Scientists claim to have 'reversed time' with quantum computer

James Marshall
March 14, 2019

In a development that also represents a major advance in our understanding of quantum computers, by using electrons and the odd world of quantum mechanics, researchers were able to turn back time in an experiment that is the equivalent of causing a broken rack of pool balls to go back into place.

The research includes Lead researcher Dr Gordey Lesovik, head of the Laboratory of the Physics of Quantum Information at the Moscow Institute of Physics & Technology (MIPT) who was helped by colleagues in Switzerland and the US.

Most laws of physics do not make a distinction between the past and future, but the scientists claim that their experiment, which involved "reversing time", showed that these laws can be violated.

The so-called "time machine" is made up of electron qubits. Within the framework of statistical physics, this problem was inextricably associated with the Second Law of Thermodynamics, which declares that entropy growth proceeds from the system's entanglement with the environment.

During this process, order was lost - just as it is when the pool balls are struck and scattered with a cue. This doesn't mean we'll be visiting with dinosaurs or Napoleon any time soon, but for physicists, the idea that time can run backward at all is still a pretty big deal. The system will always tend toward disorder.

Most other laws of physics do not prevent rolling billiard balls from assembling into a pyramid, infused tea from flowing back into the tea bag, or a volcano from "erupting" in reverse.

Scientists were keen to know if time could spontaneously reverse itself at least for an individual particle and for a tiny fraction of a second. In this way, they follow the laws of quantum mechanics, which are less clear-cut than the classical world humans inhabit.

To an outside observer, it looks as if time is running backwards. A qubit is a unit of information described by a zero, one or can be a mix of both the states in which case it becomes a superposition. They found that even if they studied 10 billion electrons every second, it would take the lifetime of the universe for such a phenomenon to happen just one time. "Mathematically, it means that under a certain transformation, called complex conjugation, the equation will describe a "smeared" electron localizing back into a small region of space over the same time period".

As the time machine is described in the Scientific Reports consists of a quantum computer which is made up of electron qubits. Provided that the "kick" has been delivered successfully, the program does not result in more chaos but rather rewinds the state of the qubits back into the past, the way a smeared electron would be localized or the billiard balls would retrace their trajectories in reverse playback, eventually forming a triangle. Following this scattering, a program would alter the computer's state, enabling it to go backwards to its original state.

The new experiment is like giving the pool table such a perfectly calculated kick that the balls rolled back into an orderly pyramid.

Stage 4: Regeneration. The evolution program from the second stage is launched again.

According to the team, in 85 percent of cases, the two-qubit quantum computer returned back into its original state. The scientists said the error rate is anticipated to drop as more devices are designed.

"Another fundamental question is whether it is possible at all to design a quantum algorithm that would perform time-reversal more efficiently".

Dr Lesovik added: "Our algorithm could be updated and used to test programmes written for quantum computers and eliminate noise and errors".

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