reach a certain precision. A lot of surprises have to be measured on fast timescales. ”

He says that if today ‘s modern atomic clocks can be modified to measure atoms that are largely involved, not only would they hold better time, but they could help by determining symptoms in the universe such as dark matter and gravitational waves, and begin to answer some age questions.

“As the universe ages, does the speed of light change? Does the cost of the electron change? ”Vuletic says. “You can study with more accurate atomic clocks.”

Fact: “Engaging in atomic clock optical transition” by Edwin Pedrozo-Peñafiel, Simone Colombo, Chi Shu, Albert F. Adiyatullin, Zeyang Li, Enrique Mendez, Boris Braverman, Akio Kawasaki, Daisuke Akamatsu, Yanhong Xiao and Vladan Vuletić, 16 December 2020, Nature.
DOI: 10.1038 / s41586-020-3006-1

This research was supported, in part, by DARPA, the National Science Foundation, and the Naval Research Office.