Discrimination and identification of quantum states

Masashi Ban

Francesco Buscemi, Massimiliano F. Sacchi

We propose two experimental schemes for quantum state discrimination that achieve the optimal tradeoff between the probability of correct identification and the disturbance on the quantum state.

Francesco Buscemi, Massimiliano Federico Sacchi

Abstract. We propose two experimental schemes for quantum state discrimination that achieve the optimal tradeoff between the probability of correct identification and the disturbance on the quantum state. 1.

János A. Bergou

Daeho Yang

Abstract Object identification is central to modern sensing, widely employed in autonomous systems and industrial inspection. However, conventional approaches rely on image formation followed by computational inference, requiring many photons to suppress shot noise and introducing readout and computational latencies. These limitations arise because direct position-basis measurement is not optimized for discriminating object-encoded states. Here, we demonstrate single-photon object identification without imaging by implementing quantum state discrimination in a high-dimensional spatial Hilbert space. By applying a task-optimized unitary transformation prior to wavefunction collapse, we transform spatially overlapping object-encoded wavefields into spatially separated states. Thus, the measurement basis is engineered so that the collapse of the single-photon state directly specifies the object label. Numerically, our method achieves 90.2% identification accuracy for nine objects, surpassing the 31.9% classical limit obtained from maximum-likelihood single-photon intensity imaging. Experimentally, the framework achieves 71.0% conditional identification accuracy under attenuated coherent illumination with camera detection, and is further demonstrated with heralded single photons using only 36 detection channels. Our framework establishes a quantum-measurement approach to information-efficient sensing that connects quantum state discrimination with computational optics, providing a route toward low-photon and ultrafast object identification.

真弓 八野, Fumiaki Shibata