Coherent repopulation of the components of a three-level quantum system in the field of a pulsed bichromatic radio frequency wave

The coherent repopulation of a quantum system consisting of three nonequidistant levels in the field of a resonant bichromatic rf wave is studied. The atoms are assumed to have an impulsive interaction with the rf wave in which the pulse duration is less than any of the relaxation times. The hyperfine structure of gas atoms and a system of atomic oscillator levels in a magnetic trap are considered as examples of such a quantum system. It is shown that in the second case, the coherent repopulation effect can be used to cool neutral atoms in magnetic traps. Zh. éksp. Teor. Fiz. 113, 1181–1192 (April 1998)     

射频驱动精细结构能级跃迁引起的非线性效应

研究了射频驱动精细结构能级跃迁引起的电磁诱导透明(EIT)和电磁诱导吸收(EIA)的转化.通过采用射频场同时驱动激发态和基态精细结构能级跃迁,使系统中出现EIT和EIA.研究结果表明,调谐射频场频率从与基态精细结构能级共振到与激发态精细结构能级共振的过程中,EIT和EIA相互转化,而且射频场的拉比频率取值不同,EIT和EIA的变化规律也不同.     

射频驱动精细结构能级跃迁引起的非线性效应

研究了射频驱动精细结构能级跃迁引起的电磁诱导透明（EIT）和电磁诱导吸收（EIA）的转化。通过采用射频场同时驱动激发态和基态精细结构能级跃迁,使系统中出现EIT和EIA。研究结果表明,调谐射频场频率从与基态精细结构能级共振到与激发态精细结构能级共振的过程中,EIT和EIA相互转化,而且射频场的拉比频率取值不同,EIT和EIA的变化规律也不同。     

Multiplication of qubits in a doubly resonant bichromatic field

Multiplication of spin qubits arises at double resonance in a bichromatic field when the frequency of the radio-frequency (rf) field is close to that of the Rabi oscillation in the microwave field, provided its frequency equals the Larmor frequency of the initial qubit. We show that the operational multiphoton transitions of dressed qubits can be selected by the choice of both the rotating frame and the rf phase. In order to enhance the precision of dressed qubit operations in the strong-field regime, the counter-rotating component of the rf field is taken into account.     

Coherent hole-burnings induced by a bichromatic laser field

In a Doppler-broadened three-level Λ-type system driven simultaneously by a coupling laser and two equal-amplitude saturating laser fields with a frequency difference 2δ, the absorption spectrum of a weak probe laser exhibits multiple deep spectral holes through coherent hole-burning CHB with controllable numbers, widths, depths, and positions. More significant, changing δ or lasers directions, CHBs can degenerate into narrower and deeper spectral holes where the slope of the refractive index is very steep. The multiple narrow spectral holes in a single absorption profile are expected to have potential applications in high density storage, optical information processes, and slow-light.     

Modified stimulated photon echo with hyperfine structure of resonant levels

The intensity and polarization of a modified stimulated photon echo generated on resonant levels with hyperfine structure are obtained. It is proposed that the polarization properties of this kind of a photon echo can be used for the identification of the structure of the resonant transitions on which the echo is formed as well as for the separation of the modified stimulated photon echo pulse from the third exciting pulse.     

超精细结构对激光与二能级原子相互作用的影响

应用半经典理论建立了一个简化模型,对157Gd原子在激光作用下17795267cm-1(9D3)←→532977cm-1(9D4)的能级跃迁进行计算并给出了计算结果,提出相应的理论解释,分析了超精细结构对激光与二能级原子相互作用的影响 关键词： 超精细结构 原子蒸气激光同位素分离 二能级原子 钆原子     

对称强双色共振场中弛豫效应对二能级系统斯塔克分裂的影响

本文应用半径典理论、密度矩阵方法和探索场中二能级系统的能级斯塔克(Stark)分裂。指出与无弛豫效应相比较,弛予效应不仅改变了由光学斯塔克效应所产生的分裂能级的权重、展宽了这些能级,而且还出现新的分裂能级。     

Electron-positron pair formation in the field of a bichromatic plane electromagnetic wave

On the basis of the accurate solution of the Dirac equation for an electron in the field of a bichromatic plane wave consisting of two monochromatic waves propagating in the same direction, the probability of formation of an e⁺e^– pair by a quantum in the wave field is calculated. The cases of small and large intensities of the wave components are considered, together with the transition in the limit to a constant field.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 46–53, February, 1977.The authors thank A. A. Sokolov for his constant interest in the work and discussion of the results.     

