Anomalous weak values via a single photon detection

Is it possible that a measurement of a spin component of a spin-1/2 particle yields the value 100? In 1988 Aharonov, Albert and Vaidman argued that upon pre- and postselection of particular spin states, weakening the coupling of a standard measurement procedure ensures this paradoxical result(1). This theoretical prediction, called weak value, was realised in numerous experiments(2-9), but its meaning remains very controversial(10-19), since its anomalous nature, i.e., the possibility to exceed the eigenvalue spectrum, as well as its quantumness are debated(20-22). We address these questions by presenting the first experiment measuring anomalous weak values with just a single click, without the need for statistical averaging. The measurement uncertainty is significantly smaller than the gap between the measured weak value and the nearest eigenvalue. Beyond clarifying the meaning of weak values, demonstrating their non-statistical, single-particle nature, this result represents a breakthrough in understanding the foundations of quantum measurement, showing unprecedented measurement capability for further applications of weak values to quantum photonics.

Automated summary

The study presents the first experiment to measure anomalous weak values with a single click, showing non-statistical nature of weak values and clarifying their meaning in quantum measurement. This breakthrough enhances understanding of the foundations of quantum measurement and demonstrates unprecedented measurement capability for further applications in quantum photonics.