9,024 research outputs found
Noise-Free Measurement of Harmonic Oscillators with Instantaneous Interactions
We present a method of measuring the quantum state of a harmonic oscillator
through instantaneous probe-system selective interactions of the
Jaynes-Cummings type. We prove that this scheme is robust to general
decoherence mechanisms, allowing the possibility of measuring fast-decaying
systems in the weak-coupling regime. This method could be applied to different
setups: motional states of trapped ions, microwave fields in cavity/circuit
QED, and even intra-cavity optical fields.Comment: 4 pages, no figure, published in Physical Review Letter
Comment on "Topological stability of the half-vortices in spinor exciton-polariton condensates"
We show that recent paper by Flayac et al. [Phys. Rev. B 81, 045318 (2010)
and arXiv:0911.1650] is misleading. We demonstrate the existence of static
half-quantum vortices in exciton-polariton condensates and calculate the
warping of their polarization texture produced by TE-TM splitting of polariton
band.Comment: 4 pages, 1 figure. More material was added (in particular, on the
current flow)
Vortices in exciton-polariton condensates with polarization splitting
The presence of polarization splitting of exciton-polariton branches in
planar semiconductor microcavities has a pronounced effect on vortices in
polariton condensates. We show that the TE-TM splitting leads to the coupling
between the left and right half-vortices (vortices in the right and left
circular components of the condensate), that otherwise do not interact. We
analyze also the effect of linear polarization pinning resulted from a fixed
splitting between two perpendicular linear polarizations. In this case,
half-vortices acquire strings (solitons) attached to them. The half-vortices
with strings can be detected by observing the interference fringes of light
emitted from the cavity in two circular polarizations. The string affects the
fringes in both polarizations. Namely, the half-vortex is characterized by an
asymmetric fork-like dislocation in one circular polarization; the fringes in
the other circular polarization are continuous, but they are shifted by
crossing the string.Comment: 4 pages, 2 figs, Optics of Excitons in Confined Systems 11 (Madrid,
7-11 september 2009
Dynamical Casimir effect entangles artificial atoms
We show that the physics underlying the dynamical Casimir effect may generate
multipartite quantum correlations. To achieve it, we propose a circuit quantum
electrodynamics (cQED) scenario involving superconducting quantum interference
devices (SQUIDs), cavities, and superconducting qubits, also called artificial
atoms. Our results predict the generation of highly entangled states for two
and three superconducting qubits in different geometric configurations with
realistic parameters. This proposal paves the way for a scalable method of
multipartite entanglement generation in cavity networks through dynamical
Casimir physics.Comment: Improved version and references added. Accepted for publication in
Physical Review Letter
IGR J19294+1816: a new Be-X ray binary revealed through infrared spectroscopy
The aim of this work is to characterize the counterpart to the INTEGRAL High
Mass X-ray Binary candidate IGR J19294+1816 so as to establish its true nature.
We obtained H band spectra of the selected counterpart acquired with the NICS
instrument mounted on the Telescopio Nazionale Galileo (TNG) 3.5-m telescope
which represents the first infrared spectrum ever taken of this source. We
complement the spectral analysis with infrared photometry from UKIDSS, 2MASS,
WISE and NEOWISE databases. We classify the mass donor as a Be star.
Subsequently, we compute its distance by properly taking into account the
contamination produced by the circumstellar envelope. The findings indicate
that IGR J19294+1816 is a transient source with a B1Ve donor at a distance of
kpc, and luminosities of the order of erg s,
displaying the typical behaviour of a Be X-ray binary.Comment: 8 pages, 6 figures, accepted to be published in MNRA
The quantum Rabi model in a superfluid Bose-Einstein condensate
We propose a quantum simulation of the quantum Rabi model in an atomic
quantum dot, which is a single atom in a tight optical trap coupled to the
quasiparticle modes of a superfluid Bose-Einstein condensate. This widely
tunable setup allows to simulate the ultrastrong coupling regime of
light-matter interaction in a system which enjoys an amenable characteristic
timescale, paving the way for an experimental analysis of the transition
between the Jaynes-Cummings and the quantum Rabi dynamics using cold-atom
systems. Our scheme can be naturally extended to simulate multi-qubit quantum
Rabi models. In particular, we discuss the appearance of effective two-qubit
interactions due to phononic exchange, among other features.Comment: Improved version and references adde
Ensemble Quantum Computation with atoms in periodic potentials
We show how to perform universal quantum computation with atoms confined in
optical lattices which works both in the presence of defects and without
individual addressing. The method is based on using the defects in the lattice,
wherever they are, both to ``mark'' different copies on which ensemble quantum
computation is carried out and to define pointer atoms which perform the
quantum gates. We also show how to overcome the problem of scalability on this
system
Quantum computation with trapped ions in an optical cavity
Two-qubit logical gates are proposed on the basis of two atoms trapped in a
cavity setup. Losses in the interaction by spontaneous transitions are
efficiently suppressed by employing adiabatic transitions and the Zeno effect.
Dynamical and geometrical conditional phase gates are suggested. This method
provides fidelity and a success rate of its gates very close to unity. Hence,
it is suitable for performing quantum computation.Comment: 4 pages, 5 figures, REVTEX, second part modified, typos correcte
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