Solid deuterium clusters provide a new type of target for laser-matter interactions. We present a theory for the generation of laser driven Coulomb explosions that create a hot fusion-producing ion tail. We derive an initial distribution function for the exploded ions, for an arbitrary cluster-size distribution, and solve for the D-D neutron-production rate during the free expansion of these ions into a vacuum. We find good agreement between the theory and the experiment: the theory suggests an explanation for the observed saturation and drop in neutron yield beyond a definite cluster size, consistent with recent experiments by Ditmire [T. Ditmire et al., Nature 398, 489 (1999)] and Zweiback [J. Zweiback et al., Phys. Rev. Lett. 84, 2634 (2000); J. Zweiback et al., Phys. Rev. Lett. 85, 3640 (2000)].

A theory of pump-probe spectroscopy is developed in which optical fields drive two-photon Raman transitions between ground states of an ensemble of three-level atoms. Effects related to the recoil the atoms undergo as a result of their interactions with the fields are fully accounted for in this theory. The linear absorption coefficient of a weak probe field in the presence of two pump fields of arbitrary strength is calculated. For subrecoil cooled atoms, the spectrum consists of eight absorption lines and eight emission lines. In the limit that ${\chi }_1\ll {\chi }_2,$ where ${\chi }_1$ and ${\chi }_2$ are the Rabi frequencies of the two pump fields, one recovers the absorption spectrum for a probe field interacting with an effective two-level atom in the presence of a single pump field. However, when ${\chi }_1\gtrsim {\chi }_2,$ new interference effects arise that allow one to selectively turn on and off some of these recoil-induced resonances.

We have constructed an automated learning apparatus to control quantum systems. By directing intense shaped ultrafast laser pulses into a variety of samples and using a measurement of the system as a feedback signal, we are able to reshape the laser pulses to direct the system into a desired state. The feedback signal is the input to an adaptive learning algorithm. This algorithm programs a computer-controlled, acousto-optic modulator pulse shaper. The learning algorithm generates new shaped laser pulses based on the success of previous pulses in achieving a predetermined goal.

In a wide basis of bound hydrogenic states $(20\mathrm{}<~n<~80,l<~29),$ we simulate redistribution of the initial $50s$ state population by a nonresonant, optical-frequency pulse of the strength at which Rydberg-to-Rydberg Rabi frequencies exceed the pulse frequency. A small transient flow of the population out of the $50l$ manifold $(l=0,1,2,3,\dots )$ is observed and the effect of this $n\ne 50$ redistribution on the formation of the photoionization signal from Rydberg states is calculated in the limit of weak bound-free coupling. This $n\ne 50$ redistribution is found to totally cancel the predictions of the single-n manifold approximation $(n=50\mathrm{}$ in this case) in photoionization.

Effective field theory predicts that the leading nonuniversal effects in the homogeneous Bose gas arise from the effective range for S-wave scattering and from an effective three-body contact interaction. We calculate the leading nonuniversal contributions to the energy density and condensate fraction and compare the predictions with results from diffusion Monte Carlo calculations by Giorgini, Boronat, and Casulleras [Phys. Rev. A 60, 5129 (1999)]. We give a crude determination of the strength of the three-body contact interaction for various model potentials. Accurate determinations could be obtained from diffusion Monte Carlo calculations of the energy density with higher statistics.

We consider the changes in the spectrum of elementary excitations of a flowing superfluid that result when a weak external perturbing potential is added. As a specific application, we study the critical velocity of superfluid flow in a slightly distorted, tight, toroidal trap for atoms. The critical velocity is not accurately predicted by the argument that the flow turns dissipative when the local flow velocity exceeds the local speed of sound somewhere in the fluid. The unusual critical velocity probably reflects the essentially one-dimensional physics of the model.

An atomic multiple-beam interferometer comprised of numerous copropagating stimulated Raman transitions has been developed using laser-cooled and trapped sodium atoms. The interference fringes of the interferometer with multiple rf fields were calculated by a method based on atomic trajectory and were compared with the experimental results. An interference fringe with a finesse of 180 was demonstrated for 200 successive Raman pulses.

We investigate the dynamic stability of two interacting Bose-Einstein condensates moving through each other with a relative velocity $v_r.$ We show that there exists a critical velocity $v_r^{\mathrm{}\left(c\right)\mathrm{}}$ such that for $v_r>v_r^{\mathrm{}\left(c\right)\mathrm{}}$ the condensate mixture becomes unstable. We construct an analytic expression of the critical relative velocity and determine the unstable collective modes. We also discuss how our results can be applied to matter-wave-mixing processes.

