A single programmable photonic circuit for universal quantum measurements

TL;DR

This paper presents a scalable, programmable photonic quantum measurement device capable of performing arbitrary measurements, surpassing traditional projective measurement limits and enhancing quantum information processing tasks.

Contribution

It introduces a universal, integrated photonic measurement processor that enables arbitrary quantum measurements within a scalable circuit framework, a key advancement in quantum photonics.

Findings

Achieved an average fidelity of 97.7% in measurement tomography.

Demonstrated superior performance in quantum tasks: lower error in state discrimination, higher fidelity in state estimation, and increased randomness generation.

Validated the device's capability to perform universal quantum measurements beyond projective limits.

Abstract

Programmable photonic quantum processors face a critical challenge: despite significant advances in quantum state preparation and manipulation, measurements remain limited to projective techniques. Here, we demonstrate a programmable measurement processor that overcomes this limitation by enabling arbitrary quantum measurements within a scalable circuit framework. Our large-scale integrated photonic architecture achieves precise coherent control of ancillary quantum systems, realizing a universal four-dimensional quantum measurement device. We benchmark the processor by performing measurement tomography on 100 randomly selected measurements, achieving an average fidelity of 97.7%. The processor's performance exceeds the theoretical limits of projective measurements in three key quantum information tasks: state discrimination (with 23 times lower error), state estimation (with 10.6% higher fidelity), and randomness generation (with 37% more randomness yield), demonstrating its high operational quality. This work establishes a fully programmable quantum measurement processor, advancing the development of universal quantum operations for photonic quantum information processing by providing the key missing component.