Nothing saves time like the beating heart of an atom. But even the sharp touch-touch of the vibrating nucleus is limited by the uncertainties imposed by the laws of quantum mechanics.
A few years ago, researchers at MIT and the University of Belgrade in Serbia proposed that quantum entanglement could push clocks beyond that blurred limit.
We now have a proof of concept in the form of an experiment. Physicists connected a cloud of ytterbium-171 aters with streams of photons reflected from a surrounding mirror room and measured the timing of their tiny swings.
Their results show that entanglement of atoms in this way could speed up the time-measurement process of atomic nucleus clocks, making them more accurate than ever. In principle, a clock based on this new approach would lose only 100 milliseconds from the dawn of time.
Similar to other avant-garde clocks based on the nuclei of cesium and thorium atoms, time in this type of configuration is divided by oscillations into an ytterbium nucleus after absorbing a specific light energy.
Since the ytterbium nucleus can be hummed at a speed 100,000 times faster than the nucleus of a cesium atom, it provides a much more accurate time maintenance mechanism.
But there comes a time when quantum physics says that it is impossible to say exactly where the oscillations of an atom begin and stop. This standard quantum limit (SQL) acts as a blur in the atomic pendulum; you may have a faster clock, but what good is it if you can’t measure it?
Without a way to overcome this hurdle, it really doesn’t matter if we change a set of atomic nuclei for a more precise type: their quantum disorder sets a hard limit on the accuracy of atomic clocks.
A trick is to record the frequencies of multiple atoms that hum at the same time in a network of hundreds of tiny atomic pendulums. Current atomic clock technologies use lasers designed to be as stable as possible, providing each atom with a very similar light frequency. Combining collective blur, an average of individual uncertainties occur.
This new method goes a step further in this average process. By connecting atoms in a way that entangles the quantum probabilities of their turns, it is possible to redistribute the uncertainty of the system, increasing accuracy in some parts at the expense of others.
“It’s like light serves as a communication link between atoms,” says MIT physicist Chi Shu.
“The first atom that sees this light will slightly modify the light, and this light also modifies the second atom and the third atom, and through many cycles, the atoms know each other collectively and begin to behave similarly.”
Regardless of the method used, the longer you listen, the more accurate the end result will be. In this case, the team found that the interlacing made the measurement process three times faster compared to clocks operating in SQL.
This may not sound so dramatic, but an increase in speed may be just what we need to study some of the most subtle influences the Universe has in time.
“As the Universe ages, does the speed of light change? Does the charge of the electron change?” says lead researcher Vladan Vuletic of MIT.
“That’s what you can probe with more accurate atomic clocks.”
It might even allow us to find the point at which general relativity falls apart, pointing to a new physics that connects the definite curvature of space-time with the uncertain nature of quantum fields. Or allow us to better measure the fine characteristics of temporary deformation of dark matter.
Located on the brink of a new era in physics and astronomy, we will really need time on our side.
This research was published in Nature.