Time-reversal of an unknown quantum state

TL;DR

This paper presents a method to reverse the temporal evolution of any unknown quantum state, advancing the understanding of quantum irreversibility and enabling universal time-reversal algorithms on quantum computers.

Contribution

It introduces a procedure for reversing the evolution of arbitrary unknown quantum states, extending previous work limited to known or disentangled states.

Findings

Successfully demonstrated reversal of unknown quantum states on quantum hardware.

Established a universal approach for quantum time reversal applicable to arbitrary states.

Enhanced understanding of quantum irreversibility and measurement effects.

Abstract

For decades, researchers have sought to understand how the irreversibility of the surrounding world emerges from the seemingly time symmetric, fundamental laws of physics. Quantum mechanics conjectured a clue that final irreversibility is set by the measurement procedure and that the time reversal requires complex conjugation of the wave function, which is overly complex to spontaneously appear in nature. Building on this Landau-Wigner conjecture, it became possible to demonstrate that time reversal is exponentially improbable in a virgin nature and to design an algorithm artificially reversing a time arrow for a given quantum state on the IBM quantum computer. However, the implemented arrow-of-time reversal embraced only the known states initially disentangled from the thermodynamic reservoir. Here we develop a procedure for reversing the temporal evolution of an arbitrary unknown quantum state. This opens the route for general universal algorithms sending temporal evolution of an arbitrary system backwards in time.