117 research outputs found
Depletion of nitrogen-vacancy color centers in diamond via hydrogen passivation
We show a marked reduction in the emission from nitrogen-vacancy (NV) color
centers in single crystal diamond due to exposure of the diamond to hydrogen
plasmas ranging from 700{\deg}C to 1000{\deg}C. Significant fluorescence
reduction was observed beneath the exposed surface to at least 80mm depth after
~10 minutes, and did not recover after post-annealing in vacuum for seven hours
at 1100{\deg}C. We attribute the fluorescence reduction to the formation of NVH
centers by the plasma induced diffusion of hydrogen. These results have
important implications for the formation of nitrogen-vacancy centers for
quantum applications, and inform our understanding of the conversion of
nitrogen-vacancy to NVH, whilst also providing the first experimental evidence
of long range hydrogen diffusion through intrinsic high-purity diamond
material.Comment: 6 pages, 3 figure
Deterministic optical quantum computer using photonic modules
The optical quantum computer is one of the few experimental systems to have
demonstrated small scale quantum information processing. Making use of cavity
quantum electrodynamics approaches to operator measurements, we detail an
optical network for the deterministic preparation of arbitrarily large
two-dimensional cluster states. We show that this network can form the basis of
a large scale deterministic optical quantum computer that can be fabricated
entirely on chip.Comment: 9 pages, 10 figures, minor revision
Resonant enhancement of the zero-phonon emission from a color center in a diamond cavity
We demonstrate coupling of the zero-phonon line of individual
nitrogen-vacancy centers and the modes of microring resonators fabricated in
single-crystal diamond. A zero-phonon line enhancement exceeding ten-fold is
estimated from lifetime measurements at cryogenic temperatures. The devices are
fabricated using standard semiconductor techniques and off-the-shelf materials,
thus enabling integrated diamond photonics.Comment: 5 pages, 4 figure
Slot-waveguide cavities for optical quantum information applications
To take existing quantum optical experiments and devices into more practical
regimes requires the construction of robust, solid-state implementations. In
particular, to observe the strong-coupling regime of atom-photon interactions
requires very small cavities and large quality factors. Here we show that the
slot-waveguide geometry recently introduced for photonic applications is also
promising for quantum optical applications in the visible regime. We study
diamond- and GaP-based slot-waveguide cavities (SWCs) compatible with diamond
colour centres e.g. nitrogen-vacancy (NV) defect, and show that one can achieve
increased single-photon Rabi frequencies of order O(10^11) Hz in ultra-small
cavity modal volumes, nearly 2 orders of magnitude smaller than previously
studied diamond-based photonic crystal cavities.Comment: 9 pages, 4 figures (all in colour), minor revision
Stimulation by voluntary exercise of adrenal glucocorticoid secretion in mature female hamsters
The possibility that habitual voluntary running induces a chronic change in adrenal glucocorticoid synthesis and secretion was examined in freely running mature female hamsters, in whom this behavior accelerates growth, reduces body fat levels, and elevates core temperature. Hamsters were free to run on horizontal discs or in vertical wheels between 32 and 80 days, in 14L:10D or in 10L:14D photoperiods, and at the end of this period, corticosterone and cortisol steroidogenesis and serial plasma corticosterone concentrations during day and night were used as measures of the chronic stimulation of adrenal cortical activity. Habitual voluntary running significantly increased steroidogenesis of both glucocorticoids and plasma corticosterone concentrations and alone accounted for all the variance in enhanced synthesis and secretion of corticosterone. Acute exercise and/or the nocturnal phase of circadian period enhanced the chronic stimulatory effects of exercise on cortiol. Despite its voluntary and apparently stress-free nature, running induces chronic increases in basal glucocorticoid secretion in mature female hamsters. Putative oversecretion of corticotropin releasing factor in freely running hamsters could account for increased steriodogenesis, acceleration of growth, reduced body fat levels, and core temperature elevation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30139/1/0000516.pd
Quantum phase transitions of light
Recently, condensed matter and atomic experiments have reached a length-scale
and temperature regime where new quantum collective phenomena emerge. Finding
such physics in systems of photons, however, is problematic, as photons
typically do not interact with each other and can be created or destroyed at
will. Here, we introduce a physical system of photons that exhibits strongly
correlated dynamics on a meso-scale. By adding photons to a two-dimensional
array of coupled optical cavities each containing a single two-level atom in
the photon-blockade regime, we form dressed states, or polaritons, that are
both long-lived and strongly interacting. Our zero temperature results predict
that this photonic system will undergo a characteristic Mott insulator
(excitations localised on each site) to superfluid (excitations delocalised
across the lattice) quantum phase transition. Each cavity's impressive photon
out-coupling potential may lead to actual devices based on these quantum
many-body effects, as well as observable, tunable quantum simulators. We
explicitly show that such phenomena may be observable in micro-machined diamond
containing nitrogen-vacancy colour centres and superconducting microwave
strip-line resonators.Comment: 11 pages, 5 figures (2 in colour
Liquid-infiltrated photonic crystals - enhanced light-matter interactions for lab-on-a-chip applications
Optical techniques are finding widespread use in analytical chemistry for
chemical and bio-chemical analysis. During the past decade, there has been an
increasing emphasis on miniaturization of chemical analysis systems and
naturally this has stimulated a large effort in integrating microfluidics and
optics in lab-on-a-chip microsystems. This development is partly defining the
emerging field of optofluidics. Scaling analysis and experiments have
demonstrated the advantage of micro-scale devices over their macroscopic
counterparts for a number of chemical applications. However, from an optical
point of view, miniaturized devices suffer dramatically from the reduced
optical path compared to macroscale experiments, e.g. in a cuvette. Obviously,
the reduced optical path complicates the application of optical techniques in
lab-on-a-chip systems. In this paper we theoretically discuss how a strongly
dispersive photonic crystal environment may be used to enhance the light-matter
interactions, thus potentially compensating for the reduced optical path in
lab-on-a-chip systems. Combining electromagnetic perturbation theory with
full-wave electromagnetic simulations we address the prospects for achieving
slow-light enhancement of Beer-Lambert-Bouguer absorption, photonic band-gap
based refractometry, and high-Q cavity sensing.Comment: Invited paper accepted for the "Optofluidics" special issue to appear
in Microfluidics and Nanofluidics (ed. Prof. David Erickson). 11 pages
including 8 figure
One- and two-dimensional photonic crystal micro-cavities in single crystal diamond
The development of solid-state photonic quantum technologies is of great
interest for fundamental studies of light-matter interactions and quantum
information science. Diamond has turned out to be an attractive material for
integrated quantum information processing due to the extraordinary properties
of its colour centres enabling e.g. bright single photon emission and spin
quantum bits. To control emitted photons and to interconnect distant quantum
bits, micro-cavities directly fabricated in the diamond material are desired.
However, the production of photonic devices in high-quality diamond has been a
challenge so far. Here we present a method to fabricate one- and
two-dimensional photonic crystal micro-cavities in single-crystal diamond,
yielding quality factors up to 700. Using a post-processing etching technique,
we tune the cavity modes into resonance with the zero phonon line of an
ensemble of silicon-vacancy centres and measure an intensity enhancement by a
factor of 2.8. The controlled coupling to small mode volume photonic crystal
cavities paves the way to larger scale photonic quantum devices based on
single-crystal diamond
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