Physics

Physicists Reverse The Flow Of Time Using Quantum Computer

An algorithm that simulates sending a particle back in time opens up new avenues for exploring the backward flow of time in quantum frameworks. It may also facilitate developing new methods for program testing and error correction on quantum computers.

Everything in this observable universe is governed by entropy. The “arrow of time” – the change you see every day: progression of things from order to disorder – that’s entropy in play. We cannot reverse it.

But, in a first-of-its-kind experiment, a consortium of physicists led by the U.S. Department of Energy’s (DOE) Argonne National Laboratory have successfully managed to return a particle briefly to the past. How did they do it?

Going back in time may actually be possible. Researchers have reversed the flow of time by fraction of a second using IBM’s quantum computer.

To achieve time reversal, the team developed an algorithm specifically tailored for IBM’s quantum computer that can simulate particle scattering.

One of the best classical representation of this is rolling of a billiard ball across the table after being struck by a cue. When you take this to a quantum level, the ball is spread in multiple directions moving around at different speeds. To reverse this in quantum term means sending all the ball(s) back to its original position.

Restoring something back to its original state is impossible in nature. In essence, we can’t restore a shattered teacup to its original form, or erase wrinkles that keep popping up as we age. But if we want to break this particular law of physics, we would need to be able to properly manipulate the particle’s quantum waves at every point. And for that, we would need something called a ​”supersystem,” or external force.

Researchers pointed out that the timeline required for such system to appear and manipulate the quantum waves would take inconceivable amount of time. In order words, it would take longer than the universe itself which is pretty disheartening for the physicists.

Undeterred by the setback, the team then looked for ways to overcome this complexity, at least in principle. Their algorithm appear to be the only option, so they brought IBM computer into play and set it to simulate an electron scattering.

The algorithm launched the electron from a localized, (seen state) to a scattered one. It then threw the process in reverse, returning the electron to its initial state. In other words, the electron was sent back in time for a tiny fraction for a second.

The algorithm was proven to work 85 percent of the time in a two-qubit quantum computer.

The team did what was once considered impossible, and this astonishing feat of their intellect have pushed our understanding of the second law of thermodynamics to new heights. Earlier, we didn’t know if the law of entropy could be manipulated or broken in the quantum world. But now, we at least have a slender idea of the function of the second law of thermodynamics within its realm.

“The results also give a nod to the idea that irreversibility results from measurement, highlighting the role that the concept of​ ‘measurement’ plays in the very foundation of quantum physics,” explained coauthor Gordey Lesovik of the Moscow Institute of Physics and Technology in a news release.

The team have yet to envisage all the implications the findings can have, but one thing for sure: it can lend a hand on researchers to build a better quantum computers. You know, like, the one that can perform “program testing and error correction” by itself.  

Source: U.S. Department of Energy’s (DOE) Argonne National Laboratory 

Reference: Arrow of time and its reversal on the IBM quantum computer (Scientific Reports)

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