The electron affinity ${}^{e}A$(Se) of selenium is measured by photodetachment microscopy on a cesium-sputtering-produced Se${}^{-}$ ion beam using a single-mode CW dye laser. The measured value of the electron affinity is $16297.276\left(9\right){\mathrm{cm}}^{-1}$, or 2.020 604 6(11) eV, which improves the accuracy of this atomic quantity by a factor of 60.

We investigate the two-photon transport properties inside one-dimensional waveguide side coupled to a cavity. The cavity is doped with a four-level atom. By employing dressed state basis, we show that the atom-cavity molecule produces a nonlinear interaction. The bunching and antibunching of the transmitted and reflected photons can be observed due to the nonlinearity. By tuning the Rabi frequency of the classical field, the transmission and reflection of the correlated photons can be controlled.

Bellman's optimality principle has been of enormous importance in the development of whole branches of applied mathematics, computer science, optimal control theory, economics, decision making, and classical physics. Examples are numerous: dynamic programming, Markov chains, stochastic dynamics, calculus of variations, and the brachistochrone problem. Here we show that Bellman's optimality principle is violated in a teleportation problem on a quantum network. This implies that finding the optimal fidelity route for teleporting a quantum state between two distant nodes on a quantum network with bipartite entanglement will be a tough problem and will require further investigation.

We provide the optimal strategy for the unambiguous quantum reading of optical memories, namely when perfect retrieving of information is achieved probabilistically, for the case where noise and loss are negligible. We describe the experimental quantum optical implementations, and provide experimental results for the single photon case.

We carry out a systematic study of Pb iii properties using a hybrid method that combines configuration interaction and linearized coupled-cluster approaches. The calculations start from a [Xe]$4f^{14}5d^{10}$ Dirac-Fock potential. Excitation energies and lifetimes of the $6p^2$, $6sns$, $6snp$, and $6snd$ ($n\le 9$) states are evaluated. Reduced matrix elements, oscillator strengths, and transition rates are determined for allowed electric-dipole transitions including these states. Extensive comparison with other theoretical and experimental values is carried out. Electric-dipole polarizabilities of the $6s^2{}^1{S}_0$, $6s6p{}^3{P}_0$, and $6s6p{}^3{P}_1$ states in Pb iii and ground state polarizability of Pb${}^{4+}$ are reported.

We report measurements and theoretical simulations of high-order harmonic generation (HHG) in aligned N${}_2$ molecules using a 1200-nm intense laser field when the generating pulse is perpendicular to the aligning one. With increasing laser intensity, the minimum in the HHG spectra first shifts its position and then disappears. Theoretical simulations including the macroscopic propagation effects in the medium reproduce these observations and the disappearance of the minimum is attributed to the additional contribution of HHG from inner orbitals. We also predict that the well-known shape resonance in the photoionization spectra of N${}_2$ should exist in the HHG spectra. It is most clearly seen when the generating laser is parallel to the aligning one and disappears gradually as the angle between the two lasers increases. No clear evidence of this shape resonance has been reported so far when using lasers with different wavelengths. Further experimentation is needed to draw conclusions.

We study ultracold bosons in three dimensions with an anisotropic Rashba-Dresselhaus spin-orbit coupling. We first carry out the exact summation of ladder diagrams for the two-boson $t$ matrix at zero energy. Then, with the $t$ matrix as the effective interaction, we find the ground-state phase diagrams of bosons in mean field as a function of the spin-orbit coupling, the anisotropy, and the scattering lengths between particles in the same and in different pseudospin states. The resulting phase diagrams have much richer structures than those obtained using mean-field couplings, exhibiting three different phases: a plane-wave condensate, a striped condensate, and an unstable phase. The differences between the present approach using the $t$ matrix compared to using mean-field couplings is significant for large scattering lengths, large spin-orbit-coupling strength, or small anisotropy.

We use a dispersion relation in conjunction with the operator product expansion (OPE) to derive model independent sum rules for the dynamic structure functions of systems with large scattering lengths. We present an explicit sum rule for the structure functions that control the density and spin response of the many-body ground state. Our methods are general and apply to either fermions or bosons which interact through two-body contact interactions with large scattering lengths. By employing a Borel transform of the OPE, the relevant integrals are weighted toward infrared frequencies, thus allowing for greater overlap low energy data. Similar sum rules can be derived for other response functions. The sum rules can be used to extract the contact parameter introduced by Tan, including universality violating corrections at finite scattering lengths.

