Sprecher
Beschreibung
Recent progress in photonic quantum experiments has led to widespread use of photon-number-resolving detectors, often described as measurements with many possible outcomes. But what does it mean, operationally, for such a detector to genuinely resolve the number of photons? A device may produce many output labels while being a much coarser measurement followed by classical post-processing. In this sense, the raw number of reported outcomes is not by itself a reliable notion of measurement resolution.
I will discuss a definition of genuine resolution for quantum measurements, based on outcome simulability. A measurement is said to have resolution at most k if its statistics can be simulated by measurements with at most k outcomes, together with arbitrary classical post-processing and shared randomness. Measurements that are not simulable in this way are therefore genuinely higher-resolution. This provides an operational definition of resolution that is independent of a particular detector model.
I will then show how this definition leads to a simple certification protocol. In a prepare-and-measure state discrimination game, one can upper-bound the guessing probability achievable by all measurements of resolution at most k. Observing a larger value certifies that the measurement has genuine resolution larger than k. Finally, I will describe an implementation using coherent-state probes of a superconducting nanowire photon-number-resolving detector, where the method certifies genuine four-outcome resolution. The result gives a way to turn informal claims of photon-number resolution into an experimentally testable operational statement.
Paper link: https://arxiv.org/abs/2606.14365