Undoing a quantum measurement

TL;DR

This paper demonstrates a method to deterministically reverse a complete quantum measurement on a single particle using a quantum error-correction protocol involving three particles, challenging the notion that measurements are inherently irreversible.

Contribution

It introduces a protocol for reversing a fully projective quantum measurement on a single particle through quantum error correction with three particles.

Findings

Successful deterministic reversal of a quantum measurement

Implementation of quantum error correction to undo measurement effects

Potential implications for quantum information processing and error correction

Abstract

In general, a quantum measurement yields an undetermined answer and alters the system to be consistent with the measurement result. This process maps multiple initial states into a single state and thus cannot be reversed. This has important implications in quantum information processing, where errors can be interpreted as measurements. Therefore, it seems that it is impossible to correct errors in a quantum information processor, but protocols exist that are capable of eliminating them if they affect only part of the system. In this work we present the deterministic reversal of a fully projective measurement on a single particle, enabled by a quantum error-correction protocol that distributes the information over three particles.