Intensity Correlation of the Resonance Fluorescence Light in Quasi-monochromatic Chaotic Fields

The behaviour of the intensity correlation function of the resonance fluorescence light from a single atom is studied in the case of a quasi-monochromatic chaotic pump field of arbitrary mean intensity. In particular, it is found that the factorization of the intensity correlation function, which is impossible in the case of a narrow band chaotic pump field of low intensity, becomes a better approximation when the mean intensity of the pump field is enhanced.     

Intensity correlation of the resonance fluorescence radiation from an atom driven by a laser pump with amplitude and phase fluctuations

The influence of the phase and amplitude fluctuations of a relatively weak laser pump on the intensity correlations of the resonance fluorescence light from a single atom is studied. It is found that the contributions due to a non-Markovian dephasing of the laser light can be neglected in many cases. The amplitude fluctuations and the attendant non-factorizability of the intensity correlation function are shown to lead to a stronger correlation of the intensities of the resonance fluorescence light considered.     

Cavity QED with quantized center of mass motion

We investigate the quantum fluctuations of a single atom in a weakly driven cavity, where the center of mass motion of the atom is quantized in one dimension. We present analytic results for the second order intensity correlation function g((2))(tau) and the intensity-field correlation function h(theta)(tau), for transmitted light in the weak driving field limit. We find that the coupling of the center of mass motion to the intracavity field mode can be deleterious to nonclassical effects in photon statistics and field-intensity correlations, and compare the use of trapped atoms in a cavity to atomic beams.     

Real-space observation of current-driven domain wall motion in submicron magnetic wires

We report direct observation of current-driven magnetic domain wall (DW) displacement by using a well-defined single DW in a microfabricated magnetic wire with submicron width. Magnetic force microscopy visualizes that a single DW introduced in a wire is displaced back and forth by positive and negative pulsed current, respectively. The direct observation gives quantitative information on the DW displacement as a function of the intensity and the duration of the pulsed current. The result is discussed in terms of the spin-transfer mechanism.     

Intensity correlations in resonance fluorescence from two atoms

The intensity correlation function of resonance fluorescence radiation from a two atom system is calculated in the weak-field limit.     

Intensity correlation of fluorescence radiation from impurity atoms in solids in the low temperature limit

The influence of the linear electron-photon coupling on the intensity correlation function of the resonance fluorescence light from an impurity atom in a solid is studied. It is found that this coupling can lead to a stronger anticorrelation of the emitted photons in comparison with the case of a free atom.     

The effect of localization on interference. I. Calculated intensities for a feasible optical experiment

A simple geometry utilizing a laser-excited atomic beam as light source, and a nearby oscillating mirror, would permit the observation of a two-channel optical interference effect involving photons which can be localized predominantly in one channel by coincidence observations of the recoiling source atom. A sacrifice of the optimum conditions for photon interference is necessary even when photon localization in one channel is accomplished by an observation of the recoil atom. This necessity arises because the width of the slit defining the atomic beam, and with it the important optical source dimension, must be comparable to the optical wavelength to obtain the small uncertainty in initial total momentum needed for significant localization. Quantum mechanical calculations of the coincidence intensity and singles intensity as a function of mirror position are made for a source width of five quarter wavelengths and are compared to a classical optics calculation of the singles intensity. The coincidence intensity calculation, as expected, predicts a smaller interference effect than classical optics due to the photon localization. The singles intensity calculation also predicts the same reduction in the classical interference effect, as a consequence of the orthoganality of the final atom states.     

双模压缩场与V型原子相互作用光场的性质

研究了双模压缩真空场与V型三能级运动原子的相互作用,得到光场二阶相干度和模间相干度的解析表达式;通过数值计算分析了原子运动速度、场模结构参数和平均光子数对光场二阶相干度和模间相干度的影响.结果表明:平均光子数的增加使得二阶相干度和模间相干度显著增大;而原子运动速度、模场结构参数的增加虽然对光子聚束效应和反聚束效应的强度影响不大,却使其演化周期大大减小.     

多光子J-C模型中频率随时间变化场的反聚束效应

利用多光子J-C模型,考虑场频率随时间以正弦函数形式作小量变化,在旋波近似下,研究了二能级原子通过多光子跃迁与单模辐射场相互作用系统中场的反聚束效应.利用数值计算方法给出反映场反聚束效应的二阶关联函数随时间的演化曲线.研究结果表明:场二阶关联函数的演化受场频率随时间正弦函数形式变化的调制,场频率振荡的幅值 u越大调制作用越强,在场频率振荡的幅值u大于一定值后,场二阶关联函数随时间的演化呈现出周期性振荡特性,其振荡周期与场频率变化的周期一致.     

Correlations and counting statistics of an atom laser

We demonstrate time-resolved counting of single atoms extracted from a weakly interacting Bose-Einstein condensate of 87Rb atoms. The atoms are detected with a high-finesse optical cavity and single atom transits are identified. An atom laser beam is formed by continuously output coupling atoms from the Bose-Einstein condensate. We investigate the full counting statistics of this beam and measure its second order correlation function g((2))(tau) in a Hanbury Brown-Twiss type experiment. For the monoenergetic atom laser we observe a constant correlation function g((2))(tau)=1.00 +/- 0.01 and an atom number distribution close to a Poissonian statistics. A pseudothermal atomic beam shows a bunching behavior and a Bose distributed counting statistics.     

