Single-shot detection limits of quantum illumination with multi-qudit states

TL;DR

This paper investigates the detection limits of quantum illumination using multi-qudit states, revealing how entanglement configurations influence performance and identifying the optimal states for target detection in noisy environments.

Contribution

It introduces an analysis of multi-qudit states for quantum illumination, showing that specific entanglement patterns optimize detection performance under noise.

Findings

Entanglement between signal and idler qubits enhances detection.

Entanglement between signal qubits degrades performance.

Optimal states are non-maximally entangled bipartite states.

Abstract

Quantum illumination is a protocol for detecting a low-reflectivity target by using two-mode entangled states composed of signal and idler modes, which can outperform unentangled states. We study multi-qudit states for single-shot detection limits of quantum illumination under white noise environment. Using three-qubit states, we obtain that the performance is enhanced by the entanglement between signal and idler qubits, whereas it is degraded by the entanglement between signal qubits. The similar behaviors are also observed for three-qutrit, four-qubit, and four-ququart states. In particular, the optimal state is not a maximally entangled multipartite state but a combination of a maximally entangled bipartite state. Moreover, we show that quantum correlation can explain the quantum advantage of three-qubit, three-qutrit, and four-qubit states, with exception of a four-ququart state.