Direct and Efficient Detection of Quantum Superposition

TL;DR

This paper introduces a resource-efficient method using XOR games to verify quantum superposition with high confidence through local measurements, avoiding the need for recombination of states.

Contribution

It adapts XOR games for superposition verification, enabling efficient, high-confidence detection with minimal copies and local measurements, a novel approach in quantum resource verification.

Findings

Achieved 99% confidence in superposition detection with 37 photon copies.

Demonstrated exponential approach to certainty in superposition verification.

Showed XOR games can verify quantum resources without reinterfering states.

Abstract

One of the most striking quantum phenomena is superposition, where one particle simultaneously inhabits different states. Most methods to verify coherent superposition are indirect, in that they require the distinct states to be recombined. Here, we adapt an XOR game, in which separated parties measure different parts of a superposed particle, and use it to verify superpositions with \textit{local measurements} and a second independent particle. We then turn this game into a resource-efficient verification scheme, obtaining a confidence that the particle is superposed which approaches unity exponentially fast. We demonstrate our scheme using a single photon, obtaining a 99\% confidence that the particle is superposed with only 37 copies. Our work shows the utility of XOR games to verify quantum resources, allowing us to efficiently detect quantum superposition without reinterfering the superposed states.