Entangling independent photons by time measurement

By M. Halder, A. Beveratos, Nicolas Gisin, Valerio Scarani, C. Simon, H. Zbinden. 2007

276 citations recorded by the source corpus.

Entanglement is at the heart of quantum physics, both for its conceptual foundations and for applications in quantum communication. Remarkably, entanglement can be ‘swapped’: if we prepare two independent entangled pairs A1–A2 and B1–B2, a joint measurement on A1 and B1 (called a ‘Bell-state measurement’, BSM) has the effect of projecting A2 and B2 onto an entangled state, although these two particles have never interacted nor share any common past1,2. Entanglement swapping with photon pairs has already been experimentally demonstrated3,4,5,6 using pulsed sources—where the challenge was to achieve sufficiently sharp synchronization of the photons in the BSM—but never with continuous-wave sources, as originally proposed2. Here, we present an experiment where the coherence time of the photons exceeds the temporal resolution of the detectors. Hence, photon timing can be obtained by the detection times, and pulsed sources can be replaced by continuous-wave sources, which do not require any synchronization6,7. This allows for the first time the use of completely autonomous sources, an important step towards real-world quantum networks with truly independent and distant nodes.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/2cd555f5e7b328b8896091a6c860cbe597d93ef5

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In Atomic and Molecular Physics, and Optics

Citations in the corpus

Quantum repeaters based on atomic ensembles and linear optics (2009, background): “Whil many experimental demonstrations of entanglement swapping have been realized with entangled photons (Halder et al., 2007; Kaltenbaek et al., 2009; Pan e al., 1998; de Riedmatten et al., 2005), only one attempt has been made s far to demonstrate the swapping of entangleme t with ensemble…”
Multiphoton entanglement and interferometry (2008, background): “In such a case the pumping lasers may be cw ones.41 However, 41 A recent experiment reported by Halder et al. (2007), however, 28 such techniques are difficult to use in case of SPDC, due to lack of sufficnetly time resolving detectors.”
The security of practical quantum key distribution (2008, background): “Entangled photon pairs suitable for entanglementbased protocols or for heralded sub-Poissonian sources are mostly generated by spontaneous parametric down conversion (SPDC) (Mandel and Wolf, 1995).”
Delayed-choice gedanken experiments and their realizations (2014, unknown): “The entanglement-swapping protocol itself has been experimentally demonstrated with various physical systems (Pan et al., 1998; Barrett et al., 2004; Riebe et al., 2004; Halder et al., 2007; Matsukevich et al., 2008; Yuan et al., 2008; Kaltenbaek et al., 2009).”