101 research outputs found
High performance guided-wave asynchronous heralded single photon source
We report on a guided wave heralded photon source based on the creation of
non-degenerate photon pairs by spontaneous parametric down conversion in a
Periodically Poled Lithium Niobate waveguide. Using the signal photon at 1310
nm as a trigger, a gated detection process permits announcing the arrival of
single photons at 1550 nm at the output of a single mode optical fiber with a
high probability of 0.38. At the same time the multi-photon emission
probability is reduced by a factor of 10 compared to poissonian light sources.
Relying on guided wave technologies such as integrated optics and fiber optics
components, our source offers stability, compactness and efficiency and can
serve as a paradigm for guided wave devices applied to quantum communication
and computation using existing telecom networks
A quantum relay chip based on telecommunication integrated optics technology
We investigate an integrated optical circuit on lithium niobate designed to
implement the teleportation-based quantum relay scheme for one-way quantum
communication at a telecom wavelength. Such an advanced quantum circuit merges
for the first time, both optical-optical and electro-optical non-linear
functions necessary to implement the desired on-chip single qubit
teleportation. On one hand, spontaneous parametric down-conversion is used to
produce entangled photon-pairs. On the other hand, we take advantage of two
photon routers, consisting of electro-optically controllable couplers, to
separate the paired photons and to perform a Bell state measurement,
respectively. After having validated all the individual functions in the
classical regime, we have performed a Hong-Ou-Mandel (HOM) experiment to mimic
a one-way quantum communication link. Such a quantum effect, seen as a
prerequisite towards achieving teleportation, has been obtained, at one of the
routers, when the chip was coupled to an external single photon source. The
two-photon interference pattern shows a net visibility of 80%, which validates
the proof of principle of a "quantum relay circuit" for qubits carried by
telecom photons. In case of optimized losses, such a chip could increase the
maximal achievable distance of one-way quantum key distribution links by a
factor 1.8. Our approach and results emphasize the high potential of integrated
optics on lithium niobate as a key technology for future reconfigurable quantum
information manipulation.Comment: 16 pages, 8 figure
PPLN Waveguide for Quantum Communication
We report on energy-time and time-bin entangled photon-pair sources based on
a periodically poled lithium niobate (PPLN) waveguide. Degenerate twin photons
at 1314 nm wavelength are created by spontaneous parametric down-conversion and
coupled into standard telecom fibers. Our PPLN waveguide features a very high
conversion efficiency of about 10^(-6), roughly 4 orders of magnitude more than
that obtained employing bulk crystals. Even if using low power laser diodes,
this engenders a significant probability for creating two pairs at a time - an
important advantage for some quantum communication protocols. We point out a
simple means to characterize the pair creation probability in case of a pulsed
pump. To investigate the quality of the entangled states, we perform
photon-pair interference experiments, leading to visibilities of 97% for the
case of energy-time entanglement and of 84% for the case of time-bin
entanglement. Although the last figure must still be improved, these tests
demonstrate the high potential of PPLN waveguide based sources to become a key
element for future quantum communication schemesComment: 11 pages, 9 figures, submitted to the European Physical Journal D
(special issue of the Quick conference
Increased pump acceptance bandwidth in spontaneous parametric downconversion process using Bragg reflection waveguides
In this paper we show that by suitably tailoring the dispersion
characteristics of a Bragg reflection waveguide (BRW) mode, it is possible to
achieve efficient photon pair generation over a large pump bandwidth while
maintaining narrow signal bandwidth. The structure proposed consists of a high
index core BRW with a periodically poled GaN core and periodically stratified
cladding made up of alternate layers of and
. Such photon-pair generators should find applications in
realizing compact and stable sources for quantum information processing.Comment: 6 pages, 5 figure
Generation of polarization entangled photons using type-II doubly periodically poled lithium niobate waveguides
In this paper, we address the issue of the generation of non-degenerate
cross-polarization-entangled photon pairs using type-II periodically poled
lithium niobate. We show that, by an appropriate engineering of the
quasi-phase-matching grating, it is possible to simultaneously satisfy the
conditions for two spontaneous parametric down-conversion processes, namely
ordinary pump photon down-conversion to either extraordinary signal and
ordinary idler paired photons, or to ordinary signal and extraordinary idler
paired photons. In contrast to single type-II phase-matching, these two
