49 research outputs found
Witnessing single-photon entanglement with local homodyne measurements: analytical bounds and robustness to losses
Single-photon entanglement is one of the primary resources for quantum
networks, including quantum repeater architectures. Such entanglement can be
revealed with only local homodyne measurements through the entanglement witness
presented in [Morin et al. Phys. Rev. Lett. 110, 130401 (2013)]. Here, we
provide an extended analysis of this witness by introducing analytical bounds
and by reporting measurements confirming its great robustness with regard to
losses. This study highlights the potential of optical hybrid methods, where
discrete entanglement is characterized through continuous-variable
measurements
Effect of the heralding detector properties on the conditional generation of single-photon states
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. After reviewing the theoretical description of optical detectors and conditional measurements, and how both are here connected, 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
Experimental investigation of amplitude and phase quantum correlations in a type II OPO above threshold: from the non-degenerate to the degenerate operation
We describe a very stable type II optical parametric oscillator operated
above threshold which provides 9.7 0.5 dB (89%) of quantum noise
reduction on the intensity difference of the signal and idler modes. We also
report the first experimental study by homodyne detection of the generated
bright two-mode state in the case of frequency degenerate operation obtained by
introducing a birefringent plate inside the optical cavity
Mapping entanglement in and out of quantum memories
We report entanglement generation in atomic quantum memories via deterministic mapping of photonic entanglement. The atomic entanglement is retrieved back into photon modes after a programmable storage time, with an overall efficiency of 17%
Compact Source of EPR Entanglement and Squeezing at Very Low Noise Frequencies
We report on the experimental demonstration of strong quadrature EPR entanglement and squeezing at very low noise sideband frequencies produced by a single type-II, self-phase-locked, frequency degenerate optical parametric oscillator below threshold. The generated two-mode squeezed vacuum state is preserved for noise frequencies as low as 50 kHz. Designing simple setups able to generate non-classical states of light in the kHz regime is a key challenge for high sensitivity detection of ultra-weak physical effects such as gravitational wave or small beam displacement
Witnessing trustworthy single-photon entanglement with local homodyne measurements
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.Comment: published versio
Matter-matter entanglement for quantum networks
Developments in quantum information science rely critically on entanglement, as its distribution between different parties enables quantum communication protocols, such as quantum key distribution or teleportation. This talk focused on two different ways to generate heralded entanglement between matter systems, a critical requirement for scalable quantum networking