Entangled light in transition through the generation threshold

Abstract

We investigate continuous variable entangling resources on the base of two-mode squeezing for all operational regimes of a nondegenerate optical parametric oscillator with allowance for quantum noise of arbitrary level. The results for the quadrature variances of a pair of generated modes are obtained by using the exact steady-state solution of Fokker-Planck equation for the complex Pquasiprobability distribution function. We find a simple expression for the squeezed variances in the near-threshold range and conclude that the maximal two-mode squeezing reaches 50% relative to the level of vacuum fluctuations and is achieved at the pump field intensity close to the generation threshold. The distinction between the degree of two-mode squeezing for monostable and bistable operational regimes is cleared up. [2,3]). An important example provides entangled Einstein-Podolski-Rosen (EPR) state of orthogonally polarized but frequency degenerate beams, efficiently generated via nonlinear optical process of parametric down-conversion. It has been pointed out in [4] and has been demonstrated experimentally in [5] for CV, employing sub-threshold nondegenarate optical parametric oscillator (NOPO). Then a CV entanglement source was built from two independent quadrature squeezed beams combined on a beam-splitter [2]. The generation of CV EPR entanglement using an optical fibre interferometer is also demonstrated [6]. It should be noted that so far most experimental realizations of the CV entanglement on NOPO's have only been operated below threshold. A natural next step is the extension of these investigations to laser-like systems generating entangled bright-light states. Unfortunately, both theoretical and experimental studies of these problems are very complicated and only rare examples are known up to now. Many efforts have been devoted to the study of intensity correlated twin beams from NOPO above threshold [7]. The conditional generation of sub-Poissonian light from bright twin beams in the CV regime is experimentally demonstrated in [8]. Further experimental studies of bright two-mode entangled state from cw nondegenerate optical parametric amplifier have been made in Refs.[9]. The generation of CV polarization entanglement by mixing a pair of polarization squeezed beams is realized * gkryuchk@server.physdep.r.am † leman@ipr.sci.amThe purpose of this paper is to investigate physical properties and the presence of CV entanglement for NOPO in its transition through the generation threshold as well as in the regime of lasing. One of the principal problems in this study is the description of quantum fluctuations. In most theoretical works nonclassical effects and entanglement resources of nonlinear quantum systems are usually described within linear treatment of quantum noise. It is obvious that such approach does not describe the critical ranges (threshold, point of multistability, etc) where the level of quantum noise increases substantially. We use a more adequate approach within the framework of exact nonlinear treatme...

Three-photon states in phase space

“…Application of this method for the numerical study of open quantum-optical systems are shown, in particular, in the works [25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Detailed analysis of this three-photon radiation process in case of monochromatic pump field ( ) 1 f t = is presented in the work [16].…”

Preparation of Distant Quantum Entanglement and One‐way Quantum Steering in Hybrid Cavity‐Magnonics‐and‐Cavity‐Optomechanical Systems

“…[46] Therefore, the operator can be approximated near the steady-state value as: O = O s + 𝛿O, where O = a i , m, b, with O s representing the mean value of O and 𝛿O denoting the fluctuation of O. After we substitute the approximate operator to QLE, we can easily obtain steady-state solution considered in the monostable region [47] a 1s = −𝜀 1…”

“…[ 46 ] Therefore, the operator can be approximated near the steady‐state value as: $$O=O_s+\delta O$$, where $$O=a_{i}, m, b$$, with $$O_s$$ representing the mean value of $$O$$ and $$\delta O$$ denoting the fluctuation of $$O$$. After we substitute the approximate operator to QLE, we can easily obtain steady‐state solution considered in the monostable region [ 47 ] …”

Web Portal for Photonic Technologies Using Grid Infrastructures

“…The application has been constructed on the base of the numerical simulation method of quantum trajectories or Quantum State Diffusion (QSD) method [3]. The corresponding library includes investigation of quantum dissipative chaos, bistability and bifurcations [4][5][6][7][8], quantum stochastic resonance [9], long-lived quantum interference in periodically modulated oscillatory systems [10], engineering of Fock states and qubits in nonlinear oscillators [11] elaboration of devices generating intensive entangled light beams for quantum communications [12][13][14][15] as well as production of threephoton entangled states in parametric devices [16][17][18] and numerical simulation of complex quantum optical systems (see, particularly, interaction of an atom with bichromatic laser field [19][20][21], cascaded processes [22] and photonics in ion-trap systems [23]).…”

“…The density operator using an expansion of the state vector  in a truncated basis of Fock's number states of a harmonic oscillator (photonic states) is calculated. In this way, the ECAQT library corresponding to QSD method has been applied for various physical problems [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18].…”