Yu. M. Golubev

Quantum interference in atomic vapor controlled by a magnetic field

We have shown that quantum interference in a driven quasi-degenerate two-level atomic system can be controlled by an externally applied magnetic field. We demonstrate that the mechanism of optical control is based on quantum interference, which allows one to implement both electromagnetically induced transparency and electromagnetically induced absorption (EIA) in one atomic system. The experimental realization is suggested.

Quantum correlations and fluctuations in the pulsed light produced by a synchronously pumped optical parametric oscillator below its oscillation threshold

Abstract. We present a simple quantum theory for the pulsed light generated by a synchronously pumped optical parametric oscillator (SPOPO) in the degenerate case where the signal and idler trains of pulses coincide, below threshold and neglecting all dispersion effects. Our main goal is to precise in the obtained quantum effects, which ones are identical to the c.w. case and which ones are specific to the SPOPO. We demonstrate in particular that the temporal correlations have interesting peculiarities: the quantum fluctuations at different times within the same pulse turn out to be totally not correlated, whereas they are correlated between nearby pulses at times that are placed in the same position relative to the center of the pulses. The number of significantly correlated pulses is of the order of cavity finesse. We show also that there is perfect squeezing at noise frequencies

Pure and mixed states in degenerate parametric oscillation

\Omega_m

Broadband squeezed light from phase-locked single-mode sub-Poissonian lasers

= 2πm/TR (m = 0, 1, 2,

Storage and retrieval of squeezing in multimode resonant quantum memories

\ldots

Quadrature squeezing in an isolated pulse of light

where TR is the pulse train period) when one approaches the threshold from below on the signal field quadrature measured by a balanced homodyne detection with a local oscillator of very short duration compared to the SPOPO pulse length.

Quantum parallel dense coding of optical images

The degree of purity of the quantum state of electromagnetic field at the output of a degenerate optical parametric oscillator is theoretically analyzed. It is shown that, in the subthreshold and significantly suprathreshold modes, the degree of purity of the state of pairs of waves with frequencies ωs ± Ω (ωs is the signal mode frequency) is unity. Based on this fact, it is concluded that these pairs of waves parametrically develop independent of any other such pairs. At the same time, in the suprathreshold mode near the oscillation threshold, the degree of purity of wave pairs can be much smaller than unity. However, consideration of a tetrad of waves with frequencies ωs ± Ω and ωp ± Ω shows that this system is in a pure state, which indicates its independent development.

Kinetic theory of a super-radiating laser

We consider sub-Poissonian single-mode laser with external synchronization and analyze its applicability to the problems of quantum information. Using Heisenberg-Langevin theory we calculate the quadrature variances of the field emitted by this laser. It is shown that such systems can demonstrate strong quadrature squeezing. Taking into account that the emitted field is temporally multi-mode the application of such sources to multichannel quantum teleportation and dense coding protocols is discussed.

Entangled states of signal pulses in multimode quantum memory

In this article the ability to record, store, and read out the quantum properties of light is studied. The discussion is based on high-speed and adiabatic models of quantum memory in lambdaconfiguration and in the limit of strong resonance. We show that in this case the equality between efficiency and squeezing ratio, predicted by the simple beamsplitter model, is broken. The requirement of the maximum squeezing in the output pulse should not be accompanied by the requirement of maximum efficiency of memory, as in the beamsplitter model. We have demonstrated a high output pulse squeezing, when the efficiency reached only about 50%. Comprehension of this ”paradox” is achieved on the basis of mode analysis. The memories eigenmodes, which have an impact on the memory process, are found numerically. Also, the spectral analysis of modes was performed to match the spectral width of the input signal to the capacities of the memories.

Quantum correlations of pulses of optical parametric oscillator synchronously pumped above threshold

Quantum properties of pulsed radiation obtained by cutting out a part of the signal from steady-state squeezed-light sources are investigated. The considered sources include a degenerate optical parametric oscillator, a sub-Poissonian injection-locked laser, and a synchronously pumped femtosecond optical parametric oscillator. Based on the statistical properties of steady-state radiation from these sources, we analyzed to what extent preservation of these properties is sensitive to the observation time.