Arrow of time and its reversal on IBM quantum computer

TL;DR

This paper demonstrates that, contrary to natural irreversibility, a quantum algorithm can reverse time evolution in a quantum system, experimentally shown on an IBM quantum computer with electron scattering.

Contribution

The authors design a quantum algorithm that performs complex conjugation, enabling time reversal of quantum states, and experimentally demonstrate backward time dynamics on a real quantum device.

Findings

Quantum algorithm for time reversal using complex conjugation.

Experimental demonstration of backward time dynamics on IBM quantum computer.

Reversal of electron scattering process in a quantum system.

Abstract

Uncovering the origin of the arrow of time remains a fundamental scientific challenge. 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. It remains to be seen, however, whether the irreversibility of time is a fundamental law of nature or whether, on the contrary, it might be circumvented. Here we show that, while in nature the complex conjugation needed for time reversal is exponentially improbable, one can design a quantum algorithm that includes complex conjugation and thus reverses a given quantum state. Using this algorithm on an IBM quantum computer enables us to experimentally demonstrate a backward time dynamics for an electron scattered on a two-level impurity.