Experimental observation of anomalous weak value without post-selection

TL;DR

This paper experimentally demonstrates that anomalous weak values can be observed without post-selection by performing sequential weak measurements on a single-qubit system, revealing new insights into measurement processes.

Contribution

It shows that anomalous weak values are observable without post-selection through sequential measurements, challenging previous beliefs and expanding understanding of weak measurement phenomena.

Findings

Anomalous weak value observed without post-selection in single-qubit system.

Measurement strength controlled via hologram density on spatial light modulator.

Anomalous weak value disappears with strong measurement strength.

Abstract

Weak measurement has been shown to play important roles in the investigation of both fundamental and practical problems. Anomalous weak values are generally believed to be observed only when post-selection is performed, i.e, only a particular subset of the data is considered. Here, we experimentally demonstrated an anomalous weak value can be obtained without discarding any data by performing a sequential weak measurement on a single-qubit system. By controlling the blazing density of the hologram on a spatial light modulator, the measurement strength can be conveniently controlled. Such an anomalous phenomenon disappears when the measurement strength becomes strong. Moreover, we find that the anomalous weak value can not be observed without post-selection when the sequential measurement is performed on each of the components of a two-qubit system, which confirms that the observed anomalous weak value is based on sequential weak measurement of two noncommutative operators.