Physics

New Time Dilation Phenomenon Revealed: Timekeeping Theory Combines Quantum Clocks and Einstein’s Relativity

Time Dilation Illustration

Quantum mechanics allows for a clock to move as if it were simultaneously traveling at two different speeds. New research finds that this leads to a correction in atomic clocks known as “quantum time dilation.” Credit: Petra Korlevic

A phenomenon of quantum mechanics known as superposition can impact timekeeping in high-precision clocks, according to a theoretical study from Dartmouth College, Saint Anselm College and Santa Clara University.

Research describing the effect shows that superposition — the ability of an atom to exist in more than one state at the same time — leads to a correction in atomic clocks known as “quantum time dilation.”

The research, published today (October 23, 2020) in the journal Nature Communications, takes into account quantum effects beyond Albert Einstein’s theory of relativity to make a new prediction about the nature of time.

“Whenever we have developed better clocks, we’ve learned something new about the world,” said Alexander Smith, an assistant professor of physics at Saint Anselm College and adjunct assistant professor at Dartmouth College, who led the research as a junior fellow in Dartmouth’s Society of Fellows. “Quantum time dilation is a consequence of both quantum mechanics and Einstein’s relativity, and thus offers a new possibility to test fundamental physics at their intersection.”

In the early 1900s, Albert Einstein presented a revolutionary picture of space and time by showing that the time experienced by a clock depends on how fast it is moving — as the speed of a clock increases, the rate at which it ticks decreases. This was a radical departure from Sir Isaac Newton’s absolute notion of time.

Quantum mechanics, the theory of motion governing the atomic realm, allows for a clock to move as if it were simultaneously traveling at two different speeds: a quantum “superposition” of speeds. The research paper takes this possibility into account and provides a probabilistic theory of timekeeping, which led to the prediction of quantum time dilation.

To develop the new theory, the team combined modern techniques from quantum information science with a theory developed in the 1980s that explains how time might emerge out of a quantum theory of gravity.

“Physicists have sought to accommodate the dynamical nature of time in quantum theory for decades,” said Mehdi Ahmadi, a lecturer at Santa Clara University who co-authored the study. “In our work, we predict corrections to relativistic time dilation which stem from the fact that the clocks used to measure this effect are quantum mechanical in nature.”

In the same way that carbon dating relies on decaying atoms to determine the age of organic objects, the lifetime of an excited atom acts as a clock. If such an atom moves in a superposition of different speeds, then its lifetime will either increase or decrease depending on the nature of the superposition relative to an atom moving at a definite speed.

The correction to the atom’s lifetime is so small that it would be impossible to measure in terms that make sense at the human scale. But the ability to account for this effect could enable a test of quantum time dilation using the most advanced atomic clocks.

Just as the utility of quantum mechanics for medical imaging, computing, and microscopy, might have been difficult to predict when that theory was being developed in the early 1900s, it is too early to imagine the full practical implications of quantum time dilation.

Reference: “Quantum clocks observe classical and quantum time dilation” by Alexander R. H. Smith and Mehdi Ahmadi, 23 October 2020, Nature Communications.
DOI: 10.1038/s41467-020-18264-4

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  • I've always wondered how scientists actually measure the movement they are talking about, isn't that relative also. Think about it the Earth is spinning on its axis, also around the sun all the sun also is moving in the galaxy and our galaxy is expanding, so where and how are you measuring movement?

    • Yes, it's all relative. The cosmic microwave background has been used as a proxy for a universal reference frame, as have distant quasars, but strictly speaking, there is no such thing.

    • The relativistic point of reference is relative to the observers. There is no one absolute reference point.

      If we use a point on the equator it will give a different result that a point like the Greenwich Naval Observatory - due to differences in angular momentum due to a difference in latitude on the rotating globe.

    • You really don't need to. It's relative motion. Generally, you have one object at a relativistic speed and one that's not.

  • Terry Pratchett wrote a book about making the most precise clock. It turned out to be the Auditors trying to wipe out humans again. Hmmm...they found Earth.

  • You question is excellent! The answer may surprise you. All motions of any kind are measured with respect to something else, i.e. they are relative motions. There is no such thing as "absolute motions: except in two cases. The first is Newtonian which just says when you apply a force to a body it will accelerate and therefore move faster than it was and that is a type of absolute motion reference frame but only for accelerations. Motions including this one must still be measured relative to something else. Now here's the kicker, Relativity does give us an absolute motion measurement because light from any object in motion must always travel at exactly C no matter from what reference frame it is measured. This gets into time dilation of one reference frame to another and the result is every reference frame see C exactly as the same absolute speed measure, but this is very much complicated by any time dilations operant at each reference frame. So in fact although C is an absolute speed measurement indecent of any reference frame, it can not be used to get around measuring any bodies traveling less than C must be measured relative to each other. But its not so bad, almost everything is measured astrophysically as the speed relative to the Earth so at least the same reference frame is used so speeds can be compared. An interesting one to consider is a satellite orbiting the Earth; at what speed is it moving? By Newton's inverse square law of gravity the orbital speed is fixed by the mass of the object orbited but it is always the relative speed with respect to the object orbited. Now imagine lots of orbits within the solar system. Like you said everything moves so everything above applies but the relative speed of say a orbiting satellite is as stated above but it can also be calculated relative to any other body for example the sun which is traveling also within the galaxy. Not a simple situation! But that's the way it works. The study of all this is called Celestial Mechanics and that is an extremely complicated and endeavor but essential for space travel among the planets. Hope this helps and give you some grounds for future thoughts.

  • Quantum time dilation is only speculation here and must be measured and confirmed which as it says is almost impossible. Frankly relative motion between two quantum probability wave functions resulting in time dilation is kind of a nutty idea. But if it proves out it would be very interesting. (Lots of people have been trying to merge the Quantum with Relativity. That may not be necessary. Case in point, very precise measurements of the old Newtonian gravity law between quantum atomic particles have been carried out with extreme precision and no deviation from Newton's very old prediction has been found as a result of measurement between these quantum particles. The two laws could coexist as a mesh and both operate as they do with one not affecting the other at all as in this example. Nature obeys its laws without care of man's desires.)

  • A quantum superposition of infinite spacetime fields in General Relativity! What a terrifying, awe-inspiring thought.

  • I am enjoying this article,as a "layman" it is difficult to fully understand. I am learning. That's the wonderful part.

  • "...the time experienced by a clock depends on how fast it is moving" is a bit misleading. It implies that the clock really does slow down. It doesn't - not from its own point of view.

    We normally define reality as how things are from their own POV. If we want to use a different POV we should make this clear:

    "....the ticking-rate of a clock appears to slow down depending on how fast we are moving relative to it."

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