57 research outputs found
A source of polarization-entangled photon pairs interfacing quantum memories with telecom photons
We present a source of polarization-entangled photon pairs suitable for the
implementation of long-distance quantum communication protocols using quantum
memories. Photon pairs with wavelengths 883 nm and 1338 nm are produced by
coherently pumping two periodically poled nonlinear waveguides embedded in the
arms of a polarization interferometer. Subsequent spectral filtering reduces
the bandwidth of the photons to 240 MHz. The bandwidth is well-matched to a
quantum memory based on an Nd:YSO crystal, to which, in addition, the center
frequency of the 883 nm photons is actively stabilized. A theoretical model
that includes the effect of the filtering is presented and accurately fits the
measured correlation functions of the generated photons. The model can also be
used as a way to properly assess the properties of the source. The quality of
the entanglement is revealed by a visibility of V = 96.1(9)% in a Bell-type
experiment and through the violation of a Bell inequality.Comment: 15 pages, 8 figures, 3 table
Waveguide-based OPO source of entangled photon pairs
In this paper we present a compact source of narrow-band energy-time
entangled photon pairs in the telecom regime based on a Ti-indiffused
Periodically Poled Lithium Niobate (PPLN) waveguide resonator, i.e. a waveguide
with end-face dielectric multi-layer mirrors. This is a monolithic doubly
resonant Optical Parametric Oscillator (OPO) far below threshold, which
generates photon pairs by Spontaneous Parametric Down Conversion (SPDC) at
around 1560nm with a 117MHz (0.91 pm)- bandwidth. A coherence time of 2.7 ns is
estimated by a time correlation measurement and a high quality of the entangled
states is confirmed by a Bell-type experiment. Since highly coherent
energy-time entangled photon pairs in the telecom regime are suitable for long
distance transmission and manipulation, this source is well suited to the
requirements of quantum communication.Comment: 13 page
Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory
In quantum teleportation, the state of a single quantum system is disembodied
into classical information and purely quantum correlations, to be later
reconstructed onto a second system that has never directly interacted with the
first one. This counterintuitive phenomenon is a cornerstone of quantum
information science due to its essential role in several important tasks such
as the long-distance transmission of quantum information using quantum
repeaters. In this context, a challenge of paramount importance is the
distribution of entanglement between remote nodes, and to use this entanglement
as a resource for long-distance light-to-matter quantum teleportation. Here we
demonstrate quantum teleportation of the polarization state of a
telecom-wavelength photon onto the state of a solid-state quantum memory.
Entanglement is established between a rare-earth-ion doped crystal storing a
single photon that is polarization-entangled with a flying telecom-wavelength
photon. The latter is jointly measured with another flying qubit carrying the
polarization state to be teleported, which heralds the teleportation. The
fidelity of the polarization state of the photon retrieved from the memory is
shown to be greater than the maximum fidelity achievable without entanglement,
even when the combined distances travelled by the two flying qubits is 25 km of
standard optical fibre. This light-to-matter teleportation channel paves the
way towards long-distance implementations of quantum networks with solid-state
quantum memories.Comment: 5 pages (main text) + appendix (10 pages
Conditional detection of pure quantum states of light after storage in a waveguide
Conditional detection is an important tool to extract weak signals from a
noisy background and is closely linked to heralding, which is an essential
component of protocols for long distance quantum communication and distributed
quantum information processing in quantum networks. Here we demonstrate the
conditional detection of time-bin qubits after storage in and retrieval from a
photon-echo based waveguide quantum memory. Each qubit is encoded into one
member of a photon-pair produced via spontaneous parametric down conversion,
and the conditioning is achieved by the detection of the other member of the
pair. Performing projection measurements with the stored and retrieved photons
onto different bases we obtain an average storage fidelity of 0.885 \pm 0.020,
which exceeds the relevant classical bounds and shows the suitability of our
integrated light-matter interface for future applications of quantum
information processing.Comment: 4 pages, 4 figure
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