4,559 research outputs found
Chip-based microcavities coupled to NV centers in single crystal diamond
Optical coupling of nitrogen vacancy centers in single-crystal diamond to an
on-chip microcavity is demonstrated. The microcavity is fabricated from a
hybrid gallium phosphide and diamond material system, and supports whispering
gallery mode resonances with spectrometer resolution limited Q > 25000
Supersymmetric quantum mechanics based on higher excited states
We generalize the formalism and the techniques of the supersymmetric (susy)
quantum mechanics to the cases where the superpotential is generated/defined by
higher excited eigenstates. The generalization is technically almost
straightforward but physically quite nontrivial since it yields an infinity of
new classes of susy-partner potentials, whose spectra are exactly identical
except for the lowest m+1 states, if the superpotential is defined in terms of
the (m+1)-st eigenfunction, with m=0 reserved for the ground state. It is shown
that in case of the infinite 1-dim potential well nothing new emerges (the
partner potential is still of P\"oschl-Teller type I, for all m), whilst in
case of the 1-dim harmonic oscillator we get a new class of infinitely many
partner potentials: for each m the partner potential is expressed as the sum of
the quadratic harmonic potential plus rational function, defined as the
derivative of the ratio of two consecutive Hermite polynomials. These partner
potentials of course have m singularities exactly at the locations of the nodes
of the generating (m+1)-st wavefunction. The susy formalism applies everywhere
between the singularities. A systematic application of the formalism to other
potentials with known spectra would yield an infinitely rich class of
"solvable" potentials, in terms of their partner potentials. If the potentials
are shape invariant they can be solved at least partially and new types of
analytically obtainable spectra are expected.
PACS numbers: 03.65.-w, 03.65.Ge, 03.65.SqComment: 15 pages LaTeX file, no figures, submitted to J. Phys. A: accepted
for publication
KIC 10449976: discovery of an extreme-helium subdwarf in the Kepler field
Optical spectroscopy of the blue star KIC 10449976 shows that it is an
extremely helium-rich subdwarf with effective temperature T=40000+/-300 K and
surface gravity log g=5.3+/-0.1. Radial-velocity measurements over a five-day
timescale show an upper variability limit of ~50+/-20 km/s. Kepler photometry
of KIC 10449976 in both long and short cadence modes shows evidence for a
periodic modulation on a timescale of ~3.9 days. We have examined the
possibility that this modulation is not astrophysical but conclude it is most
likely real. We discuss whether the modulation could be caused by a low-mass
companion, by stellar pulsations, or by spots. The identification of any one of
these as cause has important consequences for understanding the origin of
helium-rich subdwarfs.Comment: Accepted by MNRA
Properties of implanted and CVD incorporated nitrogen-vacancy centers: preferential charge state and preferential orientation
The combination of the long electron state spin coherence time and the optical coupling of the ground electronic states to an excited state manifold makes the nitrogen-vacancy (NV) center in diamond an attractive candidate for quantum information processing. To date the best spin and optical properties have been found in centers deep within the diamond crystal. For useful devices it will be necessary to engineer NVs with similar properties close to the diamond surface. We report on properties including charge state control and preferential orientation for near surface NVs formed either in CVD growth or through implantation and annealing
Observation of the dynamic Jahn-Teller effect in the excited states of nitrogen-vacancy centers in diamond
The optical transition linewidth and emission polarization of single
nitrogen-vacancy (NV) centers are measured from 5 K to room temperature.
Inter-excited state population relaxation is shown to broaden the zero-phonon
line and both the relaxation and linewidth are found to follow a T^5 dependence
for T up to 100 K. This dependence indicates that the dynamic Jahn-Teller
effect is the dominant dephasing mechanism for the NV optical transitions at
low temperatures
Low-temperature tapered-fiber probing of diamond NV ensembles coupled to GaP microcavities
In this work we present a platform for testing the device performance of a
cavity-emitter system, using an ensemble of emitters and a tapered optical
fiber. This method provides high-contrast spectra of the cavity modes,
selective detection of emitters coupled to the cavity, and an estimate of the
device performance in the single- emitter case. Using nitrogen-vacancy (NV)
centers in diamond and a GaP optical microcavity, we are able to tune the
cavity onto the NV resonance at 10 K, couple the cavity-coupled emission to a
tapered fiber, and measure the fiber-coupled NV spontaneous emission decay.
Theoretically we show that the fiber-coupled average Purcell factor is 2-3
times greater than that of free-space collection; although due to ensemble
averaging it is still a factor of 3 less than the Purcell factor of a single,
ideally placed center.Comment: 15 pages, 6 figure
Coupling of nitrogen-vacancy centers in diamond to a GaP waveguide
The optical coupling of guided modes in a GaP waveguide to nitrogen-vacancy
(NV) centers in diamond is demonstrated. The electric field penetration into
diamond and the loss of the guided mode are measured. The results indicate that
the GaP-diamond system could be useful for realizing coupled microcavity-NV
devices for quantum information processing in diamond.Comment: 4 pages 4 figure
Frequencies of Lipopolysaccharide Core Types among Clinical Isolates of Escherichia coli Defined with Monoclonal Antibodies
Mouse monoclonal antibodies (MAbs) specific for the lipopolysaccharide (LPS) core types R1, R2, and R3 of Escherichia coli and a cross-reactive MAb that binds to the LPS core of almost all E. coli were used in ELISA to determine the frequency of cores resembling R1, R2, and R3 in strains of E. coli isolated from clinical samples (blood and urine specimens) and from the feces of asymptomatic individuals. Of the 180 wild-type isolates, 123 were assigned to R1 core type, 14 to R2, and 18 to R3. Twenty-five wild-type E. coli isolates could not be assigned to a particular core type and may have either an R4 or K12 core or a previously unrecognized core type. R1 core type was associated with O types 1, 4, 6, 8, and 18 and with K1 or K5 capsules. R3 was associated with O15.O75 isolates could be of either R1 or R2 core typ
Stage-specific incidence trends of renal cancers in the East of England, 1999-2016
Objectives:
To determine stage-specific time-trends in renal cancer incidence.
Methods:
We used population-based East Anglia data 1999−2016 (population ∼2 million) on 5,456 primary renal cancer diagnoses, estimating stage-specific annual incidence using Poisson regression, allowing for changing time-trends, and adjusting for sex, age, and socioeconomic deprivation.
Results:
Renal cancer incidence increased from 9.8–16.4 cases per 100,000 during 1999−2016. Incidence of Stage I, II, and III cases increased over time, most steeply for Stage I, with annual Incidence Rate Ratio [IRR] for Stage I of 1.09 (95 % CI 1.07–1.12) during 1999−2010; and 1.03 (1.00–1.05) during 2011−2016. In contrast, the annual incidence of Stage IV renal cancer decreased during most years, IRR of 0.99 (0.98–1.00) during 2003−2016.
Conclusion:
The findings are consistent with both earlier detection of symptomatic renal cancer and increasing identification of asymptomatic lesions. However, the decreasing incidence of late-stage disease suggests genuine shifts towards earlier diagnosis
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