2,686 research outputs found
Exploring the limits of multiplexed photon-pair sources for the preparation of pure single-photon states
Current sources of heralded single photons based on nonlinear optics operate
in a probabilistic manner. In order to build quantum-enhanced devices based
around the use of single photons, compact, turn-key and deterministic sources
are required. A possible solution is to multiplex a number of sources to
increase the single-photon generation probability and in so doing reducing the
waiting time to deliver large numbers of photons simultaneously, from
independent sources. Previously it has been shown that, in the ideal case, 17
multiplexed sources allow deterministic generation of heralded single photons
[Christ and Silberhorn, Phys. Rev. A 85, 023829 (2012)]. Here we extend this
analysis to include undesirable effects of detector inefficiency and photon
loss on a number of multiplexed sources using a variety of different detectors
for heralding. We compare these systems for fixed signal-to-noise ratio to
allow a direct comparison of performance for real- world heralded single photon
sources.Comment: 10 pages, 7 figures. Equation 18 changed to include power of a half
in the binomial facto
Temporal Loop Multiplexing: A resource efficient scheme for multiplexed photon-pair sources
Single photons are a vital resource for photonic quantum information
processing. However, even state-of-the-art single photon sources based on
photon-pair generation and heralding detection have only a low probability of
delivering a single photon when one is requested. We analyse a scheme that uses
a switched fibre delay loop to increase the delivery probability per time bin
of single photons from heralded sources. We show that, for realistic
experimental parameters, combining the output of up to 15 pulses can yield a
performance improvement of a factor of 10. We consider the future performance
of this scheme with likely component improvements.Comment: 5 pages, 4 figure
Characterizing the variation of propagation constants in multicore fibre
We demonstrate a numerical technique that can evaluate the core-to-core
variations in propagation constant in multicore fibre. Using a Markov Chain
Monte Carlo process, we replicate the interference patterns of light that has
coupled between the cores during propagation. We describe the algorithm and
verify its operation by successfully reconstructing target propagation
constants in a fictional fibre. Then we carry out a reconstruction of the
propagation constants in a real fibre containing 37 single-mode cores. We find
that the range of fractional propagation constant variation across the cores is
approximately .Comment: 17 pages; preprint format; 5 figures. Submitted to Optics Expres
Passive, broadband and low-frequency suppression of laser amplitude noise to the shot-noise limit using hollow-core fibre
We use hollow-core fibre to preserve the spectrum and temporal profile of
picosecond laser pulses in CBD to suppress 2.6 dB of amplitude noise at MHz
noise frequencies, to within 0.01 dB of the shot-noise limit. We provide an
enhanced version of the CBD scheme that concatenates circuits to suppress over
multiple frequencies and over broad frequency ranges --- we perform a first
demonstration that reduces total excess amplitude noise, between 2 - 6 MHz, by
85%. These demonstrations enable passive, broad-band, all-guided fibre laser
technology operating at the shot-noise limit.Comment: 8 pages, 8 figure
A two-way photonic interface for linking Sr+ transition at 422 nm to the telecommunications C-band
We report a single-stage bi-directional interface capable of linking Sr+
trapped ion qubits in a long-distance quantum network. Our interface converts
photons between the Sr+ emission wavelength at 422 nm and the telecoms C-band
to enable low-loss transmission over optical fiber. We have achieved both up-
and down-conversion at the single photon level with efficiencies of 9.4% and
1.1% respectively. Furthermore we demonstrate noise levels that are low enough
to allow for genuine quantum operation in the future.Comment: 5 pages, 4 figure
Embodied cognitive ecosophy: the relationship of mind, body, meaning and ecology
The concept of embodied cognition has had a major impact in a number of disciplines. The extent of its consequences on general knowledge and epistemology are still being explored. Embodied cognition in human geography has its own traditions and discourses but these have become somewhat isolated in the discipline itself. This paper argues that findings in other disciplines are of value in reconceptualising embodied cognition in human geography and this is explored by reconsidering the concept of ecosophy. Criticisms of ecosophy as a theory are considered and recent work in embodied cognition is applied to consider how such criticisms might be addressed. An updated conceptualisation is proposed, the embodied cognitive ecosophy, and three characteristics arising from this criticism and synthesis are presented with a view to inform future discussions of ecosophy and emotional geography
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