Effect of thermal excitations of the reservoir on phase bistability in the fundamental model of quantum optics

The effect of the finite temperature of the reservoir on the phase bistability in the fundamental model of quantum optics is studied based on the Q distribution function calculated numerically and on the P distribution function obtained analytically in the case of large Rabi frequencies. The condition for the appearance of the phase bistability in a system with allowance for thermal excitations of the reservoir is obtained.     

Nonlinear optics and quantum entanglement of ultraslow single photons

Two light pulses propagating with slow group velocities in a coherently prepared atomic gas exhibit dissipation-free nonlinear coupling of an unprecedented strength. This enables a single-photon pulse to coherently control or manipulate the quantum state of the other. Processes of this kind result in generation of entangled states of radiation field and open up new prospectives for quantum information processing.     

Nonlinear quantum optics in a waveguide: distinct single photons strongly interacting at the single atom level

We propose a waveguide-QED system where two single photons of distinct frequency or polarization interact strongly. The system consists of a single ladder-type three level atom coupled to a waveguide. When both optical transitions are coupled strongly to the waveguide's mode, we show that a control photon tuned to the upper transition induces a π phase shift and tunneling of a probe photon tuned to the otherwise reflective lower transition. Furthermore, the system exhibits single photon scattering by a classical control beam. Waveguide-QED schemes could be an alternative to high quality cavities or dense atomic ensembles in quantum information processing.     

Magneto optics of single photons emitted from single InAs/GaAs self-assembled quantum dots in a planar microcavity

We fully characterize the fine spectral structure of neutral and negatively charged single microcavity quantum dot excitons, using polarization-sensitive magneto-photoluminescence spectroscopy. We show that the microcavity allows the simultaneous detection of both the bright and dark excitons using Faraday configuration. Thus, we were able to fully determine the fine structure and the g-factors of the neutral and negatively charged single exciton states within the same single quantum dot. Our measurements are in excellent agreement with novel, many carrier model calculations, which take into account Coulomb and exchange interactions among all the confined e–h pair states.     

Symmetry approach to the analysis of coherent structures in quantum optics: Foundations and examples

A general symmetry method for the discovery and analysis of hidden coherent structures in quantum models with an invariant Hamiltonian is proposed. The method is based on the mathematical concept of dual algebraic pairs, which unifies the actions of invariance groups and algebras of dynamic symmetry. Its efficiency is illustrated by the examples of biphotons and the invariant treatment of unpolarized light quasi-spin clusters, and “optical atoms” in nonlinear quantum-optical models.     

Voltage-controlled optics of a quantum dot

We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. We find that the transmission spectrum of the neutral exciton exhibits two narrow lines with approximately 2 mueV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. The exchange interaction can be turned off by choosing a gate voltage where the dot is occupied with an additional electron. Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system. Our experiments show that the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a mueV energy scale.     

大气闪烁对纠缠相干态量子干涉雷达影响机理

介绍了量子干涉雷达物理模型及其探测原理,并采用耗散-涨落通道处理量子光场在湍流大气中的传输,从经典湍流统计理论推导得到大气透射率的概率密度分布函数P(T),以此为基础系统分析了大气闪烁效应对纠缠相干态量子干涉雷达的影响机理,深入讨论了平均大气透射率、闪烁指数等大气参数对系统目标探测性能的影响.研究发现:低损耗情况下系统灵敏度及分辨率性能随闪烁指数的增加而降低;高损耗情况下大气闪烁则能显著提高系统灵敏度和分辨率性能,且界定高低损耗的透射率临界点随脉冲光子数增加而增加,故大气闪烁能够在一定程度上克服大气损耗造成的不良影响.     

Hard X-ray optics simulation using the coherent mode decomposition of the Gaussian Schell model

The propagation of a hard X-ray beam from a partially coherent synchrotron source is simulated by using the novel method based on the coherent mode decomposition of Gaussian Schell model and wave-front propagation. We investigate how the coherency properties and intensity distributions of the beam are changed by propagation through optical elements. Here, we simulate and analyze the propagation of the partially coherent radiation trans- mitted through an ideal slit. We present the first simulations for focusing partially coherent synchrotron hard X-ray beams using this novel method. And when compared with the traditional method which assumes the source is a totally coherent point source or completely incoherent, this method is proved to be more reasonable and can also demonstrate the coherence properties of the focusing beam. We also simulate the Young’s double slit experiment and the simulated results validate the academic analysis.     

Collective atomic recoil lasing with a partially coherent pump

We investigate the effect of pump phase noise on the collective backscattering of light by a cold, collisionless atomic gas. We show that for a partially coherent pump field, the growth rate of the backscattered field is reduced relative to that for a coherent pump, but the backscattered intensity can be increased. Our results demonstrate that fluctuations and noise can play a counterintuitive role in nonlocally coupled many-body systems.     

The Coulomb solution as a coherent state of unphysical photons

In the context of the problem of what micro-states are responsible for the entropy of black holes, we consider as a physical toy model the electromagnetic Coulomb solution. By quantizing the electromagnetic field in the presence of an external source of charge Q, the quantum state corresponding to the Coulomb solution is identified as a coherent state of longitudinal and temporal photons in a Hilbert space with negative norm states.     

Leggett-Garg inequality with a kicked quantum pump

A kicked quantum nondemolition measurement is introduced, where a qubit is weakly measured by pumping current. Measurement statistics are derived for weak measurements combined with single-qubit unitary operations. These results are applied to violate a generalization of the Leggett-Garg inequality. The violation is related to the failure of the noninvasive detector assumption, and may be interpreted as either intrinsic detector backaction, or the qubit entangling the microscopic detector excitations. The results are discussed in terms of a quantum point contact kicked by a pulse generator, measuring a double quantum dot.     

在Jaynes-Cumming模型中相干态的相位对量子相干性的影响

基于J-C模型,研究了相干迭加光场与二能级原子相互作用时的量子动力学行为,讨论了迭加态的相位对原子的量子崩塌-回复特性的影响.     

Thermal optics distortion of face pump slab lasers with two pump arrangements

Two pump arrangements, which are the slow axis and the fast axis of LD stacks parallel to the length direction of the slab, are simulated. From the results the optical intensity along the width of the slab is Gaussian and super-Gaussian distribution, respectively. Then based on heat conduction equation and conductively cooling boundary condition, the calculation of the distribution of absorbed pump power, temperature and thermal stress with the tool of finite element analyses is performed. From these results we numerically calculate the thermal focusing in zigzag and perpendicular zigzag planes using the ray tracing method running at low and high repetition rates. It is found that the temperature distribution along width has a significant impact on the thermal stress and thermal optics distortion, especially running at high repetition rate or high average power. Finally, the conclusion was that the pump arrangement with the fast axis of LD stacks parallel to the length direction of the slab is superior to the slow axis of LD stacks parallel to the length direction of the slab in decreasing thermal lens effect and obtaining high beam quality.