processes, when enabled together, can lead to the direct production of
cross-polarization-entangled state for non degenerate signal and idler
wavelengths. Such a scheme should be of great interest in applications
requiring polarization-entangled non degenerate paired photons with, for
instance, one of the entangled photons at an appropriate wavelength being used
for local operation or for quantum storage in an atomic ensemble, and the other
one at the typical wavelength of 1550 nm for propagation through an optical
fiber.Comment: 9 pages, 5 figures, 2 table
Polarization entangled photon-pair source based on a type-II PPLN waveguide emitting at a telecom wavelength
We report the realization of a fiber coupled polarization entangled
photon-pair source at 1310 nm based on a birefringent titanium in-diffused
waveguide integrated on periodically poled lithium niobate. By taking advantage
of a dedicated and high-performance setup, we characterized the quantum
properties of the pairs by measuring two-photon interference in both
Hong-Ou-Mandel and standard Bell inequality configurations. We obtained, for
the two sets of measurements, interference net visibilities reaching nearly
100%, which represent important and competitive results compared to similar
waveguide-based configurations already reported. These results prove the
relevance of our approach as an enabling technology for long-distance quantum
communication.Comment: 13 pages, 4 figures, to appear in New Journal of Physic
Integrated optical source of polarization entangled photons at 1310 nm
We report the realization of a new polarization entangled photon-pair source
based on a titanium-indiffused waveguide integrated on periodically poled
lithium niobate pumped by a CW laser at . The paired photons are
emitted at the telecom wavelength of within a bandwidth of .
The quantum properties of the pairs are measured using a two-photon coalescence
experiment showing a visibility of 85%. The evaluated source brightness, on the
order of pairs , associated with its
compactness and reliability, demonstrates the source's high potential for
long-distance quantum communication.Comment: There is a typing mistake in the previous version in the visibility
equation. This mistake doesn't change the result
Efficacy of Infection Control Interventions in Reducing the Spread of Multidrug-Resistant Organisms in the Hospital Setting
Multidrug-resistant organisms (MDRO) continue to spread in hospitals globally, but the population-level impact of recommended preventive strategies and the relative benefit of individual strategies targeting all MDRO in the hospital setting are unclear. To explore the dynamics of MDRO transmission in the hospital, we develop a model extending data from clinical individual-level studies to quantify the impact of hand hygiene, contact precautions, reducing antimicrobial exposure and screening surveillance cultures in decreasing the prevalence of MDRO colonization and infection. The effect of an ongoing increase in the influx of patients colonized with MDRO into the hospital setting is also quantified. We find that most recommended strategies have substantial effect in decreasing the prevalence of MDRO over time. However, screening for asymptomatic MDRO colonization among patients who are not receiving antimicrobials is of minimal value in reducing the spread of MDRO
Transmission of Carbapenem-Resistant Klebsiella pneumoniae in US Hospitals
Background: Carbapenem-resistant Klebsiella pneumoniae (CRKp) is the most prevalent carbapenem-resistant Enterobacterales in the United States. We evaluated CRKp clustering in patients in US hospitals. Methods: From April 2016 to August 2017, 350 patients with clonal group 258 CRKp were enrolled in the Consortium on Resistance Against Carbapenems in Klebsiella and other Enterobacteriaceae, a prospective, multicenter, cohort study. A maximum likelihood tree was constructed using RAxML. Static clusters shared ≤21 single-nucleotide polymorphisms (SNP) and a most recent common ancestor. Dynamic clusters incorporated SNP distance, culture timing, and rates of SNP accumulation and transmission using the R program TransCluster. Results: Most patients were admitted from home (n = 150, 43%) or long-term care facilities (n = 115, 33%). Urine (n = 149, 43%) was the most common isolation site. Overall, 55 static and 47 dynamics clusters were identified involving 210 of 350 (60%) and 194 of 350 (55%) patients, respectively. Approximately half of static clusters were identical to dynamic clusters. Static clusters consisted of 33 (60%) intrasystem and 22 (40%) intersystem clusters. Dynamic clusters consisted of 32 (68%) intrasystem and 15 (32%) intersystem clusters and had fewer SNP differences than static clusters (8 vs 9; P =. 045; 95% confidence interval [CI]: -4 to 0). Dynamic intersystem clusters contained more patients than dynamic intrasystem clusters (median [interquartile range], 4 [2, 7] vs 2 [2, 2]; P =. 007; 95% CI: -3 to 0). Conclusions: Widespread intrasystem and intersystem transmission of CRKp was identified in hospitalized US patients. Use of different methods for assessing genetic similarity resulted in only minor differences in interpretation
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