4,337 research outputs found
Preventing Multipartite Disentanglement by Local Modulations
An entangled multipartite system coupled to a zero-temperature bath undergoes
rapid disentanglement in many realistic scenarios, due to local,
symmetry-breaking, differences in the particle-bath couplings. We show that
locally controlled perturbations, addressing each particle individually, can
impose a symmetry, and thus allow the existence of decoherence-free
multipartite entangled systems in zero-temperature environments.Comment: 5 pages, 2 figure
Fluorescence interferometry
We describe an interferometer based on fluorescent emission of radiation of
two qubits in quasi-one-dimensional modes. Such a system can be readily
realized with dipole emitters near conducting surface-plasmonic nanowires or
with superconducting qubits coupled to coplanar waveguide transmission lines.Comment: 7 pages, 2 figure
Quantum noise in optical interferometers
We study the photon counting noise in optical interferometers used for
gravitational wave detection. In order to reduce quantum noise a squeezed
vacuum is injected into the usually unused input port. It is investigated under
which conditions the gravitational wave signal may be amplified without
increasing counting noise concurrently. Such a possibility was suggested as a
consequence of the entanglement of the two output ports of a beam splitter. We
find that amplification without concurrent increase of noise is not possible
for reasonable squeezing parameters. Photon distributions for various beam
splitter angles and squeezing parameters are calculated.Comment: 15 pages, 7 figure
Spontaneous Generation of Photons in Transmission of Quantum Fields in PT Symmetric Optical Systems
We develop a rigorous mathematically consistent description of PT symmetric
optical systems by using second quantization. We demonstrate the possibility of
significant spontaneous generation of photons in PT symmetric systems. Further
we show the emergence of Hanbury-Brown Twiss (HBT) correlations in spontaneous
generation. We show that the spontaneous generation determines decisively the
nonclassical nature of fields in PT symmetric systems. Our work can be applied
to other systems like plasmonic structure where losses are compensated by gain
mechanisms.Comment: 4 pages, 5 figure
Nanosecond Dynamics of Single-Molecule Fluorescence Resonance Energy Transfer
Motivated by recent experiments on photon statistics from individual dye
pairs planted on biomolecules and coupled by fluorescence resonance energy
transfer (FRET), we show here that the FRET dynamics can be modelled by
Gaussian random processes with colored noise. Using Monte-Carlo numerical
simulations, the photon intensity correlations from the FRET pairs are
calculated, and are turned out to be very close to those observed in
experiment. The proposed stochastic description of FRET is consistent with
existing theories for microscopic dynamics of the biomolecule that carries the
FRET coupled dye pairs.Comment: 8 pages, 1 figure. accepted to J.Phys.Chem.
Radiation trapping in coherent media
We show that the effective decay rate of Zeeman coherence, generated in a
Rb87 vapor by linearly polarized laser light, increases significantly with the
atomic density. We explain this phenomenon as the result of radiation trapping.
Our study shows that radiation trapping must be taken into account to fully
understand many electromagnetically induced transparency experiments with
optically thick media
Ultra-bright omni-directional collective emission of correlated photon pairs from atomic vapors
Spontaneous four-wave mixing can generate highly correlated photon pairs from
atomic vapors. We show that multi-photon pumping of dipole-forbidden
transitions in a recoil-free geometry can result in ultra-bright pair-emission
in the full 4\pi solid angle, while strongly suppresses background Rayleigh
scattering and associated atomic heating, Such a system can produce photon
pairs at rates of ~ 10 ^12 per second, given only moderate optical depths of 10
~ 100, or alternatively, the system can generate paired photons with
sub-natural bandwidths at lower production rates. We derive a rate-equation
based theory of the collective atomic population and coherence dynamics, and
present numerical simulations for a toy model, as well as realistic model
systems based on 133 Cs and 171 Yb level structures. Lastly, we demonstrate
that dark-state adiabatic following (EIT) and/or timescale hierarchy protects
the paired photons from reabsorption as they propagate through an optically
thick sample
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