Witnessing trustworthy single-photon entanglement with local homodyne measurements

Abstract

Single-photon entangled states, i.e. states describing two optical paths sharing a single photon, constitute the simplest form of entanglement. Yet they provide a valuable resource in quantum information science. Specifically, they lie at the heart of quantum networks, as they can be used for quantum teleportation, swapped and purified with linear optics. The main drawback of such entanglement is the difficulty in measuring it. Here, we present and experimentally test an entanglement witness allowing one not only to say whether a given state is path-entangled but also that entanglement lies in the subspace where the optical paths are each filled with one photon at most, i.e. refers to single-photon entanglement. It uses local homodyning only and relies on no assumption about the Hilbert space dimension of the measured system. Our work provides a simple and trustful method for verifying the proper functioning of future quantum networks.

published version

References in corpus (9)

• The Quantum Internet
• Entanglement detection
• An Elementary Quantum Network of Single Atoms in Optical Cavities
• Quantum Repeaters with Photon Pair Sources and Multi-Mode Memories
• Mapping photonic entanglement into and out of a quantum memory
• Experimental demonstration of a BDCZ quantum repeater node
• A computable measure of nonclassicality for light
• Field test of a continuous-variable quantum key distribution prototype
• A high-fidelity single-photon source based on a type-II optical parametric oscillator

Cited by in corpus (9)

• Optical synthesis of large-amplitude squeezed coherent-state superpositions with minimal resources
• Experimental Proof of Nonlocal Wavefunction Collapse for a Single Particle Using Homodyne Measurement
• Analog of the Clauser-Horne-Shimony-Holt inequality for steering
• Quantum state engineering by click counting
• Observing optical coherence across Fock layers with weak-field homodyne detectors
• Revealing Genuine Optical-Path Entanglement
• Single-photon quantum nonlocality: Violation of the Clauser-Horne-Shimony-Holt inequality using feasible measurement setups
• Witnessing single-photon entanglement with local homodyne measurements: analytical bounds and robustness to losses
• Divide-and-Conquer: An integrated photon-counting scheme