Coherent phase control in electron argon scattering in a bichromatic laser field

This paper theoretically investigates the coherent phase control in electron--argon scattering assisted by a bichromatic laser field. The laser field is composed of a fundamental component and its second harmonic. The incoming and out going states of electron are described by the Volkov wave functions, and the electron--target interaction is treated as a screening potential. Numerical results for differential cross section of multiphoton processes vs the phase difference between the two components of laser field are discussed for several scattering angles and impact energies.     

Coherent forward scattering of a single photon wave packet in a resonant medium

The propagation of a single photon wave packet in a thick resonant medium was studied theoretically and experimentally. The well-known acceleration of wave packet decay was observed upon wave packet exiting from a medium with single resonant absorption line. It was found that in a medium with two closely spaced absorption lines, the restoration of the photon wave packet is observed after the acceleration of decay.     

Production of electron-positron pairs on nuclei in the field of a bichromatic plane electromagnetic wave

The exact solution of the Dirac equation for an electron in the field of a bichromatic plane electromagnetic wave — with components that are monochromatic waves propagating in one direction — is used to calculate the probability of e⁺e^– pair production on a nucleus in the field of such a wave. This influence of the nucleus is treated perturbatively as an external Coulomb field. The cases of small and large values of the intensity parameters of the wave components are considered and the passage to the limit of a crossed field is discussed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 33–40, September, 1978.We are very grateful to V. R. Khalilov for a fruitful discussion of the results.     

Coherent resonant scattering of nuclear radiation in a paramagnetic absorber placed in a magnetic field

When a thick Mössbauer absorber of (paramagnetic) ferric alum enriched in⁵⁷Fe is placed in a longitudinal magnetic field of 270 G, a reduction of the intensity of backscattered resonant radiation from a⁵⁷CORh is observed. This is interpreted as caused by an increase of the degree of coherence of the resonant radiation re-emitted by the absorber. Further experiments are needed to corroborate this interpretation.     

Kinetics of atoms in a bichromatic field

The kinetics of atoms in a bichromatic field is considered. Analytic solutions are obtained for the force, friction coefficient, and diffusion coefficient in the model of a two-level atom without limitations imposed on the intensity of light fields. This effect is observed in the domain of global minima and maxima of the optical potential (i.e., at points where the relative phase of two standing waves is ? = 0, π/2.     

Diffraction pattern of atoms in a resonant standing wave laser field

We illustrate the diffraction pattern of an atomic beam for a resonant standing wave laser field, and stress its dependence on the angle of incidence. A maximum spread of the atomic beam is found to occur for an incidence angle close to, but different from normal incidence.     

Deflection of resonant multilevel particles in a standing wave light field

We study the deflection of an atomic system with a resonant multilevel energy structure in classical and quantized wave light fields. We obtain that the shape of the momentum distribution is very sensitive to the energy level structure, whereas its moments are not. Comparison with a two-level case is made.     

Coherent resonant transport through a mesoscopic system with quantum ac microwave field

The time-dependent transport through an ultrasmall quantum dot coupling to two electron reservoirs is investigated. The quantum dot is perturbed by a quantum microwave field (QMF) through gate. The tunneling current formulae are obtained by taking expectation values over coherent state (CS), and SU(1,1) CS. We derive the transport formulae at low temperature by employing the nonequilibrium Green function technique. The currents exhibit coherent behaviors which are strongly associated with the applied QMF. The time-dependent currents appear compound effects of resonant tunneling and time-oscillating evolution. The time-averaged current and differential conductance are calculated, which manifest photon-assisted behaviors. Numerical calculations reveal the similar properties as those in classical microwave field (CMF) perturbed system for the situations concerning CS and squeezed vacuum SU(1,1) CS. But for other squeezed SU(1,1) CS, the tunneling behavior is quite different from the system perturbed by a single CMF through gate. Due to the quantum signal perturbation, the measurable quantities fluctuate fiercely. Received 28 May 1998     

Atom in a femtosecond bichromatic laser field

The ionization of real hydrogen atom is studied under the action of a two-color pulsed laser field of duration 2.12 fs consisting of a fundamental frequencyω and one of its harmonics. We study the effect of phase difference (φ betweenω and its harmonic on the ionization probability. It is found that ionization can be switched on and off by varying the relative phaseφ betweenω and its harmonic.