Quasiresonance interaction between a multiphoton field and a material

It is shown that the number of branches in the energy spectrum of a multiphoton field in a dispersive medium increases together with the number of photons. The kinetics of an individual quantum cannot be considered independently of the evolution of the field as a whole, even if the interaction between the field and each molecule of the medium is linear. The probabilities of the processes which accompany the transition of a quantum from one branch of the spectrum to another are calculated.     

Decoherence of the field in quantum nondemolition photon number measurement using the Kerr nonlinearity

The role of decoherence of an electromagnetic field in the process of quantum nondemolition measurement of the number of photons using a nonlinear Mach-Zehnder interferometer is investigated. This decoherence is caused by distributed losses in a Kerr medium. A long interaction time between the field and the medium is required to achieve a high accuracy in the photon number measurement. The losses in the Kerr medium accompanying the resonance four-wave interaction between the measured and the probe fields lead to a measurement error close to unity at γτ ?1 (γ is the rate of losses in the medium, and τ is the time of interaction between the field and the medium); consequently, nondemolition quantum measurement turns out to be impossible in the scheme considered. Under these conditions, an increase in the intensity of the probe field does not result in achievement of the required measurement accuracy.     

Kerr介质腔中“单模光场-V型三能级原子系统”的场熵演化特性

利用全量子理论,研究了附加Kerr介质腔中“V”型三能级原子与单模相干态光场相互作用的场熵演化规律,讨论了Kerr效应和初始场的平均光子数n(初始场强)对场熵演化的影响.     

Quantum Entanglement in Two-Photon Tavis–Cummings Model with a Kerr Nonlinearity

The properties of quantum entanglement in the two-photon Tavis–Cummings model with a Kerr nonlinearity are studied in terms of quantum information entropy theory. The reduced quantum entropy is employed to investigate the quantum entanglement between two two-level atoms and a single-mode coherent field. The relative quantum entropy is employed to investigate the quantum entanglement between the two two-level atoms. The influences of the nonlinear interaction of the Kerr medium with the field and the atomic dipole-dipole interaction on the properties of quantum entanglement of the system are also examined. Some important results are obtained.     

受激拉曼增益介质中的量子噪声特性研究

研究了三能级原子系综与相干控制场以及量子探测场的相互作用下的受激拉曼系统.运用量子理论推导出了该受激拉曼系统中由于量子场真空涨落引起的量子噪声以及受激散射的量子化光场噪声谱,并且数值计算了注入拥有非经典涨落的量子探测场,真空涨落所引起的量子噪声谱. 关键词： 受激拉曼增益 量子噪声 噪声谱     

Dynamics of formation of superposition states of light in an absorbing medium

The process of simultaneous absorption of two photons in a medium in the presence of a weak one-photon absorption is considered. The medium is perturbed from outside in a two-photon parametric manner. The formation of a stationary even-parity superposition state of light in such a medium is shown to be possible in the region of small amplitudes of the state (weak perturbations of the system). This is associated with the fact that, in this region of interaction, the field spends considerably more time in the even superposition state than in the odd state. It is shown that a nonstationary superposition state of light with a large amplitude of the state (large photon numbers) can be obtained for interaction times that are longer than the most probable time of the first two-photon quantum jump of the field state and shorter than the most probable time of the first one-photon jump of the field state. The dynamics of formation of the quantum entropy of the field is studied by numerical simulation of quantum trajectories of the system. The Wigner functions of the state of the field are calculated. Analytical results are obtained for the density matrix of the stationary state of the system in the presence of a weak one-photon absorption.     

Detecting a single atom in a cavity using the χ(2) nonlinear medium

We propose a protocol for detecting a single atom in a cavity with the help of the χ⁽²⁾ nonlinear medium. When the χ⁽²⁾ nonlinear medium is driven by an external laser field, the cavity mode will be squeezed, and thus one can obtain an exponentially enhanced light-matter coupling. Such a strong coupling between the atom and the cavity field can significantly change the output photon flux, the quantum fluctuations, the quantum statistical property, and the photon number distributions of the cavity field. This provides practical strategies to determine the presence or absence of an atom in a cavity. The proposed protocol exhibits some advantages, such as controllable squeezing strength and exponential increase of atom-cavity coupling strength, which make the experimental phenomenon more obvious. We hope that this protocol can supplement the existing intracavity single-atom detection protocols and provide a promise for quantum sensing in different quantum systems.     

Fidelity of quantum information for V-type three-level atom interacting with a number state light field in Kerr medium

In this paper the evolution characteristics of the fidelity of quantum information for the V-type three-level atom interacting with number state light field in Kerr meddium are investigated. It shows that the periodicity of the evolutions of fidelity of quantum information is influenced by the Kerr coefficient, the photon number of the initial field and intensity of light. The evolutions of the fidelity of quantum information are modulated by the initial number state field. The Rabi oscillation frequency and the modulation frequency of fidelity for the field and the system vary with the value of the Kerr coefficient. The evolutions of fidelity of quantum information obviously show the quantum collapse and revival behaviours in the system of atom interacting with light field.     

