Two-photon tomography using on-chip quantum walks

TL;DR

This paper introduces a novel quantum tomography method leveraging quantum walks and spatial photon correlations in photonic circuits, enabling full reconstruction of two-photon states without tunable elements, suitable for on-chip integration.

Contribution

It presents a new approach to quantum tomography using quantum walks and spatial correlations, eliminating the need for tunable elements and facilitating on-chip implementation.

Findings

Enables full reconstruction of two-photon states

Utilizes spatial photon correlations in quantum walks

Compatible with on-chip superconducting detectors

Abstract

We present a conceptual approach to quantum tomography based on first expanding a quantum state across extra degrees of freedom and then exploiting the introduced sparsity to perform reconstruction. We formulate its application to photonic circuits, and show that measured spatial photon correlations at the output of a specially tailored discrete-continuous quantum-walk can enable full reconstruction of any two-photon spatially entangled and mixed state at the input. This approach does not require any tunable elements, so is well suited for integration with on-chip superconducting photon detectors.