Testing sequential quantum measurements: how can maximal knowledge be extracted?

TL;DR

This paper experimentally investigates the balance between information gain and disturbance in sequential quantum measurements, demonstrating an adaptive strategy that optimizes this trade-off for two measurements, with implications for extending to multiple measurements.

Contribution

It introduces an experimental analysis of sequential partial quantum measurements and demonstrates an adaptive approach to optimize the information-disturbance trade-off.

Findings

Adaptive measurement strategies improve the information-disturbance trade-off.

Optimal trade-offs can be achieved in a single measurement process.

Results can be extended to multiple sequential measurements.

Abstract

The extraction of information from a quantum system unavoidably implies a modification of the measured system itself. It has been demonstrated recently that partial measurements can be carried out in order to extract only a portion of the information encoded in a quantum system, at the cost of inducing a limited amount of disturbance. Here we analyze experimentally the dynamics of sequential partial measurements carried out on a quantum system, focusing on the trade-off between the maximal information extractable and the disturbance. In particular we consider two different regimes of measurement, demonstrating that, by exploiting an adaptive strategy, an optimal trade-off between the two quantities can be found, as observed in a single measurement process. Such experimental result, achieved for two sequential measurements, can be extended to N measurement processes.