Quantum trajectory perspective of atom–field interaction in attosecond time scale

The ionization and high-harmonic generation in hydrogen and helium by using quantum (hydrodynamic) trajectories is analyzed theoretically. The quantum trajectories are introduced in the frame of a new time-dependent quantum Monte Carlo technique that allows a self-contained ab initio treatment of the electron correlation effects without introducing parametrized correlation potentials into the Schrödinger equation. Our approach predicts correct ionization, high-harmonic spectra, and attosecond pulses generated by a helium atom beyond the single active electron approximation. It can be used to study complex multi-electron systems in arbitrary dimensions and their interaction with laser fields of both low and high intensity.     

Extending the trapping lifetime of single atom in a microscopic far-off-resonance optical dipole trap

In our experiment, a single cesium atom prepared in a large-magnetic-gradient magneto–optical trap (MOT) can be efficiently transferred into a 1064-nm far-off-resonance microscopic optical dipole trap (FORT). The efficient transfer of the single atom between the two traps is used to determine the trapping lifetime and the effective temperature of the single atom in FORT. The typical trapping lifetime has been improved from ～ 6.9 s to ～ 130 s by decreasing the background pressure from ～ 1 × 10^–10 Torr to ～ 2 × 10^–11Torr and applying one-shot 10-ms laser cooling phase. We also theoretically investigate the dependence of trapping lifetimes of a single atom in a FORT on trap parameters based on the FORT beam’s intensity noise induced heating. Numerical simulations show that the heating depends on the FORT beam’s waist size and the trap depth. The trapping time can be predicted based on effective temperature measurement of a single atom in the FORT and the intensity noise spectra of the FORT beam. These experimental results are found to be in agreement with the predictions of the heating model.     

Single atom as a mirror of an optical cavity

By tightly focusing a laser field onto a single cold ion trapped in front of a far-distant dielectric mirror, we could observe a quantum electrodynamic effect whereby the ion behaves as the optical mirror of a Fabry-Pérot cavity. We show that the amplitude of the laser field is significantly altered due to a modification of the electromagnetic mode structure around the atom in a novel regime in which the laser intensity is already changed by the atom alone. We propose a direct application of this system as a quantum memory for single photons.     

类Kerr介质中双模SU(1,1)相干态场与Λ型三能级原子相互作用的量子统计性质

导出了类Kerr介质中双模SU(1,1)相干态场与Λ型三能级原子相互作用系统的态函数,研究了Kerr效应对Λ型三能级原子布居概率、双模SU(1,1)相干态场的互关联函数、Cauchy-Schwartz不等式及二阶相干度的影响.结果表明:Kerr效应使原子与光场的耦合减弱,原子布居的崩塌与复苏的周期缩短;在初始光场较弱和较强两种情况下,类Kerr介质对双模SU(1,1)相干态场两模间的相关性、相关程度以及光子的聚束与反聚束效应产生的作用有明显的区别.     

Trapping and observing single atoms in a blue-detuned intracavity dipole trap

A single atom strongly coupled to a cavity mode is stored by three-dimensional confinement in blue-detuned cavity modes of different longitudinal and transverse order. The vanishing light intensity at the trap center reduces the light shift of all atomic energy levels. This is exploited to detect a single atom by means of a dispersive measurement with 95% confidence in 10 micros, limited by the photon-detection efficiency. As the atom switches resonant cavity transmission into cavity reflection, the atom can be detected while scattering about one photon.     

双模压缩真空场与Λ型三能级原子非共振作用

研究了双模压缩真空场与Λ型三能级原子非共振相互作用系统中,场模失谐量对原子布居概率和光场的双模互关联函数、二阶相干度的影响.结果表明：失谐量使原子Rabi振荡呈现周期性崩塌与复苏现象；当光场初始压缩因子r较小时,失谐量将削弱光子的反聚束效应；当r较大时,失谐量又将增强光场两模相关的稳定性.     

Adiabatic approximation of the correlation function in the density-functional treatment of ionization processes

The ionization of a one-dimensional model helium atom in short laser pulses using time-dependent density-functional theory is investigated. We calculate ionization probabilities as a function of laser intensity by approximating the correlation function of the system adiabatically with an explicit dependence on the fractional number of bound electrons. For the correlation potential we take the derivative discontinuity at integer numbers of bound electrons explicitly into account. This approach reproduces ionization probabilities from the solution of the time-dependent Schr?dinger equation, in particular, the so-called knee due to nonsequential ionization.     

Stark shift contribution to field statistics in a generalized Jaynes-Cummings model

The nonlinear and multiphoton interaction between a single two-level atom and two modes of radiation is studied in a generalized Jaynes-Cummings model. An intensity-dependent level shift is considered. The time evolution operator is obtained. The detuning has a photon number dependence. Different statistical aspects pertaining to either the atom or the fields are calculated. The dipole moment, the dipole-dipole correlation function, as well as the transient spectrum are obtained.     

Scattering theory of Kondo mirages and observation of single Kondo atom phase shift

We explain the origin of the Kondo mirage seen in recent quantum corral scanning tunneling microscope experiments with a scattering theory of electrons on the surfaces of metals. Our theory, combined with experimental data, provides a direct observation of a single Kondo atom phase shift. The Kondo mirage observed at the empty focus of an elliptical quantum corral is shown to arise from multiple electron bounces off the corral wall adatoms. We demonstrate our theory with direct quantitive comparison to experimental data.