Génération d’états non gaussiens et effets de la mesure
Kun Huang, Jianli Liu, Olivier Morin, Claude Fabre and Julien Laurat
Single-photons play an important role in emerging quantum technologies and information processing. An efficient generation technique consists in preparing such states via a conditional measurement on photon-number correlated beams : the detection of a single-photon on one of the beam can herald the generation of a single-photon state on the other one. Such scheme strongly depends on the heralding detector properties, such as its quantum efficiency, noise or photon-number resolution ability. These parameters affect the preparation rate and the fidelity of the generated state. We evaluate the effects of these properties and compare two kind of devices, a conventional on/off detector and a two-channel detector with photon-number resolution ability.
Using a continuous-wave type-II optical parametric oscillator below threshold, we have demonstrated a novel source of heralded single-photons with high fidelity. The generated state is characterized by homodyne detection and exhibits a 75% fidelity with a single-photon Fock state (91% after correction of detection loss). The low admixture of vacuum and the perfect spatiotemporal mode are critical requirements for their subsequent use in quantum information processing.
We also recently demonstrated a hybrid protocol for witnessing single-photon entanglement. Such entanglement constitutes the simplest form of entanglement. Yet it provides a valuable resource in quantum information science. It lies at the heart of quantum networks, as it can be used for quantum teleportation, swapped and purified with linear optics. The main drawback of such entanglement is the difficulty in measuring it. Our novel operational witness uses local homodyne measurements and does not rely on assumptions on the Hilbert space dimension or post-selection. This result highlights the potential of hybrid methods, where discrete entanglement is efficiently characterized via continuous-variable measurements.
Recent papers :
O. Morin, J-D. Bancal, M. Ho, P. Sekatski, V. D’Auria, N. Gisin, J. Laurat, N. Sangouard, « Witnessing single-photon entanglement with local homodyne measurements”, ArXiv
O. Morin, V. D’Auria, C. Fabre, J. Laurat, « High-fidelity single-photon source based on a Type II optical parametric oscillator” Optics Lett. 37, 3738 (2012)
V. D’Auria, O. Morin, C. Fabre, J. Laurat, « Effect of the heralding detector properties on the generation of single-photon states” Eur. Jour. Phys. D 66, 249 (2012)
with a special highlight from EPJ : HiFi Single photons
T. Amri, J. Laurat, C. Fabre « Characterizing Quantum Properties of a measurement apparatus : insights from the retrodictive approach” Phys. Rev. Letters 106, 020502 (2011)
V. D’Auria, N. Lee, T. Amri, C. Fabre, J. Laurat “Quantum Decoherence of Single-Photon Counters” Phys. Rev. Letters 107, 050504 (2011)