Beyond one: Indian researchers’ experiment could lead to a new tool for quantum measurement

Researchers at the Raman Research Institute (RRI), an autonomous institute of the Department of Science and Technology (DST), have conducted the first experimental measurement of a quantum measure exceeding one, bringing Quantum Measure Theory (QMT) into the laboratory. By constructing an 'event-filter' utilizing photon routes, polarization, and subsequent erasure of distinguishing information to allow interference, the team measured a quantum measure of approximately 1.17, which agrees with theoretical predictions. While detector probabilities remain below one, the quantum measure can exceed one due to wave interference between different photon routes. This development could potentially lead to new tools for quantum measurement and computing.