Reversing the Weak Quantum Measurement for a Photonic Qubit

TL;DR

This paper demonstrates the conditional reversal of weak quantum measurements on photonic qubits using linear optics, achieving over 94% fidelity, and explores the role of reversal as information erasure.

Contribution

It presents the first experimental implementation of reversing weak quantum measurements on photonic qubits with high fidelity.

Findings

State recovery fidelity exceeds 94% for partial-collapse strength up to 0.9

Weak measurement causes nonunitary transformation of the qubit

Reversal operation effectively erases information gained from the weak measurement

Abstract

We demonstrate the conditional reversal of a weak (partial-collapse) quantum measurement on a photonic qubit. The weak quantum measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state after a successful reversing operation. Both the weak measurement and the reversal operation are implemented linear optically. The state recovery fidelity, determined by quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.