A clock moving in superposition of different speeds would measure a superposition of different elapsing times in a quantum version of the famous twin paradox of special relativity. Credit: Magdalena Zych

More accurate clocks and sensors may result from a recently proposed experiment, linking an Einstein-devised paradox to quantum mechanics.

University of Queensland physicist Dr. Magdalena Zych said the international collaboration aimed to test Einsteins twin paradox using quantum particles in a superposition state.

The twin paradox is one of the most counterintuitive predictions of relativity theory, Dr. Zych said. It says that time can pass at different speeds for people at different distances to an enormous mass or traveling with different velocities.

For example, relative to a reference clock far from any massive object, a clock closer to a mass or moving at high speed will tick slower. This creates a twin paradox, where one of a pair of twins departs on a fast-speed journey while the other stays behind. When the twins reunite, the traveling twin would be much younger, as different amounts of time have passed for each of them.

Its a mind-blowing effect featured in popular movies like Interstellar but its also been verified by real world experiments, and is even taken into consideration in order for everyday GPS technology to work.

The team included researchers from the University of Ulm and Leibniz University Hannover and found how one could use advanced laser technology to realize a quantum version of Einsteins twin paradox.

In the quantum version, rather than twins there will be only one particle traveling in a quantum superposition.

A quantum superposition means the particle is in two locations at the same time, in each of them with some probability, and yet this is different to placing the particle in one or the other location randomly, Dr. Zych said.

Its another way for an object to exist, only allowed by the laws of quantum physics.

The idea is to put one particle in superposition on two trajectories with different speeds, and see if a different amount of time passes for each of them, as in the twin paradox. If our understanding of quantum theory and relativity is right, when the superposed trajectories meet, the quantum traveler will be in superposition of being older and younger than itself.

This would leave an unmistakable signature in the results of the experiment, and thats what we hope will be found when the experiment is realized in the future.

It could lead to advanced technologies that will allow physicists to build more precise sensors and clocks potentially, a key part of future navigation systems, autonomous vehicles and earthquake early-warning networks.

The experiment itself will also answer some open questions in modern physics.

A key example is, can time display quantum behavior or is it fundamentally classical? Dr. Zych said. This question is likely crucial for the holy grail of theoretical physics: finding a joint theory of quantum and gravitational phenomena. Were looking forward to helping answer this question, and tackling many more.

For more on this study, read Physicists Put Einstein to the Test With a Quantum-Mechanical Twin Paradox.

Reference: Interference of clocks: A quantum twin paradox by Sina Loriani, Alexander Friedrich, Christian Ufrecht, Fabio Di Pumpo, Stephan Kleinert, Sven Abend, Naceur Gaaloul, Christian Meiners, Christian Schubert, Dorothee Tell, tienne Wodey, Magdalena Zych, Wolfgang Ertmer, Albert Roura, Dennis Schlippert, Wolfgang P. Schleich, Ernst M. Rasel and Enno Giese, 4 October 2019, Science Advances.DOI: 10.1126/sciadv.aax8966

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