The theory of selective reflection from the interface of a dielectric medium and an atomic vapor is reconsidered. Both the local-field correction and the nonexponential decay of the electromagnetic field inside the vapor are accounted for in a purely analytical form. It is shown that the large influence of both effects on the shift of the spectral line is due to an interference between contributions from atoms moving towards the reflecting surface and from those moving away. We show that the local-field correction reduces the blueshift due to the field decay by one-third of its value. A simple formula relating the shift of the maximum of the reflection spectrum to the transition dipole moment and the number density of the atoms is given.

Spectra of the atomic resonance fluorescence and of the cavity-transmitted light in a driven Jaynes-Cummings system are studied theoretically, where the cavity is driven by a classical field of arbitrary strength. In the regime of strong atom-cavity coupling, anomalous resonance peaks occur at $\pm \sqrt{n}{g}^{\prime }\hspace{0.5em}(n=2,3,\dots ),$ with the modified vacuum Rabi frequency $g^{\prime },$ both in the atomic fluorescence and the cavity transmission. These peaks as well as the observed shift of the vacuum Rabi splitting are explained in terms of the quasienergy levels induced dynamically by the strong driving field. For a stronger driving field, it is shown that the spectrum of the cavity transmission deviates from that of the atomic fluorescence. In the presence of significant damping, the spectrum of the cavity transmission approaches a singlet structure in the strong driving-field limit, and it is found additionally that a bimodal photon-number distribution, which results in a unique quintuplet spectrum of the atomic fluorescence, does not show up in the cavity transmission.

We establish a connection between the simple harmonic oscillator and a two-level atom interacting with resonant, quantized cavity and strong driving fields, which suggests an experiment to measure the harmonic-oscillator’s probability distribution function. To achieve this, we calculate the Autler-Townes spectrum by coupling the system to a third level. We find that there are two different regions of the atomic dynamics depending on the ratio of the Rabi frequency ${\Omega }_c$ of the cavity field to that of the Rabi frequency $\Omega$ of the driving field. For ${\Omega }_c<\Omega$ and moderate coupling of the transition to the cavity mode the spectral peaks are composed of multiplets. A quantized dressed-atom approach provides a simple explanation of the spectral features and shows that the oscillations in the spectral components arise from the oscillations of the population distribution in the dressed states. The observation of these features would provide evidence for the quantum nature of the cavity field. The distribution is an analog of the harmonic-oscillator probability distribution function, and should be experimentally observable. For ${\Omega }_c>~\Omega$ there is no Autler-Townes splitting and the spectrum is composed of a single peak located at the frequency of the probe transition. We show that this effect results from the collapse of the atom to the ground state, which has been predicted by Alsing, Cardimona, and Carmichael [Phys. Rev. A 45, 1793 (1992)] for a two-level atom in a lossless cavity.

The quadrupole moment of a hydrogen atom in a magnetic field B for field strengths from 0 to $4.414\times {10}^{13}\hspace{0.5em}\mathrm{G}$ is calculated by two different methods. The first method is variational, and based on a single trial function. The second method deals with a solution of the Schrödinger equation in the form of a linear combination of Landau orbitals.

Partial measurement turns the initial superposition not into a definite outcome but into a greater probability for it. The probability can approach 100%, yet the measurement can undergo complete quantum erasure. In the Einstein-Podolsky-Rosen (EPR) setting, we prove that (i) every partial measurement nonlocally creates the same partial change in the distant particle, and (ii) every erasure inflicts the same erasure on the distant particle’s state. This enables an EPR experiment where the nonlocal effect does not vanish after a single measurement but keeps “traveling” back and forth between particles. We study an experiment in which two distant particles are subjected to interferometry with a partial “which path” measurement. Such a measurement causes a variable amount of correlation between the particles. A new inequality is formulated for same-angle polarizations, extending Bell’s inequality for different angles. The resulting nonlocality proof is highly visualizable, as it rests entirely on the interference effect. Partial measurement also gives rise to a new form of entanglement, where the particles manifest correlations of multiple polarization directions. Another novelty in that the measurement to be erased is fully observable, in contrast to prevailing erasure techniques in which it can never be observed. Some profound conceptual implications of our experiment are briefly pointed out.

We analyze the continuous pumping of atoms into a Bose-Einstein condensate via spontaneous emission from a thermal reservoir of atoms. We consider the case of atoms with a three-level $\Lambda$ scheme, in which one of the atomic transitions has a very much shorter lifetime than the other one. We found that in such a scenario the photon reabsorption in dense clouds at the frequency of the narrow transition can be considered negligible. If, in addition, inelastic processes can be kept negligible, we find that optical pumping can be used to continuously load and refill Bose-Einstein condensates, i.e., it provides a possible way to achieve a continuous atom laser.

The application of x-ray spectroscopy methods enabled a space-resolved observation of the high-energy Rydberg satellite series ${1s2lnl}^{\prime }\to {1s}^{2}2l+h\nu$ and the ${\mathrm{Ly}}_{\beta }$ satellites ${2l3l}^{\prime }\to 1s2l+h\nu$ in dense laser-produced plasmas. Ab initio atomic structure calculations including relativistic and QED effects show excellent agreement with the precise wavelengths measurements. Satellite transitions with $n>\mathrm{}3\mathrm{}$ split into three distinct groups. For $n>\mathrm{}5,$ the transitions are found to merge with the ${\mathrm{Ly}}_{\beta }$ satellite transitions ${2l3l}^{\prime }\to 1s2l+h\nu$ and the series limits approach the ${\mathrm{Ly}}_{\beta }$ line. This leads to emission on the red and even on the blue wing of the ${\mathrm{Ly}}_{\beta }$ line. Spatially and spectrally resolved intensity distribution discovered strong spatial restrictions of the Rydberg satellite intensities near the target surface. On the contrary, all resonance lines show strong emissions up to 10-mm distance from the target and large optical thickness. This enabled us to develop essentially opacity-free and spatially localized temperature diagnostics based on Rydberg satellite emission. Total x-ray emission spectra are established with the help of the MARIA suite of kinetic codes. The derived properties of the spectral distribution make the high-energy Rydberg satellites of general interest for the wide class of dense plasma experiments.

Sufficient conditions for complete controllability of N-level quantum systems subject to a single control pulse that addresses multiple allowed transitions concurrently are established. The results are applied in particular to Morse and harmonic-oscillator systems, as well as some systems with degenerate energy levels. Controllability of these model systems is of special interest since they have many applications in physics, e.g., Morse and harmonic oscillators serve as models for molecular bonds, and the standard control approach of using a sequence of frequency-selective pulses to address a single transition at a time is either not applicable or only of limited utility for such systems.

Real-space electric-field Green functions are derived for a superlattice structure composed of a regular array of thin metal films immersed in a dielectric. The derivation makes use of the jump condition on the magnetic field due to the areal conductivity of the metal and conforms with Bloch’s theorem on the one-dimensional periodicity of the structure along the growth direction. The initial steps lead to mixed (real-space–reciprocal-space) Green functions. We show how the desired all-space Green functions are obtainable from these by Fourier transformation to real space, making use of the symmetry properties of the system. The emission rate for a dipole of a given orientation follows directly from the imaginary part of the appropriate equal-space Green function. The results are investigated for different electron densities and different periodicity lengths and compared with the results appropriate for a single sheet and various asymptotic limits. Also using the same set of Green functions, we determine pair cooperative effects for dipoles embedded in the structure. Interesting features are pointed out when the dipoles have different orientations and/or are situated in different unit cells of the superlattice.

We consider a system of particles in an array of microscopic traps, coupled to each other via electrostatic interaction, and pushed by an external state-dependent force. We show how to implement a two-qubit quantum gate between two such particles with a high fidelity.

A newly developed saddle-point multichannel K-matrix method is used to study the photoionization of lithium from ${1s}^{2}2s$ and ${1s}^{2}2p$ for photon energies near the $2p2p2p$ ${}^2{P}^o$ and $2s2p2p$ ${}^2{L}^e$ $\mathrm{}(L=0,1,2\mathrm{})\mathrm{}$ resonances. Highly accurate initial- and target-state wave functions are used and up to 17 open channels are included in the calculation. The calculated partial and total photoionization cross sections are compared with the available theoretical and experimental data. The partial cross sections obtained in this work suggests that for Li ${1s}^{2}2s$ and ${1s}^{2}2p$ initial states, the $1s$ electron with spin antiparallel to that of the $2s$ (or $2p)$ electron is the one most likely to be ejected in the photoionization process. The elastic and inelastic electron-ion scattering cross sections are also calculated. The relative magnitude of the calculated collision strength is compared with the Auger branching ratios for these resonances.

The zero-range potential is customarily employed in various mean-field calculations of many-body systems in atomic and nuclear physics within, correspondingly, Gross-Pitaevskii and Skyrme-Hartree-Fock approaches. We argue, however, that a many-body system with zero-range potentials is unstable against clusterization into collapsed three-body subsystems. We show that neither the density dependence of the potential nor an additional repulsive three-body potential can prevent this unexpected correlational collapse if the potentials are of zero range. Therefore, the zero-range potential can only be used in many-body calculations where all three-body correlations are explicitly excluded.