Experimental demonstration of direct path state characterization by strongly measuring weak values in a matter-wave interferometer

TL;DR

This paper demonstrates a method for quantum state characterization using both strong and weak measurements in a matter-wave interferometer, showing strong interactions can outperform weak ones in accuracy.

Contribution

It introduces an experimental scheme for direct quantum state measurement employing strong interactions, challenging the notion that only weak measurements are effective.

Findings

Strong interactions outperform weak interactions in state characterization.

The method is applicable beyond neutron interferometry to various quantum systems.

Experimental evidence supports the effectiveness of strong measurements.

Abstract

A novel method was recently proposed and experimentally realized for characterizing a quantum state by directly measuring its complex probability amplitudes in a particular basis using so-called weak values. Recently Vallone and Dequal showed theoretically that weak measurements are not a necessary condition to determine the weak value [Phys. Rev. Lett. 116, 040502 (2016)]. Here we report a measurement scheme used in a matter-wave interferometric experiment in which the neutron path system's quantum state was characterized via direct measurements using both strong and weak interactions. Experimental evidence is given that strong interactions outperform weak ones. Our results are not limited to neutron interferometry, but can be used in a wide range of quantum systems.