Physicists make time travel possible using quantum computer

In a breakthrough study, researchers have managed to reverse time using a quantum computer. The scientists from the US and Russia have demonstrated time reversal by sending a qubit (the basic unit of quantum information) from a complicated state to a simpler form, reports Newsweek.

The suggested algorithm alters the quantum developed state which then starts to develop in reverse. "Doing this magic with the developed state of ink we will see that after the same time (time needed for the dissolving of ink in the water) the ink will again combine back into the original drop," study author Andrei Lebedev told the outlet. "This is exactly what we did in our work where the drop of ink is state of three qubits, and the water is a Hilbert state of the quantum computer."

"This is one in a series of papers on the possibility of violating the second law of thermodynamics. That law is closely related to the notion of the arrow of time that posits the one-way direction of time: from the past to the future," said Gordey Lesovik, lead author of the study.

The experiment included setting each qubit's state to what is believed to be zero. From that point, the qubits take a more complex form, transforming to a pattern of zeros and ones. Then an advanced program lets the quantum computer go from a state of fringe to order. The process of going from complex to simply send the qubits backward in time.

Around 85 percent of the times the program was successful in a two quantum computer. However, the introduction of a third qubit caused more errors and the success rate plummeted to 50 percent.

So making a quantum computer that could go back in time on a large scale doesn't seem to be happening any time soon. Also, it shows that time reversal could be unlikely as it is too complex to pull off.

"Such an unfortunate growth of the complexity explains why do we not observe such time-reversed objects in the Nature," Lebedev said. "The probability of a spontaneous appearance of a time-reversed object (particle of a system of particles) is negligible."
However, the process could come in handy to test quantum computer programs. "In quantum computation, unlike the classical analog, we cannot interrupt the computation process until the very end."

"The problem is that a quantum computer is in the superposition state and if we interrupt it and measure its state we destroy this superposition and project it into one component with some probability."

"Because of that it is not always obvious to verify what at the end of the computation we get is the correct result... Time reversal can help-we do time-reversal of the final state of the computer and run the same quantum program again. If the computation was correct we will arrive to the initial state of the computer."