Minimum Disturbance Measurement without Post-Selection

TL;DR

This paper introduces a linear optical device capable of performing optimal quantum measurements on a single-photon polarization qubit without post-selection, achieving minimal disturbance while fully utilizing all detection events.

Contribution

The work presents the first deterministic, postselection-free implementation of minimum disturbance measurement on a single-photon qubit using linear optics.

Findings

Device achieves optimal information-disturbance trade-off

All detection events are used without postselection

Experimental results confirm theoretical predictions

Abstract

We propose and demonstrate a linear optical device which deterministically performs optimal quantum measurement or minimum disturbance measurement on a single-photon polarization qubit with the help of an ancillary path qubit introduced to the same photon. We show theoretically and experimentally that this device satisfies the minimum disturbance measurement condition by investigating the relation between the information gain (estimation fidelity) and the state disturbance due to measurement (operation fidelity). Our implementation of minimum disturbance measurement is postselection-free in the sense that all detection events are counted toward evaluation of the estimation fidelity and the operation fidelity, i.e., there is no need for coincidence postselection of the detection events.