22 research outputs found
Remote state preparation of a photonic quantum state via quantum teleportation
We demonstrate an experimental realization of remote state preparation via
the quantum teleportation algorithm, using an entangled photon pair in the
polarization degree of freedom as the quantum resource. The input state is
encoded on the path of one of the photons from the pair. The improved
experimental scheme allows us to control the preparation and teleportation of a
state over the entire Bloch sphere with a resolution of the degree of mixture
given by the coherence length of the photon pair. Both the preparation of the
input state and the implementation of the quantum gates are performed in a pair
of chained displaced Sagnac interferometers, which contribute to the overall
robustness of the setup. An average fidelity above 0.9 is obtained for the
remote state preparation process. This scheme allows for a prepared state to be
transmitted on every repetition of the experiment, thus giving an intrinsic
success probability of 1.Comment: 6 pages, 4 figures, accepted for publication in Applied Physics
B:Lasers and Optic
Noisy quantum teleportation: An experimental study on the influence of local environments
We report experimental results on the action of selected local environments
on the fidelity of the quantum teleportation protocol, taking into account
non-ideal, realistic entangled resources. Different working conditions are
theoretically identified, where a noisy protocol can be made almost insensitive
to further addition of noise. We put to test these conditions on a photonic
implementation of the quantum teleportation algorithm, where two polarization
entangled qubits act as the entangled resource and a path qubit on Alice
encodes the state to be teleported. Bob's path qubit is used to implement a
local environment, while the environment on Alice's qubit is simulated as a
weighed average of different pure states. We obtain a good agreement with the
theoretical predictions, we experimentally recreate the conditions to obtain a
noise-induced enhancement of the protocol fidelity, and we identify parameter
regions of increased insensibility to interactions with specific noisy
environments.Comment: 9 pages, 7 figures, accepted for publication in Phys. Rev.
Entanglement breaking channels and entanglement sudden death
The occurrence of entanglement sudden death in the evolution of a bipartite
system depends on both the initial state and the channel responsible for the
evolution. An extreme case is that of entanglement braking channels, which are
channels that acting on only one of the subsystems drives them to full
disentanglement regardless of the initial state. In general, one can find
certain combinations of initial states and channels acting on one or both
subsystems that can result in entanglement sudden death or not. Neither the
channel nor the initial state, but their combination, is responsible for this
effect, but their combination. In this work we show that, in all cases, when
entanglement sudden death occurs, the evolution can be mapped to that of an
effective entanglement breaking channel on a modified initial state. Our
results allow to anticipate which states will suffer entanglement sudden death
or not for a given evolution. An experiment with polarization entangled photons
demonstrates the utility of this result in a variety of cases
Scheme for sub-shot-noise transmission measurement using a time multiplexed single-photon source
A promising result from optical quantum metrology is the ability to achieve
sub-shot-noise performance in transmission or absorption measurements. This is
due to the significantly lower uncertainty in light intensity of quantum beams
with respect to their classical counterparts. In this work, we simulate the
outcome of an experiment that uses a multiplexed single-photon source based on
pair generation by continuous spontaneous parametric down conversion (SPDC)
followed by a time multiplexing set-up with a binary temporal division
strategy, considering several types of experimental losses. With such source,
the sub-Poissonian statistics of the output signal is the key for achieving
sub-shot-noise performance. We compare the numerical results with two
paradigmatic limits: the shot-noise limit (achieved using coherent sources) and
the quantum limit (obtained with an ideal photon-number Fock state as the input
source). We also investigate conditions in which threshold detectors can be
used, and the effect of input light fluctuations on the measurement error.
Results show that sub-shot-noise performance can be achieved, even without
using number-resolving detectors, with improvement factors that range from 1.5
to 2. This technique would allow measurements of optical absorption of a sample
with reasonable uncertainty using ultra-low light intensity and minimum
disruption of biological or other fragile specimens.Comment: 10 pages, 8 figure
Optical transmitter for time-bin encoding Quantum Key Distribution
We introduce an electro-optical arrangement that is able to produce time-bin
encoded symbols with the decoy state method over a standard optical fiber in
the C-band telecom window. The device consists of a specifically designed pulse
pattern generator for pulse production, a field-programmable gate array that
controls timing and synchronization. The electrical pulse output drive a
sequence of intensity modulators acting on a continuous laser that deliver
bursts of weak optical pulse pairs of discrete intensity values. Such
transmitter allows for the generation of all the quantum states needed to
implement a discrete variable Quantum Key Distribution protocol over a
single-mode fiber channel. Symbols are structured in bursts; the minimum
relative delay between pulses is 1.25 ns, and the maximum symbol rate within a
burst is 200 MHz. We test the transmitter on simulated optical channels of 7dB
and 14dB loss, obtaining maximum extractable secure key rates of 3.0 kb/s and
0.57 kb/s respectively. Time bin state parameters such as symbol rate, pulse
separation and intensity ratio between signal and decoy states can be easily
accessed and changed, allowing the transmitter to adapt to different
experimental conditions and contributing to standardization of QKD
implementations.Comment: 8 pages, 4 figure
Autonomous open-source hardware apparatus for quantum key distribution
We describe an autonomous, fully functional implementation of the BB84 quantum key distribution protocol using open source hardware microcontrollers for the synchronization, communication, key sifting and real-time key generation diagnostics. The quantum bits are prepared in the polarization of weak optical pulses generated with light emitting diodes, and detected using a sole single-photon counter and a temporally multiplexed scheme. The system generates a shared cryptographic key at a rate of 365 bps, with a raw quantum bit error rate of 2.7%. A detailed description of the peripheral electronics for control, driving and communication between stages is released as supplementary material. The device can be built using simple and reliable hardware and it is presented as an alternative for a practical realization of sophisticated, yet accessible quantum key distribution systems.
Received: 11 Novembre 2015, Accepted: 7 January 2016; Edited by: O. Martínez; DOI: http://dx.doi.org/10.4279/PIP.080002
Cite as: I H López Grande, C T Schmiegelow, M A Larotonda, Papers in Physics 8, 080002 (2016
Photon counting module based on avalanche photodiodes
Se presenta el desarrollo y las características de un módulo de conteo de fotones basado en un fotodiodo de avalancha. La versión final del mismo está construida a partir de un fotodiodo Excelitas C30902SH-DTC, el cual dispone de un sistema de enfriamiento basado en celdas termoeléctricas. El circuito de quenching activo del mismo está construido a partir de electrónica discreta de alta velocidad. El módulo dispone de un acople a fibra óptica estándar FC que permite acoplar el detector a fibras multi o monomodo. Asimismo se caracterizó la tasa máxima de detecciones en alrededor de 500k c/s, una eficiencia de detección comparable a la de un módulo comercial, una tasa de cuentas de oscuridad de alrededor de 1500 c/s, y una probabilidad de afterpulsing del orden del 6%.We report the development and characterization of a photon counting module based on an avalanche photodiode. The device uses an Excelitas C30902SH-DTC silicon avalanche photodiode as the detector, which has a built-in thermoelectric cooler. It includes a high speed active quenching circuit built using fast discrete integrated circuits. The device also includes a standard FC optical fiber connector, that allows to couple the detector to single or multi mode fibers. The maximum achievable count rate achievable is around 500k c/s, with a dark count rate of 1500 c/s and an afterpulsing probability of around 6%. These characteristics were obtained at a detection efficiency comparable to a commercial photon counting module.Fil: Bordakevich, Sebastian Andres. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Kielbowicz, A. A.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: López Grande, Ignacio Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Larotonda, Miguel Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Centro de Investigación en Láseres y Aplicaciones; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentin