Quantum Zeno effect in two coupled nonlinear optical processes

Consecutive nonlinear optical interactions consisting of two coupled parametric processes, namely, the nondegenerate spontaneous parametric down-conversion and up-conversion, are analyzed. The vacuum state of the input light is considered to be an unstable state decaying into a reservoir of down-converted modes, with one of the modes generated being continuously measured using the up-conversion process. Mean photon numbers at interacting frequencies are studied. Special attention is paid to the case where the nonlinear coupling coefficient for the up-conversion process is much larger than that for the nondegenerate spontaneous parametric down-conversion. It is shown that in this case the result of such consecutive interactions can be interpreted from the viewpoint of the quantum Zeno effect.     

Entanglement and Photon Anti-Bunching in Coupled Non-Degenerate Parametric Oscillators

We analytically and numerically show that the Hillery-Zubairy’s entanglement criterion is satisfied both below and above the threshold of coupled non-degenerate optical parametric oscillators (NOPOs) with strong nonlinear gain saturation and dissipative linear coupling. We investigated two cases: for large pump mode dissipation, below-threshold entanglement is possible only when the parametric interaction has an enough detuning among the signal, idler, and pump photon modes. On the other hand, for a large dissipative coupling, below-threshold entanglement is possible even when there is no detuning in the parametric interaction. In both cases, a non-Gaussian state entanglement criterion is satisfied even at the threshold. Recent progress in nano-photonic devices might make it possible to experimentally demonstrate this phase transition in a coherent XY machine with quantum correlations.     

Simultaneous parametric generation and up-conversion of entangled optical images

A quantum theory of parametric amplification and frequency conversion of an optical image in coupled nonlinear optical processes that include one parametric amplification process at high-frequency pumping and two up-conversion processes in the same pump field is developed. The field momentum operator that takes into account the diffraction and group velocities of the waves is used to derive the quantum equations related to the spatial dynamics of the images during the interaction. An optical scheme for the amplification and conversion of a close image is considered. The mean photon number density and signal-to-noise ratio are calculated in the fixed-pump-field approximation for images at various frequencies. It has been established that the signal-to-noise ratio decreases with increasing interaction length in the amplified image and increases in the images at the generated frequencies, tending to asymptotic values for all interacting waves. The variance of the difference of the numbers of photons is calculated for various pairs of frequencies. The quantum entanglement of the optical images formed in a high-frequency pump field is shown to be converted to higher frequencies during the generation of sum frequencies. Thus, two pairs of entangled optical images are produced in the process considered.     

Two mode photon bunching effect as witness of quantum criticality in circuit QED

We suggest a scheme to probe critical phenomena at a quantum phase transition (QPT) using the quantum correlation of two photonic modes simultaneously coupled to a critical system. As an experimentally accessible physical implementation, a circuit QED system is formed by a capacitively coupled Josephson junction qubit array interacting with one superconducting transmission line resonator (TLR). It realizes an Ising chain in the transverse field (ICTF) which interacts with the two magnetic modes propagating in the TLR. We demonstrate that in the vicinity of criticality the originally independent fields tend to display photon bunching effects due to their interaction with the ICTF. Thus, the occurrence of the QPT is reflected by the quantum characteristics of the photonic fields.     

Tomographic measurement of joint photon statistics of the twin-beam quantum state

We report the first measurement of the joint photon-number probability distribution for a two-mode quantum state created by a nondegenerate optical parametric amplifier. The measured distributions exhibit up to 1.9 dB of quantum correlation between the signal and idler photon numbers, whereas the marginal distributions are thermal as expected for parametric fluorescence.     

Perfect photon absorption based on the optical parametric process

The perfect photon absorption is studied in a cavity quantum electrodynamics(CQED) system, in which an optical parameter amplifier(OPA) is coupled to the cavity mode. This makes it possible to control the optical phase to realize the perfect photon absorption. It is found that in the presence of one and two injected fields, the perfect photon absorption is present in these two cases and can be controlled by adjusting the parametric phase. Moreover, different from the previous predictions of perfect photon absorption in atomic CQED systems, the perfect photon absorption can be changed significantly by the relative phase. Our work provides a new platform to use the parametric processes to make an available way to control the behaviors of photons and to take advantage of the optical phase to achieve the perfect photon absorption.     

