Simultaneously sorting overlapping quantum states of light

TL;DR

This paper demonstrates a novel optical device that can simultaneously sort overlapping quantum states of light encoded in spatial modes, enabling improved quantum measurement and image classification.

Contribution

The authors develop a multi-plane light converter capable of efficiently sorting non-orthogonal, overlapping light states in a single step, advancing quantum state discrimination techniques.

Findings

Successfully sorted states in dimensions from 3 to 7

Achieved simultaneous discrimination and basis change

Potential applications in quantum communication and image recognition

Abstract

The efficient manipulation, sorting, and measurement of optical modes and single-photon states is fundamental to classical and quantum science. Here, we realise simultaneous and efficient sorting of non-orthogonal, overlapping states of light, encoded in the transverse spatial degree of freedom. We use a specifically designed multi-plane light converter (MPLC) to sort states encoded in dimensions ranging from $d = 3$ to $d = 7$. Through the use of an auxiliary output mode, the MPLC simultaneously performs the unitary operation required for unambiguous discrimination and the basis change for the outcomes to be spatially separated. Our results lay the groundwork for optimal image identification and classification via optical networks, with potential applications ranging from self-driving cars to quantum communication systems.