We derive a master equation for the total-system density matrix to treat the evolution of quantum dots and photons in a photonic crystal slab with multiple, coupled, lossy defect cavities. In such systems, when the resonant lossy quasimodes of the system overlap in frequency and space, they are generally nonorthogonal. We find that this nonorthogonality can have important consequences for the system evolution. Our formalism allows for the calculation of multiple-photon effects in the presence of quasimode nonorthogonality. It can be applied to the calculation of strong- and weak-coupling dynamics and to first- and second-order photon correlation functions in a wide variety of complicated coupled-cavity systems. As an example, we apply the formalism to an asymmetric two-cavity photonic crystal slab and demonstrate how quasimode nonorthogonality results in oscillations in the decay of the photons out of the system.

We consider variants of the Jaynes-Cummings-Hubbard model of lattice polaritons, taking into account next-nearest-neighbor, diagonal, and long-range photon hopping in one and two dimensions. These models are relevant for potential experimental realizations of polariton Mott insulators based on trapped ions or microwave stripline resonators. We obtain the Mott-superfluid phase boundary and calculate excitation spectra in the Mott phase using numerical and analytical methods. Including the additional hopping terms leads to a larger Mott phase in the case of trapped ions, and to a smaller Mott phase in the case of stripline resonators, compared to the original model with nearest-neighbor hopping only. The critical hopping for the transition changes by up to about 50 percent in one dimension and by up to about 20 percent in two dimensions. In contrast, the excitation spectra remain largely unaffected.

Using numerical simulations, we show that two coupled qubits can amplify a weak signal about a hundredfold. This can be achieved if the two qubits are biased simultaneously by this weak signal and a strong pump signal, both having frequencies close to the interlevel transitions in the system. The weak signal strongly affects the spectrum generated by the strong pumping drive by producing and controlling mixed harmonics with amplitudes of the order of the main harmonic of the strong drive. We show that the amplification is robust with respect to noise, with an intensity of the order of the weak signal. When deviating from the optimal regime (corresponding to strong qubit coupling and a weak signal frequency equal to the interlevel transition frequency), the proposed amplifier becomes less efficient, but it can still considerably enhance a weak signal (by several tens). We therefore propose to use coupled qubits as a combined parametric amplifier and frequency shifter.

We model optomechanical systems as linear optical amplifiers. This provides a unified treatment of diverse optomechanical phenomena. We emphasize, in particular, the relationship between ponderomotive squeezing and optomechanically induced transparency, two foci of current research. We characterize the amplifier response to quantum and applied classical fluctuations, both optical and mechanical. Further, we apply these results to establish quantum limits on external force sensing both on and off cavity resonance. We find that the maximum sensitivity attained on resonance constitutes an absolute upper limit, not surpassed when detuning off cavity resonance. The theory is extended to a two-sided cavity with losses and limited detection efficiency.

Multimode Gaussian quantum light, which includes multimode squeezed and multipartite quadrature entangled light, is a very general and powerful quantum resource with promising applications in quantum information processing and metrology. In this paper, we determine the ultimate sensitivity in the estimation of any parameter when the information about this parameter is encoded in such light when the mean photon number is large, irrespective of the information extraction protocol used in the estimation and of the measured observable. In addition, we show that an appropriate homodyne detection scheme allows us to reach this ultimate sensitivity. We show that, for a given set of available quantum resources, the most economical way to maximize the sensitivity is to put the most squeezed state available in a well-defined light mode. This implies that it is not possible to take advantage of the existence of squeezed fluctuations in other modes, nor of quantum correlations and entanglement between different modes.

We present a fast and efficient method to compute photonic orientation-dependent local density of states (ODLDOS) in photonic crystals (PCs) based on the point group transform of the vector field. We swiftly calculate the ODLDOS by this method and acquire the same results as that computed based on many more k points in half of the first Brillouin zone (FBZ) in face-center-cubic (fcc) photonic crystals. As an example, we also apply this method to investigate the properties of woodpile photonic crystals and find the remarkable differences in the ODLDOS along different polarization directions.

We show that a Bose-Hubbard model extended with pair-correlated hopping has exact eigenstates, quantum lattice compactons, with complete single-site localization. These appear at parameter values where the one-particle tunneling is exactly canceled by nonlocal pair correlations, and correspond in a classical limit to compact solutions of an extended discrete nonlinear Schrödinger model. Classical compactons at other parameter values, as well as multisite compactons, generically get delocalized by quantum effects, but strong localization appears asymptotically for increasing particle number.

The Hartree energy shift is calculated for a unitary Fermi gas. By including the momentum dependence of the scattering amplitude explicitly, the Hartree energy shift remains finite even at unitarity. Extending the theory also for spin-imbalanced systems allows calculation of polaron properties. The results are in good agreement with more involved theories and experiments.