3,184 research outputs found
Dynamical Casimir Effect in two-atom cavity QED
We study analytically and numerically the dynamical Casimir effect in a
cavity containing two stationary 2-level atoms that interact with the resonance
field mode via the Tavis-Cummings Hamiltonian. We determine the modulation
frequencies for which the field and atomic excitations are generated and study
the corresponding dynamical behaviors in the absence of damping. It is shown
that the two-atom setup allows for monitoring of photon generation without
interrupting the growth, and different entangled states can be generated during
the process.Comment: 4+ pages, 2 figure
Approximate analytical results on the cavity dynamical Casimir effect in the presence of a two-level atom
We study analytically the photon generation from vacuum due to the Dynamical
Casimir effect in a cavity with a two-level atom, prepared initially in an
arbitrary pure state. Performing small unitary transformations we obtain closed
analytical expressions for the probability amplitudes and other important
quantities in the resonant/dispersive regimes.Comment: 5 pages, 2 figure
Smooth quantum-classical transition in photon subtraction and addition processes
Recently Parigi et al. [Science 317, 1890 (2007)] implemented experimentally
the photon subtraction and addition processes from/to a light field in a
conditional way, when the required operations were produced successfully only
upon the positive outcome of a separate measurement. It was verified that for a
low intensity beam (quantum regime) the bosonic annihilation operator does
indeed describe a single photon subtraction, while the creation operator
describes a photon addition. Nonetheless, the exact formal expressions for
these operations do not always reduce to these simple identifications, and in
this connection here we deduce the general superoperators for multiple photons
subtraction and addition processes and analyze the statistics of the resulting
states for classical field states having an arbitrary intensity. We obtain
closed analytical expressions and verify that for classical fields with high
intensity (classical regime) the operators that describe photon subtraction and
addition processes deviate significantly from simply annihilation and creation
operators. Complementarily, we analyze in details such a smooth
quantum-classical transition as function of beam intensity for both processes.Comment: 7 pages, 5 figures. To appear in Phys. Rev.
Amplification of Fluctuations in Unstable Systems with Disorder
We study the early-stage kinetics of thermodynamically unstable systems with
quenched disorder. We show analytically that the growth of initial fluctuations
is amplified by the presence of disorder. This is confirmed by numerical
simulations of morphological phase separation (MPS) in thin liquid films and
spinodal decomposition (SD) in binary mixtures. We also discuss the
experimental implications of our results.Comment: 15 pages, 4 figure
Controlling entanglement by direct quantum feedback
We discuss the generation of entanglement between electronic states of two
atoms in a cavity using direct quantum feedback schemes. We compare the effects
of different control Hamiltonians and detection processes in the performance of
entanglement production and show that the quantum-jump-based feedback proposed
by us in Phys. Rev. A {\bf 76} 010301(R) (2007) can protect highly entangled
states against decoherence. We provide analytical results that explain the
robustness of jump feedback, and also analyse the perspectives of experimental
implementation by scrutinising the effects of imperfections and approximations
in our model.Comment: 10 pages, 8 figures. To appear in PR
Microscopic models of quantum jump super-operators
We discuss the quantum jump operation in an open system, and show that jump
super-operators related to a system under measurement can be derived from the
interaction of that system with a quantum measurement apparatus. We give two
examples for the interaction of a monochromatic electromagnetic field in a
cavity (the system) with 2-level atoms and with a harmonic oscillator
(representing two different kinds of detectors). We show that derived quantum
jump super-operators have `nonlinear' form which depends on assumptions made
about the interaction between the system and the detector. A continuous
transition to the standard Srinivas--Davies form of the quantum jump
super-operatoris shown
Resonance fluorescence from an artificial atom in squeezed vacuum
We present an experimental realization of resonance fluorescence in squeezed
vacuum. We strongly couple microwave-frequency squeezed light to a
superconducting artificial atom and detect the resulting fluorescence with high
resolution enabled by a broadband traveling-wave parametric amplifier. We
investigate the fluorescence spectra in the weak and strong driving regimes,
observing up to 3.1 dB of reduction of the fluorescence linewidth below the
ordinary vacuum level and a dramatic dependence of the Mollow triplet spectrum
on the relative phase of the driving and squeezed vacuum fields. Our results
are in excellent agreement with predictions for spectra produced by a two-level
atom in squeezed vacuum [Phys. Rev. Lett. \textbf{58}, 2539-2542 (1987)],
demonstrating that resonance fluorescence offers a resource-efficient means to
characterize squeezing in cryogenic environments
Reproductive endocrine effects of intranasal administration of norethisterone to adult female rhesus monkeys (Macaca mulatta)
Intranasal administration of norethisterone at a daily dose of 9 ÎĽg between Days 5 and 14 of the menstrual cycles blocked ovulation in 10 out of 17 adult female monkeys. Serum concentrations of hormones indicated that ovulation was blocked due to a suppression of the mid-cycle, oestradiol-induced LH surge. Ovarian follicular activity in the treated menstrual cycles was not affected by norethisterone but there was a marked delay in the onset of the mid-cycle oestradiol surge in most of the treated animals. The duration of the menstrual cycle length after the oestradiol peak was significantly reduced in all the treated monkeys, indicative of a shortened luteal phase
Cavity Dynamical Casimir Effect in the presence of a three-level atom
We consider the scenario in which a damped three-level atom in the ladder or
V configurations is coupled to a single cavity mode whose vacuum state is
amplified by dint of the dynamical Casimir effect. We obtain approximate
analytical expressions and exact numerical results for the time-dependent
probabilities, demonstrating that the presence of the third level modifies the
photon statistics and its population can serve as a witness of photon
generation from vacuum.Comment: 7 pages, 4 figure
Coherent control of collective spontaneous emission in an extended atomic ensemble and quantum storage
Coherent control of collective spontaneous emission in an extended atomic
ensemble resonantly interacting with single-photon wave packets is analyzed. A
scheme for coherent manipulation of collective atomic states is developed such
that superradiant states of the atomic system can be converted into subradiant
ones and vice versa. Possible applications of such a scheme for optical quantum
state storage and single-photon wave packet shaping are discussed. It is shown
that also in the absence of inhomogeneous broadening of the resonant line,
single-photon wave packets with arbitrary pulse shape may be recorded as a
subradiant state and reconstructed even although the duration of the wave
packets is larger than the superradiant life-time. Specifically the
applicability for storing time-bin qubits, which are used in quantum
cryptography is analyzed.Comment: 11 pages, 4 figures, submitted to PR
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