Some properties and applications of biphoton states of three-mode light

Statistical properties, generation, and applications of three-mode biphoton fields with no more than one photon in each mode are discussed. Such field states have sub-Poissonian photon statistics and can be squeezed and entangled. The modes that simultaneously exhibit these properties in measurements are indicated. Two setups for generating such states via spontaneous parametric down-conversion are described. It is shown that the field states discussed in this study provide a quantum channel for teleportation, dense coding, and quantum key distribution.     

Contribution to the theory of parametric generation of cyclotron radiation

A linear theory of the cyclotron parametric instability in systems which are classical analogues of quantum lasers without inversion is developed. The cyclotron interaction of different types of modulated electron beams with a bichromatic field, produced by waves propagating at an angle with respect to a constant magnetic field, is investigated. It is shown that simultaneous amplification of two parametrically coupled modes with different frequencies and positive energy is possible in this system with modulation of the active and reactive components of the susceptibility of an electronic ensemble. The results obtained are important from the standpoint of the general theory of radiation processes in electron beams and plasma and for the advancement of microwave electronics.     

Quantum coherence and entangled states in intracavity third subharmonic generation process

The dynamics of correlation of photon number fluctuations of interacting modes for the process of intracavity third subharmonic generation is investigated. It is shown that the entangled field states by the variables of photon number can be obtained in this system. The quantum dynamics of the photons number, the quantum entropy and the Wigner function of the stationary states of the fundamental mode and the third subharmonic mode have also been studied. It is found that the dynamics of these quantities depends highly on the value of the coupling coefficient of the interacting modes. It is shown that at long interaction times and for the large values of the coupling coefficient of the modes, the mode of the third subharmonic is localized in the three-component state with the same probability of detection of the mode in each component of the state. The quantum entropy of the state is less than the maximal entropy of the three-component state ln3, which points out the presence of quantum mechanical interference between the components of the state of third subharmonic mode.     

Quantum state transfer between distant atoms via selectivity photon emission and absorption progresses

We proposed a simple scheme to deterministically generate three-dimensional (3D) quantum state transfer (QST) between two spatially atoms based on the selectivity photon emission and absorption progresses. In the present scheme, two M-type five-level atoms are trapped into two cavities connected by a fiber. By quantitatively discussing the evolution of system, we show that the effects of atom's spontaneous decay and photon leakage out of fiber can be suppressed in our scheme due to the presence of virtual excited processes in atom and fiber modes. Moreover, we also show that the present scheme can be extended to realize QST between distant nodes in a coupled array of optical cavity, which is very useful for the progress of the quantum information network.     

偶极子位置及偏振对激发光子晶体H1微腔的影响

光子晶体微腔和量子点的集成是实现量子信息处理非常具有潜力的平台之一,利用微腔和量子点的耦合可以制备纠缠光子对,实现对量子态的操控.因为光子晶体微腔具有品质因子高、模场体积小等优点,可以极大地增强光与物质之间的相互作用,从而易于实现量子态在不同物理体系之间的转换.通过单量子点和光子晶体H1微腔的耦合可以产生纠缠光子对,因为H1微腔具有简并的、模式偏振正交的基态模式.通常微腔模式的激发随着量子点在微腔中的位置变化而改变,本文用时域有限差分方法研究了偶极子光源的位置及偏振对激发光子晶体H1微腔模式的影响.结果表明:通过改变偶极子光源位置可以选择性地激发H1微腔简并模式中的一个;具有某一偏振的偶极子光源只能激发相应偏振的微腔模式;模式激发强度的大小也是由偶极子光源在微腔中的位置决定的.鉴于目前量子点在微腔中的位置尚不能精确控制,所以微腔模式受激发光源位置的影响的研究具有重要意义.     

非旋波近似中两能级原子与热库相互作用时原子的消相干特性

两能级原子与外部环境（热库）相互作用时,采用非旋波近似,研究原子与热辐射场单光子和双光子作用过程,利用小系统与库耦合行为的量子理论,计算原子约化密度矩阵非对角元,分析原子状态的消相干特性。     

Second order parametric processes in nonlinear silica microspheres

We analyze second order parametric processes in a silica microsphere coated with radially aligned nonlinear optical molecules. In a high-Q nonlinear microsphere, we discover that it is possible to achieve ultralow threshold parametric oscillation that obeys the rule of angular momentum conservation. Based on symmetry considerations, one can also implement parametric processes that naturally generate quantum entangled photon pairs. Practical issues regarding implementation of the nonlinear microsphere are also discussed.     

