We investigate time-modulated EPR entangled states and intensity quantum correlation of twin light beams in application to time-resolved quantum communication. As a proper device generating such states, the nondegenerate optical parametric oscillator driven by the time-modulated pump field is considered.
We investigate time-modulation of continuous variable (CV) quantum states of light fields in application to time-resolved quantum communications. As realizations, we consider EPR entangled states of light as well as correlated twin beams generated in nondegenerate optical parametric oscillator (NOPO) subjected by a sequence of laser pulses. We demonstrate that time-modulation of a pump field essentially improves the degrees of both cv entanglement and intensity quantum correlation in NOPO doing them beyond the standard limits.
We investigate semiclassical dynamics and quantum properties of light beams generated in time-modulated nondegenerate optical parametric oscillator (NOPO). Having in view production of continuous-variable (CV) entangled states of light beams we propose two experimentally feasible schemes of NOPO: (i) driven by continuously modulated pump field; (ii) under action of a periodic sequence of identical laser pulses. It is shown that the time modulation of pump field amplitude essentially improves the degree of CV entanglement in NOPO. On the whole the level of integral two-mode squeezing, which characterizes the degree of CV entanglement, goes below the standard limit established in an ordinary NOPO with monochromatic pumping. We develop semiclassical and quantum theories of these devices for both below- and above-threshold regimes of generation. Properties of CV entanglement for various operational regimes of the devices are discussed in the time domain in application to time-resolved quantum information technologies. Our analytical results are in well agreement with the results of numerical simulation and support a concept of CV entangled states of time-modulated light beams.
We propose periodically-modulated entangled states of light and show that they can be generated in two experimentally feasible schemes of nondegenerate optical parametric oscillator (NOPO): (i) driven by continuously modulated pump field; (ii) under action of a periodic sequence of identical laser pulses. We show that the time-modulation of the pump field amplitude essentially improves the degree of continuous-variable entanglement in NOPO. We develop semiclassical and quantum theories of these devices for both below- and above-threshold regimes. Our analytical results are in well agrement with numerical simulation and support a concept of time-modulated entangled states.
Quantum entanglement and intensity correlations in continuous variable (CV) regimes have investigated in the time domain in addition to many analogous investigations performed in the frequency domain. The specific signatures of time-resolved CV quadrature entanglement and intensity difference squeezing have been analyzed for periodically-pulsed optical parametric oscillator (OPO). An application to quantum key distribution scheme based on intensity correlation of twin beams has also been considered.
It has been recently shown theoretically1 and experimentally2 that nondegenerate optical parametric oscillators generate above threshold intense and highly correlated twin beams. More precisely, the noise on the difference between the intensities of the two beams is well below the shot noise for noise frequencies inside the cavity bandwidth. An application of this quantum correlation is to measure the intensity of one beam and use this information to correct the fluctuations of the other beam by optoelectronic means (photodiode, amplifier, and electrooptic modulator). The correction may be applied either on the pumping beam (feedback correction) or directly on the twin beam itself (feed-forward correction).