Multiple symbol differential detection

A differential detection technique for multiple phase shift keying (MPSK) signals is provided which uses a multiple symbol observation interval on the basis of which a joint decision is made regarding the phase of the received symbols. In accordance with the invention, a first difference phase is created between first and second received symbols. Next, the first difference phase is correlated with the possible values thereof to provide a first plurality of intermediate output signals. A second difference phase is next created between second and third received symbols. The second difference phase is correlated with plural possible values thereof to provide a second plurality of intermediate output signals. Next, a third difference phase is created between the first and third symbols. The third difference phase is correlated with plural possible values thereof to provide a third plurality of intermediate output signals. Each of the first plurality of intermediate outputs are combined with each of the second plurality of intermediate outputs and each of the third plurality of intermediate outputs to provide a plurality of possible output values. Finally, a joint decision is made by choosing from the plurality of possible output values the value which represents the best combined correlation of the first, second and third difference values with the possible values thereof

Role of the relative phase in the merging of two independent Bose-Einstein condensates

We study the merging of two independent Bose-Einstein condensates with arbitrary initial phase difference, in the framework of a one-dimensional time-dependent Gross-Pitaevskii model. The role of the initial phase difference in the process is discussed, and various types of phase-sensitive excitations are identified.Comment: 19 Pages, 7 figure

Analytical investigation for multiplicity difference correlators under QGP phase transition

It is suggested that the study of multiplicity difference correlators between two well-separated bins in high-energy heavy-ion collisions can be used as a means to detect evidence of a quark-hadron phase transition. Analytical expressions for the scaled factorial moments of multiplicity difference distribution are obtained in a kinetical region ${\bar s}\le 0.3$ within Ginzburg-Landau description. It is shown that the scaling behaviors between the moments are still valid, though the behaviors of the moments with respect to the bin size are completely different from the so-called intermittency patterns. A universal exponent $\gamma$ is given to describe the dynamical fluctuations in the phase transition.Comment: 5 pages, RevTeX, three figures in EPS forma

Spontaneous photon emission stimulated by two Bose condensates

We show that the phase difference of two overlapping ground state Bose-Einstein condensates can effect the optical spontaneous emission rate of excited atoms. Depending on the phase difference the atom stimulated spontaneous emission rate can vary between zero and the rate corresponding to all the ground state atoms in a single condensate. Besides giving control over spontaneous emission this provides an optical method for detecting the condensate phase difference. It differs from previous methods in that no light fields are applied. Instead the light is spontaneously emitted when excited atoms make a transition into either condensate.Comment: 14 pages, 2 postscript figures, Revtex. Corrections and significant additions in revisio

Pulsed phase locked loop strain monitor

The RF output of a voltage controlled oscillator (VCO) is periodically gated to a transducer which produces acoustic waves in a bolt. The reflected acoustic waves are converted to electrical signals by the transducer and gated to a mixer which also receives the output from the VCO and produces an output which is filtered by a low pass filter. The output of filter is a dc signal proportional to the phase difference change from a fixed phase difference between the two input signals to the mixer. This dc signal is sampled at an instant and held by circuit in response to the "P" signal. The output of the circuit is integrated and then applied to the VCO to change the frequency of the VCO such that the phase difference between the two inputs to the mixer remains at the fixed phase difference. The frequency of the VCO is a measure of the change in strain of the bolt

Optical stabilization of voltage fluctuations in half-Josephson lasers

A recently proposed device, dubbed half-Josephson laser, provides a phase-lock between the optical phase and the superconducting phase difference between the leads of the device. In this paper we propose to utilize this phase-lock for stabilization of voltage fluctuations, by two optical feedback schemes. The first scheme involves a single half-Josephson laser and allows to significantly decrease the diffusion coefficient of the superconducting phase difference. The second scheme involves a stable optical source and a fluctuating half-Josephson laser and permits quenching of the diffusion of the relative phase of the lasers. This opens up perspectives of the optical control of the superconducting phase and voltage fluctuations.Comment: 6 pages, 3 figure

Nonlocal mixing of supercurrents in Josephson ballistic point contact

We study coherent current states in the mesoscopic superconducting weak link simultaneously subjected to the order parameter phase difference on the contact and to the tangential to the junction interface superfluid velocity in the banks. The Josephson current-phase relation controlled by the external transport current is obtained. At phase difference close to pi the nonlocal nature of the Josephson phase-dependent current results in the appearance of two vortexlike states in the vicinity of the contact.Comment: 4 pages, 6 figures; to be published in Phys. Rev. B; e-mail: [email protected]