Evolution of the Photon-number Probability Distribution in the System of a Three Level Atom with an Added Kerr-like Medium

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克尔介质中"耦合双原子-场"模型的光场压缩效应

利用全量子理论，研究克尔介质中耦合二能级双原子与场相互作用的压缩效应，着重讨论了克尔介质对光场压缩效应的影响，并揭示了初始场强及原子间耦合系数的变化与光场压缩效应的关系。     

Quantum memory on the basis of photon echo in three-level optically dense gaseous media with the Ξ-configuration of atomic transitions

A new variant of realization of quantum memory based on the use of a photon echo in an optically dense three-level gaseous medium is proposed. The use of a long-lived highly excited optical level as a storage of quantum information is the characteristic feature of the scheme proposed. This scheme of quantum memory is distinguished by reduced optical noises owing to the possibility of realizing temporal, spectral, and spatial selection of weak quantum radiation relative to the accompanying laser pulsed fields.     

类科尔介质中受激辐射场的量子统计性质

本文讨论类科尔介质腔中场模与三能级原子相互作用时辐射场的量子统计性质。结果表明,介质与场模的相互作用使场模与原子的相互作用减弱,光子一般不表现反聚束性质,辐射场服从超亚泊松统计分布。     

Anisotropic distribution of quantum‐vacuum momentum density in a moving electromagnetic medium

An isotropic electromagnetic medium becomes gyrotropically anisotropic when it moves, and an anisotropic electromagnetic environment can then be created in this motion‐induced anisotropic medium. One of the most remarkable features is that the quantum vacuum in the anisotropic electromagnetic environment exhibits a nonzero electromagnetic momentum density, since the universal symmetry of the vacuum fluctuation field is broken, and the anisotropic quantum vacuum mode structure is produced because of the symmetry breaking. This would give rise to a noncompensation effect among the four vacuum eigenmodes (i.e., the forward and backward propagating modes as well as their respective mutually perpendicular polarized components), and leads to an anisotropic correction to the vacuum momentum in the moving medium. The physical significance and the potential applications of the anisotropic quantum vacuum are discussed. This quantum‐vacuum effect may be used to develop sensitive sensor techniques and to design new quantum optical and photonic devices.     

Magnetic field effects on the quantum wire energy spectrum and Green's function

We analyze the energy spectrum and propagation of electrons in a quantum wire on a 2D host medium in a normal magnetic field, representing the wire by a 1D Dirac delta function potential which would support just a single subband state in the absence of the magnetic field. The associated Schrödinger Green's function for the quantum wire is derived in closed form in terms of known functions and the Landau quantized subband energy spectrum is examined.     

Formation of nonclassical states of light in media with a three-photon resonance

The process of simultaneous absorption of three photons in a medium subjected to a three-photon parametric perturbation is considered. It is shown that in such a medium one can observe the formation of the radiation field states, which are the quantum superposition of three coherent components. One-photon and twophoton absorption processes in the medium also destroy the interference between the components of the superposition state. The states being formed are investigated in both the temporal development (numerically) and the stationary limit (numerically and analytically); the Wigner functions, as well as the quantum entropy, are calculated for a whole series of initial states. It is shown that depending on the initial state of the radiation field, the interference between the three-component superposition states being formed can lead, for example, to the almost total localization of the system in a two-component state or to the destruction of the interference between different coherent components.     

高Q Kerr介质腔中二项式光场与原子相互作用

应用全量子理论研究了在高Q Kerr介质腔中, 二能级原子与二项式光场相互作用系统中原子行为和光场的量子特性. 采用数值计算的方法, 详细讨论了光场参量和Kerr效应对原子布居反转和平均光子数的影响.研究发现当二项式光场处在中间态时, 在考虑Kerr效应的条件下,原子布居振荡加剧, 回复时间变短, 系统内平均光子数减少.     

虚光场对克尔介质中受激原子统计性质的影响

研究了类克尔介质中虚光场效应对受激三能级了的光子统计演化性质的影响。结果表明：虚光场效应导致了受激辐射场的光子统计演化中出现的量子噪声,量子噪声随光场频率的增大而减小,当增大到一定值时,量子噪声几乎消失,原子－场耦合系数的增加使光子统计演化的拉比振荡的振幅加大、频率变快;而介质－场耦合系数的增加使光子统计演化拉比振荡的振幅变小、频率变慢。     

Properties of strong-coupling magneto-bipolaron qubit in quantum dot under magnetic field

Based on the variational method of Pekar type, we study the energies and the wave-functions of the ground and the first-excited states of magneto-bipolaron, which is strongly coupled to the LO phonon in a parabolic potential quantum dot under an applied magnetic field, thus built up a quantum dot magneto-bipolaron qubit. The results show that the oscillation period of the probability density of the two electrons in the qubit decreases with increasing electron–phonon coupling strength α, resonant frequency of the magnetic field ω_c, confinement strength of the quantum dot ω_0, and dielectric constant ratio of the medium η; the probability density of the two electrons in the qubit oscillates periodically with increasing time t, angular coordinate φ_2, and dielectric constant ratio of the medium η; the probability of electron appearing near the center of the quantum dot is larger, and the probability of electron appearing away from the center of the quantum dot is much smaller.     

高Q克尔介质腔中依赖强度耦合的J-C模型中光场相位特性

应用Pegg-Barnett相位理论研究了被克尔介质包围的依赖强度耦合的J-C模型中光场相位演化特性, 结果发现, 原子-光场的耦合常数和克尔介质-光场的耦合常数将导致相位的涨落明显增大, 在原子初始处于非相干性激发时光场的频率也会发生漂移