65 research outputs found
Experimental wavelength division multiplexed photon pair distribution
We have experimentally implemented the distribution of photon pairs produced
by spontaneous parametric down conversion through telecom dense wavelength
division multiplexing filters. Using the measured counts and coincidences
between symmetric channels, we evaluate the maximum fringe visibility that can
be obtained with polarization entangled photons and compare different filter
technologies.Comment: 3 pages, 4 figures, submitted to Optics Letter
Experimental detection of steerability in Bell local states with two measurement settings
Steering, a quantum property stronger than entanglement but weaker than
non-locality in the quantum correlation hierarchy, is a key resource for
one-sided device-independent quantum key distribution applications, in which
only one of the communicating parties is trusted. A fine-grained steering
inequality was introduced in [PRA 90 050305(R) (2014)], enabling for the first
time the detection of steering in all steerable two-qubit Werner states using
only two measurement settings. Here we numerically and experimentally
investigate this inequality for generalized Werner states and successfully
detect steerability in a wide range of two-photon polarization-entangled Bell
local states generated by a parametric down-conversion source.Comment: 9 pages, 7 figures (including Appendix
Band-edge-induced Bragg diffraction in two-dimensional photonic crystals
Two-dimensional photonic crystals composed of two orthogonal volume diffraction gratings have been photogenerated in photopolymers. When the read beam is set at the Bragg angle, the diffraction efficiency of the transmission grating is strongly enhanced at the band edge of the reflection grating recorded in the material. Such a device provides Bragg operation and enhancement of the diffraction efficiency of the thin diffraction grating together with good wavelength selectivity. Such advantages could be interesting for optical
signal processing
Experimental investigation of practical unforgeable quantum money
Wiesner's unforgeable quantum money scheme is widely celebrated as the first
quantum information application. Based on the no-cloning property of quantum
mechanics, this scheme allows for the creation of credit cards used in
authenticated transactions offering security guarantees impossible to achieve
by classical means. However, despite its central role in quantum cryptography,
its experimental implementation has remained elusive because of the lack of
quantum memories and of practical verification techniques. Here, we
experimentally implement a quantum money protocol relying on classical
verification that rigorously satisfies the security condition for
unforgeability. Our system exploits polarization encoding of weak coherent
states of light and operates under conditions that ensure compatibility with
state-of-the-art quantum memories. We derive working regimes for our system
using a security analysis taking into account all practical imperfections. Our
results constitute a major step towards a real-world realization of this
milestone protocol.Comment: 10 pages, 5 figure
Simple performance evaluation of pulsed spontaneous parametric down-conversion sources for quantum communications
Fast and complete characterization of pulsed spontaneous parametric down
conversion (SPDC) sources is important for applications in quantum information
processing and communications. We propose a simple method to perform this task,
which only requires measuring the counts on the two output channels and the
coincidences between them, as well as modeling the filter used to reduce the
source bandwidth. The proposed method is experimentally tested and used for a
complete evaluation of SPDC sources (pair emission probability, total losses,
and fidelity) of different bandwidths. This method can find applications in the
setting up of SPDC sources and in the continuous verification of the quality of
quantum communication links
Parallelizable Synthesis of Arbitrary Single-Qubit Gates with Linear Optics and Time-Frequency Encoding
We propose novel methods for the exact synthesis of single-qubit unitaries
with high success probability and gate fidelity, considering both time-bin and
frequency-bin encodings. The proposed schemes are experimentally implementable
with a spectral linear-optical quantum computation (S- LOQC) platform, composed
of electro-optic phase modulators and phase-only programmable filters (pulse
shapers). We assess the performances in terms of fidelity and probability of
the two simplest 3-components configurations for arbitrary gate generation in
both encodings and give an exact analytical solution for the synthesis of an
arbitrary single-qubit unitary in the time-bin encoding, using a single-tone
Radio Frequency (RF) driving of the EOMs. We further investigate the
parallelization of arbitrary single-qubit gates over multiple qubits with a
compact experimental setup, both for spectral and temporal encodings. We
systematically evaluate and discuss the impact of the RF bandwidth - that
conditions the number of tones driving the modulators - and of the choice of
encoding for different targeted gates. We moreover quantify the number of high
fidelity Hadamard gates that can be synthesized in parallel, with minimal and
increasing resources in terms of driving RF tones in a realistic system. Our
analysis positions spectral S-LOQC as a promising platform to conduct massively
parallel single qubit operations, with potential applications to quantum
metrology and quantum tomography.Comment: 21 pages, 6 figure
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