135,710 research outputs found
Continuous variable entanglement of phase locked light beams
We explore in detail the possibility of intracavity generation of
continuous-variable (CV) entangled states of light beams under mode
phase-locked conditions. We show that such quantum states can be generated in
self-phase locked nondegenerate optical parametric oscillator (NOPO) based on a
type-II phase-matched down-conversion combined with linear mixer of two
orthogonally polarized modes of the subharmonics in a cavity. A quantum theory
of this device, recently realized in the experiment, is developed for both
sub-threshold and above-threshold operational regimes. We show that the system
providing high level phase coherence between two generated modes, unlike to the
ordinary NOPO, also exhibits different types of quantum correlations between
photon numbers and phases of these modes. We quantify the CV entanglement as
two-mode squeezing and show that the maximal degree of the integral two-mode
squeezing(that is 50% relative to the level of vacuum fluctuations) is achieved
at the pump field intensity close to the generation threshold of self-phase
locked NOPO, provided that the constant of linear coupling between the two
polarizations is much less than the mode detunings. The peculiarities of CV
entanglement for the case of unitary, non-dissipative dynamics of the system
under consideration is also cleared up
Quadrature entanglement and photon-number correlations accompanied by phase-locking
We investigate quantum properties of phase-locked light beams generated in a
nondegenerate optical parametric oscillator (NOPO) with an intracavity
waveplate. This investigation continuous our previous analysis presented in
Phys.Rev.A 69, 05814 (2004), and involves problems of continuous-variable
quadrature entanglement in the spectral domain, photon-number correlations as
well as the signatures of phase-locking in the Wigner function. We study the
role of phase-localizing processes on the quantum correlation effects. The
peculiarities of phase-locked NOPO in the self-pulsing instability operational
regime are also cleared up. The results are obtained in both the
P-representation as a quantum-mechanical calculation in the framework of
stochastic equations of motion, and also by using numerical simulation based on
the method of quantum state diffusion.Comment: Subm. to PR
Absolute and differential measurement of water vapor supersaturation using a commercial thin-film sensor
We describe a technique for measuring the water vapor supersaturation of normal air over a temperature range of –40<~T<~0 °C. The measurements use an inexpensive commercial hygrometer which is based on a thin-film capacitive sensor. The time required for the sensor to reach equilibrium was found to increase exponentially with decreasing sensor temperature, exceeding 2 min for T = –30 °C; however, the water vapor sensitivity of the device remained high down to this temperature. After calibrating our measurement procedure, we found residual scatter in the data corresponding to an uncertainty in the absolute water vapor pressure of about ±15%. This scatter was due mainly to long-term drift, which appeared to be intrinsic to the capacitive thin-film sensor. The origin of this drift is not clear, but it effectively limits the applicability of this instrument for absolute measurements. We also found, however, that the high sensitivity of the thin-film sensor makes it rather well suited for differential measurements. By comparing supersaturated and saturated air at the same temperature we obtained a relative measurement uncertainty of about ±1.5%, an order of magnitude better than the absolute measurements
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