Spinning microresonator-induced chiral optical transmission

Chiral quantum optics is a new research area in light-matter interaction that depends on the direction of light propagation and offers a new path for the quantum regulation of light-matter interactions. In this paper, we study a spinning Kerr-type microresonator coupled with Λ-type atom ensembles, which are driven in opposite directions to generate asymmetric photon statistics. We find that a photon blockade can only be generated by driving the spinning resonator on right side without driving the spinning microresonator from the left side, resulting in chirality. The coupling strength between system modes can be precisely controlled by adjusting the detuning amount of the atomic pump field. Because of the splitting of the resonant frequency generated by the Fizeau drag, the destructive quantum interference generated in right side drive prevents the nonresonant transition path of state |1,0⟩ to state |2,0⟩. This direction-dependent chiral quantum optics is expected to be applied to chiral optical devices, single-photon sources and nonreciprocal quantum communications.     

Amplification of noise in the quantum theory of parametric processes

A quantum mechanical treatment is given of the acousto-optical parametric amplification processes in dielectric crystals when the signal acoustical and idler light waves are amplified in the presence of intensive optical pumping. The approximate Heisenberg equations of motion are found and solved for the creation and annihilation operators of signal and idler modes with due regard for the interaction of these modes with other light and vibratory modes of the crystal (“the thermostat”). It is shown that the thermostat influence results in noise and attenuation effects. These persistent noises are also amplified. If the pumping is not far above the threshold the persistent noises are more important than the initial ones.     

Generation of phase-correlated light pulses in a hyper-Raman active medium

We analysis within the quantum setting the effect of correlation of monochromatic fields of the Stokes and parametric radiation generated in a two-photon-absorbing medium by hyper-Raman scattering and four-wave mixing, respectively. Our results show that when there is destructive interference between the two processes, both modes are amplified in the medium in a correlated way, so that beyond a certain characteristic distance they propagate in a stationary manner with the same amplitudes and photon statistics but with opposite phases, while the medium becomes transparent to them. We calculate the intensity of the fields, the emission linewidths, and the diffusion of the total phase, the latter determining the extent of phase noise correlation at the output. We also show that no matter how the phases of the separate modes diffuse, the quantum fluctuations in the total phase may be completely squeezed. Zh. éksp. Teor. Fiz. 111, 1942–1954 (June 1997)     

Pulse Transmission and State Conversion in Two-mode Optomechanical Cavity Coupled with Atomic Medium

We investigate the quantum state conversion between cavity modes of distinctively different wavelengths for the two-mode optomechanical cavity coupled with the three-level lambda atom. In the frequency domain, we show that the coherence of atom medium leads to the two maximum transmissions. We also show that the injected atom can interrupt the traveling photon pulses which is transmitted between the different input and output channels. Thus, the addition of atom provides us a way to control the transmission between the quantum states of two cavity modes and the photon information storage.     

Dicke quantum spin glass of atoms and photons

Recent studies of strongly interacting atoms and photons in optical cavities have rekindled interest in the Dicke model of atomic qubits coupled to discrete photon cavity modes. We study the multimode Dicke model with variable atom-photon couplings. We argue that a quantum spin-glass phase can appear, with a random linear combination of the cavity modes superradiant. We compute atomic and photon spectral response functions across this quantum phase transition, both of which should be accessible in experiments.     

Continuous variable entanglement generation in coupled cavities

We investigate continuous variable entanglement produced in two distant coupled cavities, in which two four-level atoms are driven by classical fields respectively. Under the large detuning condition, an effective Hamiltonian containing the square of the creation (annihilation) operator of the cavity field is derived. Due to the nonlinearity, entanglement formally created by the beam splitter type interaction is transformed into the nondegenerate parametric down conversion type. Employing the operator algebraic method, we study the time evolution of the entanglement condition, and show that the system provides us an advantage in achieving a larger photon number with better entanglement. We also discuss the dissipation of the cavities affecting the entanglement.     

Dynamics for a two-atom two-mode intensity-dependent Raman coupled model

We study the quantum dynamics of a two-atom Raman coupled model interacting with a quantized bimodal field with intensity-dependent coupling terms in a lossless cavity. The unitary transformation method used to solve the time-dependent problem also gives the eigensolutions of the interaction Hamiltonian. We study the atomic-population dynamics and dynamics of the photon statistics in the two cavity modes, and present evidence of cooperative effects in the production of antibunching and anticorrelations between the modes. We also investigate the effect of detuning on the evolution of second-order correlation functions and observe that the oscillations become more rapid for large detuning.