17,383 research outputs found
Cavity-Enhanced Two-Photon Interference using Remote Quantum Dot Sources
Quantum dots in cavities have been shown to be very bright sources of
indistinguishable single photons. Yet the quantum interference between two
bright quantum dot sources, a critical step for photon based quantum
computation, has never been investigated. Here we report on such a measurement,
taking advantage of a deterministic fabrication of the devices. We show that
cavity quantum electrodynamics can efficiently improve the quantum interference
between remote quantum dot sources: poorly indistinguishable photons can still
interfere with good contrast with high quality photons emitted by a source in
the strong Purcell regime. Our measurements and calculations show that cavity
quantum electrodynamics is a powerful tool for interconnecting several devices.Comment: 5 pages, 4 figures (Supp. Mat. attached
An audio FIR-DAC in a BCD process for high power Class-D amplifiers
A 322 coefficient semi-digital FIR-DAC using a 1-bit PWM input signal was designed and implemented in a high voltage, audio power bipolar CMOS DMOS (BCD) process. This facilitates digital input signals for an analog class-D amplifier in BCD. The FIR-DAC performance depends on the ISI-resistant nature of this PWM-signal. An impulse response with only positive coefficients was chosen, because of its resistance to deadzone and mismatch. With a DAC current of 0.5 mA, the dynamic range is 111 dB (A-weighted), with SINAD = 103 dB (A-weighted). The current consumption is 1mA for the analog part and 4.8 mA for the digital part. The power consumption is 29 mW at V/sub dd/ = 5 V and the chip area is 2 mm/sup 2/ including the reference diode that can be shared by more channels
X-ray magnetic circular dichroism in (Ge,Mn) compounds: experiments and modeling
X-ray absorption (XAS) and x-ray magnetic circular dichroism (XMCD) spectra
at the L edges of Mn in (Ge,Mn) compounds have been measured and are
compared to the results of first principles calculation. Early \textit{ab
initio} studies show that the Density Functional Theory (DFT) can very well
describe the valence band electronic properties but fails to reproduce a
characteristic change of sign in the L XMCD spectrum of Mn in
GeMn, which is observed in experiments. In this work we demonstrate
that this disagreement is partially related to an underestimation of the
exchange splitting of Mn 2 core states within the local density
approximation. It is shown that the change in sign experimentally observed is
reproduced if the exchange splitting is accurately calculated within the
Hartree-Fock approximation, while the final states can be still described by
the DFT. This approach is further used to calculate the XMCD in different
(Ge,Mn) compounds. It demonstrates that the agreement between experimental and
theoretical spectra can be improved by combining state of the art calculations
for the core and valence states respectively.Comment: 8 page
Evidence for Coexistence of Bulk Superconductivity and Itinerant Antiferromagnetism in the Heavy Fermion System CeCo(InCd)
In the generic phase diagram of heavy fermion systems, tuning an external
parameter such as hydrostatic or chemical pressure modifies the superconducting
transition temperature. The superconducting phase forms a dome in the
temperature-tuning parameter phase diagram, which is associated with a maximum
of the superconducting pairing interaction. Proximity to antiferromagnetism
suggests a relation between the disappearance of antiferromagnetic order and
superconductivity. We combine muon spin rotation, neutron scattering, and x-ray
absorption spectroscopy techniques to gain access to the magnetic and
electronic structure of CeCo(InCd) at different time scales.
Different magnetic structures are obtained that indicate a magnetic order of
itinerant character, coexisting with bulk superconductivity. The suppression of
the antiferromagnetic order appears to be driven by a modification of the
bandwidth/carrier concentration, implying that the electronic structure and
consequently the interplay of superconductivity and magnetism is strongly
affected by hydrostatic and chemical pressure.Comment: Article + Supplementary information 33 pages, 13 figure
Universal magnetic structure of the half-magnetization phase in Cr-based spinels
Using an elastic neutron scattering technique under a pulsed magnetic field
up to 30 T, we determined the magnetic structure in the half-magnetization
plateau phase in the spinel CdCrO. The magnetic structure has a cubic
32 symmetry, which is the same as that observed in HgCrO. This
suggests that there is a universal field induced spin-lattice coupling
mechanism at work in the Cr-based spinels.Comment: 4 pages, 4 figure
MIMAC: MIcro-tpc MAtrix of Chambers for dark matter directional detection
Directional detection of non-baryonic Dark Matter is a promising search
strategy for discriminating WIMP events from neutrons, the ultimate background
for dark matter direct detection. This strategy requires both a precise
measurement of the energy down to a few keV and 3D reconstruction of tracks
down to a few mm. The MIMAC (MIcro-tpc MAtrix of Chambers) collaboration has
developed in the last years an original prototype detector based on the direct
coupling of large pixelized micromegas with a special developed fast
self-triggered electronics showing the feasibility of a new generation of
directional detectors. The first bi-chamber prototype has been installed at
Modane, underground laboratory in June 2012. The first undergournd background
events, the gain stability and calibration are shown. The first spectrum of
nuclear recoils showing 3D tracks coming from the radon progeny is presented.Comment: Proceedings of the 4th International Conference on Directional Dark
Matter Detection CYGNUS2013, held in Toyoma (Japan), June 201
Polygons vs. clumps of discs: a numerical study of the influence of grain shape on the mechanical behaviour of granular materials
We performed a series of numerical vertical compression tests on assemblies
of 2D granular material using a Discrete Element code and studied the results
with regard to the grain shape. The samples consist of 5,000 grains made from
either 3 overlapping discs (clumps - grains with concavities) or six-edged
polygons (convex grains). These two grain type have similar external envelopes,
which is a function of a geometrical parameter .
In this paper, the numerical procedure applied is briefly presented followed
by the description of the granular model used. Observations and mechanical
analysis of dense and loose granular assemblies under isotropic loading are
made. The mechanical response of our numerical granular samples is studied in
the framework of the classical vertical compression test with constant lateral
stress (biaxial test). The comparison of macroscopic responses of dense and
loose samples with various grain shapes shows that when is considered
a concavity parameter, it is therefore a relevant variable for increasing
mechanical performances of dense samples. When is considered an
envelope deviation from perfect sphericity, it can control mechanical
performances for large strains. Finally, we present some remarks concerning the
kinematics of the deformed samples: while some polygon samples subjected to a
vertical compression present large damage zones (any polygon shape), dense
samples made of clumps always exhibit thin reflecting shear bands. This paper
was written as part of a CEGEO research project www.granuloscience.comComment: This version of the paper doesn't include figures. Visit the journal
web site to download the final version of the paper with the figure
Temperature and Magnetic Field Dependencies of Condon Domain Phase in Lifschitz-Kosevich-Shoenberg Approximation
The temperature and magnetic field behavior of non-uniform diamagnetic phase
of strongly correlated electron gas at the conditions of dHvA effect is
analyzed. It is shown, that in the framework of Lifschitz-Kosevich-Shoenberg
approximation the magnetic induction splitting, as well as the range of
existence of Condon domains, are characterized by strong dependencies on
temperature, magnetic field and impurities of the sample.Comment: 7 pages, 7 figure
- …