Purification of noisy quantum measurements

TL;DR

This paper explores methods to enhance noisy quantum measurements by preprocessing strategies, including error correction-like procedures for finite-dimensional systems and preamplification for unbounded observables, aiming to emulate ideal detectors.

Contribution

It introduces novel preprocessing techniques for noisy quantum measurements, enabling near-perfect measurement of observables in finite-dimensional systems and unbounded spectrum scenarios.

Findings

Preprocessing can make many noisy detectors equivalent to a single ideal detector.

Error correction-like strategies enable perfect measurement with increasing detectors.

Preamplification effectively purifies measurements with unbounded spectra.

Abstract

We consider the problem of improving noisy quantum measurements by suitable preprocessing strategies making many noisy detectors equivalent to a single ideal detector. For observables pertaining to finite-dimensional systems (e.g. qubits or spins) we consider preprocessing strategies that are reminiscent of quantum error correction procedures and allows one to perfectly measure an observable on a single quantum system for increasing number of inefficient detectors. For measurements of observables with unbounded spectrum (e.g. photon number, homodyne and heterodyne detection), the purification of noisy quantum measurements can be achieved by preamplification as suggested by H. P. Yuen [1].