Friday 18 October 2019

Physicists manage to 'turn back time' in experiment

Dr Who: Sci-fi time traveller is played now by Jodie Whitaker
Dr Who: Sci-fi time traveller is played now by Jodie Whitaker

John von Radowitz

It may not quite be the Tardis, but scientists have built what could loosely be described as a time machine.

In an experiment that would have challenged Doctor Who, researchers defied the second law of thermodynamics, which governs the direction of "time's arrow" from past to future.

Working in the realm of quantum mechanics, they achieved the equivalent of causing a broken rack of pool balls to re-order itself. It was as if the balls scattered randomly around a pool table went into reverse and packed themselves back into their original triangle formation.

To an observer, it looks as if time is running backwards.

Lead researcher Dr Gordey Lesovik, who heads the Laboratory of the Physics of Quantum Information at the Moscow Institute of Physics & Technology (MIPT), said: "We have artificially created a state that evolves in a direction opposite to that of the thermodynamic arrow of time."

The "time machine" described in the journal 'Scientific Reports' is based around a quantum computer that carries out calculations using basic elements known as superconducting "qubits".

A qubit is a unit of information described by a "one", a "zero", or a mixed "superposition" of both states.

In the experiment, an "evolution programme" was launched which caused the qubits to become an increasingly complex changing pattern of zeros and ones. During this process, order was lost - just as it is when the pool balls are struck and scattered with a cue. Uncertainty ruled the system as it does when balls fly randomly to different corners of a pool table. Another programme then modified the state of the quantum computer in such a way that it evolved "backwards", from chaos to order.

The state of the qubits was rewound back to its original starting point. An analogy would be giving the pool table such a perfectly calculated kick that the balls roll back into an orderly triangle.

Irish Independent

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