27,259 research outputs found
Impurity scattering and Friedel oscillations in mono-layer black phosphorus
We study the effect of impurity scattering effect in black phosphorurene (BP)
in this work. For single impurity, we calculate impurity induced local density
of states (LDOS) in momentum space numerically based on tight-binding
Hamiltonian. In real space, we calculate LDOS and Friedel oscillation
analytically. LDOS shows strong anisotropy in BP. Many impurities in BP are
investigated using -matrix approximation when the density is low. Midgap
states appear in band gap with peaks in DOS. The peaks of midgap states are
dependent on impurity potential. For finite positive potential, the impurity
tends to bind negative charge carriers and vise versa. The infinite impurity
potential problem is related to chiral symmetry in BP
Experimental Demonstration of Quantum State Multi-meter and One-qubit Fingerprinting in a Single Quantum Device
We experimentally demonstrate in NMR a quantum interferometric multi-meter
for extracting certain properties of unknown quantum states without resource to
quantum tomography. It can perform direct state determinations,
eigenvalue/eigenvector estimations, purity tests of a quantum system, as well
as the overlap of any two unknown quantum states. Using the same device, we
also demonstrate one-qubit quantum fingerprinting
Vector magnetic field sensing by single nitrogen vacancy center in diamond
In this Letter, we proposed and experimentally demonstrated a method to
detect vector magnetic field with a single nitrogen vacancy (NV) center in
diamond. The magnetic field in parallel with the axis of the NV center can be
obtained by detecting the electron Zeeman shift, while the Larmor precession of
an ancillary nuclear spin close to the NV center can be used to measure the
field perpendicular to the axis. Experimentally, both the Zeeman shift and
Larmor precession can be measured through the fluorescence from the NV center.
By applying additional calibrated magnetic fields, complete information of the
vector magnetic field can be achieved with such a method. This vector magnetic
field detection method is insensitive to temperature fluctuation and it can be
applied to nanoscale magnetic measurement.Comment: 5 pages, 5 figure
Experimental demonstration of an efficient quantum phase-covariant cloning and its possible applications to simulating eavesdropping in quantum cryptography
We describe a nuclear magnetic resonance (NMR) experiment which implements an
efficient one-to-two qubit phase-covariant cloning machine(QPCCM). In the
experiment we have achieved remarkably high fidelities of cloning, 0.848 and
0.844 respectively for the original and the blank qubit. This experimental
value is close to the optimal theoretical value of 0.854. We have also
demonstrated how to use our phase-covariant cloning machine for quantum
simulations of bit by bit eavesdropping in the four-state quantum key
distribution protocol.Comment: 4 pages, 5 figure
Experimental Quantum Cloning with Prior Partial Information
When prior partial information about a state to be cloned is available, it
can be cloned with a fidelity higher than that of universal quantum cloning. We
experimentally verify this intriguing relationship between the cloning fidelity
and the prior information by reporting the first experimental optimal quantum
state-dependent cloning, using nuclear magnetic resonance techniques. Our
experiments may further have important implications into many quantum
information processing protocols.Comment: 4 pages, 2 figure
Novel micromachined silicon acoustic delay line systems for real-time photoacoustic tomography applications
In current photoacoustic tomography (PAT) systems, ultrasound transducer arrays and multi-channel data acquisition (DAQ) electronics are used to receive the PA signals. To achieve real-time PA imaging, massive 1D or even 2D transducer arrays and large number of DAQ channels are necessary. As a result, the ultrasound receiver becomes very complex, bulky and also costly. In this paper, we report the development of novel micromachined silicon acoustic delay line systems, which are expected to provide a new approach to address the above issue. First, fundamental building block structures of the acoustic delay line systems were designed and fabricated. Their acoustic properties were characterized with ultrasound and photoacoustic measurements. Second, two different acoustic delay line systems (parallel and serial) were designed and fabricated using advanced micromachining processes to ensure compact size, high accuracy, and good repeatability. The transmission of multiple acoustic signals in the acoustic delay line systems were studied with ultrasound experiment. Experimental results show that the silicon acoustic delay line systems can guide multiple channels of acoustic signals with low loss and distortion. With the addition of a set of suitable time delays, the time-delay acoustic signals arrived at a single-element transducer at different times and were unambiguously received and processed by the following DAQ electronics. Therefore, the micromachined silicon acoustic delay line systems could be used to combine multiple signal channels into a single one (without the involvement of electronic multiplexing), thereby reducing the complexity and cost of the ultrasound receiver for real-time PAT application
Phonon-phason coupling in icosahedral quasicrystals
From relaxation simulations of decoration-based quasicrystal structure models
using microscopically based interatomic pair potentials, we have calculated the
(usually neglected) phonon-phason coupling constant. Its sign is opposite for
the two alloys studied, i-AlMn and i-(Al,Cu)Li; a dimensionless measure of its
magnitude relative to the phonon and phason elastic constants is of order 1/10,
suggesting its effects are small but detectable. We also give a criterion for
when phonon-phason effects are noticeable in diffuse tails of Bragg peaks.Comment: 7 pages, LaTeX, uses Europhys Lett macros (included
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