Proposal for entangling remote micromechanical oscillators via optical measurements

We propose an experiment to create and verify entanglement between remote mechanical objects by use of an optomechanical interferometer. Two optical cavities, each coupled to a separate mechanical oscillator, are coherently driven such that the oscillators are laser cooled to the quantum regime. The entanglement is induced by optical measurement and comes about by combining the output from the two cavities to erase which-path information. It can be verified through measurements of degrees of second-order coherence of the optical output field. The experiment is feasible in the regime of weak optomechanical coupling. Realistic parameters for the membrane-in-the-middle geometry suggest entangled state lifetimes on the order of milliseconds.Comment: 4 pages, 2 figures + supplementary material (7 pages, 2 figs). Updates in v2: New Eq. (7) and Fig. 1 - results unchanged. Added supplementary material with various details. Updates in v3: Minor changes, journal ref. adde

Modulational instability of partially coherent signals in electrical transmission lines

We present an investigation of the modulational instability of partially coherent signals in electrical transmission lines. Starting from the modified Ginzburg-Landau equations and the Wigner-Moyal representation, we derive a nonlinear dispersion relation for the modulational instability. It is found that the effect of signal broadbandness reduces the growth rate of the modulational instability.Comment: 5 pages, 1 figure, to appear in Physical Review

Effects of frequency correlation in linear optical entangling gate operated with independent photons

Bose-Einstein coalescence of independent photons at the surface of a beam splitter is the physical process that allows linear optical quantum gates to be built. When distinct parametric down-conversion events are used as an independent photon source, distinguishability arises form the energy correlation of each photon with its twin. We find that increasing the pump bandwidth may help in improving the visibility of non-classical interference and reaching a level of near perfect indistinguishability. PACS: 03.67.Mn, 42.65.Lm, 42.50.St.Comment: Replaced with published versio

Propagation of nonclassical light through an absorbing and dispersive slab

We calculate the effects of perpendicular propagation through a dispersive and absorbing dielectric slab at arbitrary temperatures on specific nonclassical properties of an incident light field. The transmitted signal is assumed to be measured by a detector that receives radiation only from the direction normal to thr slab surfaces. Squeezing and nonclassical counting statistics of the transmitted light are evaluated for continuous-wave squeezed states incident on both sides of the slab. The degree of second-order coherence is instead evaluated for an N-photon incident pulse, and the effects of transmission through the slab on its antibunching are calculated. [S1050-2947(99)06701-3]

Coherent flash of light emitted by a cold atomic cloud

When a resonant laser sent on an optically thick cold atomic cloud is abruptly switched off, a coherent flash of light is emitted in the forward direction. This transient phenomenon is observed due to the highly resonant character of the atomic scatterers. We analyze quantitatively its spatio-temporal properties and show very good agreement with theoretical predictions. Based on complementary experiments, the phase of the coherent field is reconstructed without interferometric tools.Comment: Submitted to Phys. Rev. Let

Broadening the bandwidth of entangled photons: a step towards the generation of extremely short biphotons

We demonstrate a technique that allows to fully control the bandwidth of entangled photons independently of the frequency band of interest and of the nonlinear crystal. We show that this technique allows to generate nearly transform-limited biphotons with almost one octave of bandwidth (hundreds of THz) which corresponds to correlation times of just a few femtoseconds. The presented method becomes an enabling tool for attosecond entangled-photons quantum optics. The technique can also be used to generate paired photons with a very high degree of entanglement.Comment: 4 page

Backgrounds of squeezed relic photons and their spatial correlations

We discuss the production of multi-photons squeezed states induced by the time variation of the (Abelian) gauge coupling constant in a string cosmological context. Within a fully quantum mechanical approach we solve the time evolution of the mean number of produced photons in terms of the squeezing parameters and in terms of the gauge coupling. We compute the first (amplitude interference) and second order (intensity interference) correlation functions of the magnetic part of the photon background. The photons produced thanks to the variation of the dilaton coupling are strongly bunched for the realistic case where the growth of the dilaton coupling is required to explain the presence of large scale magnetic fields and, possibly of a Faraday rotation of the Cosmic Microwave Background.Comment: 9 pages in LaTex styl

On Wheeler's delayed-choice Gedankenexperiment and its laboratory realization

Here, we present an analysis and interpretation of the experiment performed by Jacques et al. (2007 Science 315, 966), which represents a realization of Wheeler's delayed-choice Gedankenexperiment. Our analysis is based on the evolution of the photon state, since the photon enters into the Mach-Zehnder interferometer with a removable beam-splitter until it exits. Given the same incident photon state onto the output beam-splitter, BS_output, the photon's state at the exit will be very different depending on whether BS_output is on or off. Hence, the statistics of photon counts collected by the two detectors, positioned along orthogonal directions at the exit of the interferometer, is also going to be very different in either case. Therefore, it is not that the choice of inserting (on) or removing (off) a beam-splitter leads to a delayed influence on the photon behavior before arriving at the beam-splitter, but that such a choice influences the photon state at and after BS_output, i.e., after it has exited from the Mach-Zehnder interferometer. The random on/off choice at BS_output has no delayed effect on the photon to behave as a wave or a corpuscle at the entrance and inside the interferometer, but influences the subsequent evolution of the photon state incident onto BS_output.Comment: 7 pages, 4 figure

Economic evaluation of the treatment of grade II haemorrhoids : a comparison of stapled haemorrhoidopexy and rubber band ligation.

The definitive version is available at www3.interscience.wiley.comPeer reviewedPostprin

Damped Population Oscillation in a Spontaneously Decaying Two-Level Atom Coupled to a Monochromatic Field

We investigate the time evolution of atomic population in a two-level atom driven by a monochromatic radiation field, taking spontaneous emission into account. The Rabi oscillation exhibits amplitude damping in time caused by spontaneous emission. We show that the semiclassical master equation leads in general to an overestimation of the damping rate and that a correct quantitative description of the damped Rabi oscillation can thus be obtained only with a full quantum mechanical theory.Comment: 5 pages, 5 figure