Nonclassical Correlation of Polarization Entangled Photons in a Biexciton-Exciton Cascade

We develop a theoretical model to study the Intensity-Intensity correlation of polarization entangled photons emitted in a biexciton-exciton cascade. We calculate the degree of correlation and show how polarization correlation are affected by the presence of dephasing and energy level splitting of the excitonic states. Our theoretical calculations are in agreement with the recent observation of polarization dependent Intensity-Intensity correlations from a single semiconductor quantum dot [R. M. Stevenson et. al., Nature 439, 179 (2006)] . Our model can be extended to study polarization entangled photon emission in coupled quantum dot systems

Quantum Entanglement Initiated Super Raman Scattering

It has now been possible to prepare chain of ions in an entangled state and thus question arises --- how the optical properties of a chain of entangled ions differ from say a chain of independent particles. We investigate nonlinear optical processes in such chains. We explicitly demonstrate the possibility of entanglement produced super Raman scattering. Our results in contrast to Dicke's work on superradiance are applicable to stimulated processes and are thus free from the standard complications of multimode quantum electrodynamics. Our results suggest the possibility of similar enhancement factors in other nonlinear processes like four wave mixing.Comment: 4 pages, 1 figur

Complementarity and Phase Distributions for Angular Momentum Systems

Interferences in the distributions of complementary variables for angular momentum - two level systems are discussed. A quantum phase distribution is introduced for angular momentum. Explicit results for the phase distributions and the number distributions for atomic coherent states, squeezed states and superpositions of coherent states are given. These results clearly demonstrate the issue of complementarity and provide us with results analogous to those for the radiation field.Comment: 9 pages, 3 figures available on request, replaced with minor typos corrected in abstract, to appear in Physics Letters

On wavenumber spectra for sound within subsonic jets

This paper clarifies the nature of sound spectra within subsonic jets. Three problems, of increasing complexity, are presented. Firstly, a point source is placed in a two-dimensional plug flow and the sound field is obtained analytically. Secondly, a point source is embedded in a diverging axisymmetric jet and the sound field is obtained by solving the linearised Euler equations. Finally, an analysis of the acoustic waves propagating through a turbulent jet obtained by direct numerical simulation is presented. In each problem, the pressure or density field are analysed in the frequency-wavenumber domain. It is found that acoustic waves can be classified into three main frequency-dependent groups. A physical justification is provided for this classification. The main conclusion is that, at low Strouhal numbers, acoustic waves satisfy the d'Alembertian dispersion relation.Comment: 20 pages, 9 figure

Quantum interference and non-locality of independent photons from disparate sources

We quantitatively investigate the non-classicality and non-locality of a whole new class of mixed disparate quantum and semiquantum photon sources at the quantum-classical boundary. The latter include photon added thermal and photon added coherent sources, experimentally investigated recently by Zavatta et al. [Phys. Rev. Lett. 103, 140406 (2009)]. The key quantity in our investigations is the visibility of the corresponding photon-photon correlation function. We present explicit results on the violations of the Cauchy-Schwarz inequality - which is a measure of nonclassicality - as well as of Bell-type inequalities.Comment: 9 pages, 3 figure

Stabilising entanglement by quantum jump-based feedback

We show that direct feedback based on quantum jump detection can be used to generate entangled steady states. We present a strategy that is insensitive to detection inefficiencies and robust against errors in the control Hamiltonian. This feedback procedure is also shown to overcome spontaneous emission effects by stabilising states with high degree of entanglement.Comment: 5 pages, 4 figure

Electromagnetically Induced Transparency with Quantized Fields in Optocavity Mechanics

We report electromagnetically induced transparency using quantized fields in optomechanical systems. The weak probe field is a narrow band squeezed field. We present a homodyne detection of EIT in the output quantum field. We find that the EIT dip exists even though the photon number in the squeezed vacuum is at the single photon level. The EIT with quantized fields can be seen even at temperatures of the order of 100 mK paving the way for using optomechanical systems as memory elements.Comment: 6 pages, 5 figure