We investigate the dynamical mode population statistics and associated first- and second-order coherence of an interacting bosonic two-mode model when the pair-exchange coupling is quenched from negative to positive values. It is shown that for moderately rapid second-order transitions, a new pair-coherent phase emerges on the positive coupling side in an excited state, which is not fragmented as the ground-state single-particle density matrix would prescribe it to be.

We have stabilized an external cavity diode laser to a whispering gallery mode resonator formed by a protrusion of a single-crystal magnesium fluoride cylinder. The cylinder’s compact dimensions ($\lesssim 1\hspace{0.5em}{\mathrm{cm}}^3$) reduce the sensitivity to vibrations and simplify the stabilization of its temperature in a compact setup. In a comparison to an ultrastable laser used for precision metrology we determine a minimum Allan deviation of $20\hspace{0.5em}\mathrm{Hz}$ at an optical wavelength of 972 nm, corresponding to a relative Allan deviation of $6\times {10}^{-14}$, at an integration time of $100\hspace{0.5em}\mathrm{ms}$. This level of instability is compatible with the limits imposed by fundamental fluctuations of the material’s refractive index at room temperature.

We investigate the muonic hydrogen $2P_{3/2}^{F=2}$ to $2S_{1/2}^{F=1}$ transition through a precise, nonperturbative numerical solution of the Dirac equation including the finite-size Coulomb force and finite-size vacuum polarization. The results are compared with earlier perturbative calculations of (primarily) [E. Borie, Phys. Rev. A 71, 032508 (2005);  E. Borie and G. A. Rinker, Rev. Mod. Phys. 54, 67 (1982);  E. Borie, Z. Phys. A 275, 347 (1975) and A. P. Martynenko, Phys. Rev. A 71, 022506 (2005);  A. Martynenko, Phys. At. Nucl. 71, 125 (2008), and K. Pachucki, Phys. Rev. A 53, 2092 (1996)] and experimental results recently presented by Pohl et al. [Nature (London) 466, 213 (2010)], in which this very comparison is interpreted as requiring a modification of the proton charge radius from that obtained in electron scattering and electronic hydrogen analyses. We find no significant discrepancy between the perturbative and nonperturbative calculations, and we present our results as confirmation of the perturbative methods.

We study phase transitions in homogeneous spin-$1$ Bose gases in the presence of long-range magnetic dipole–dipole interactions (DDI). We concentrate on three-dimensional (3D) geometries and employ momentum shell renormalization group to study the possible instabilities caused by the DDI. At the zero-temperature limit where quantum fluctuations prevail, we find the phase diagram to be unaffected by the DDI. When the thermal fluctuations dominate, polar and ferromagnetic condensates with DDI become unstable and we discuss this crossover in detail. On the other hand, the spin-singlet condensate remains stable in the presence of DDI.

An anomalous symmetry of magneto-optical images of ferromagnetic domain walls was reported by Schäfer and Hubert [Phys. Status Solidi A 118, 271 (1990)] and interpreted in terms of light amplitudes proportional to the magnetization gradient. We present analytic and numerical calculations supporting such proportionality under additional conditions implied by classical rules of micromagnetics and address some objections presented by Banno [Phys. Rev. A 77, 033818 (2008)] against such proportionality.

We have created a triply quantum-degenerate mixture of bosonic ${}^{41}\mathrm{K}$ and two fermionic species ${}^{40}\mathrm{K}$ and ${}^6\mathrm{Li}$. The boson is shown to be an efficient coolant for the two fermions, spurring hopes for the observation of fermionic superfluids with imbalanced masses. We observe multiple heteronuclear Feshbach resonances, in particular a wide $s$-wave resonance for the combination ${}^{41}\mathrm{K}$-${}^{40}\mathrm{K}$, opening up studies of strongly interacting isotopic Bose-Fermi mixtures. For large imbalance in the local densities of different species, we enter the polaronic regime of dressed impurities immersed in a bosonic or fermionic bath.

We investigate quantum criticality and universal scaling of strongly attractive Fermi gases confined in a one-dimensional harmonic trap. We demonstrate from the power-law scaling of the thermodynamic properties that current experiments on this system are capable of measuring universal features at quantum criticality, such as universal scaling and Tomonaga-Luttinger liquid physics. The results also provide insights on recent measurements of key features of the phase diagram of a spin-imbalanced atomic Fermi gas [Y. Liao et al., Nature (London) 467, 567 (2010)] and point to further study of quantum critical phenomena in ultracold atomic Fermi gases.

We report the formation of a dual-species Bose-Einstein condensate of ${}^{87}\mathrm{Rb}$ and ${}^{133}\mathrm{Cs}$ in the same trapping potential. Our method exploits the efficient sympathetic cooling of ${}^{133}\mathrm{Cs}$ via elastic collisions with ${}^{87}\mathrm{Rb}$, initially in a magnetic quadrupole trap and subsequently in a levitated optical trap. The two condensates each contain up to $2\times {10}^4$ atoms and exhibit a striking phase separation, revealing the mixture to be immiscible due to strong repulsive interspecies interactions. Sacrificing all the ${}^{87}\mathrm{Rb}$ during the cooling, we create single-species ${}^{133}\mathrm{Cs}$ condensates of up to $6\times {10}^4$ atoms.

We perform high-resolution reflection spectroscopy of a quantum dot resonantly coupled to a pillar microcavity. We show the change in reflectivity as the quantum dot is tuned through the cavity resonance and measure the quantum-dot-induced phase shift using an ultrastable interferometer. The macroscopic phase shift we measure could be extended to the study of charged quantum dot pillar microcavity systems, where it could be exploited to realize a high-efficiency spin photon interface for hybrid quantum information schemes.

We present a direct relation, based upon a monogamic principle, between entanglement of formation (EOF) and quantum discord (QD), showing how they are distributed in an arbitrary tripartite pure system. By extending it to a paradigmatic situation of a bipartite system coupled to an environment, we demonstrate that the EOF and the QD obey conservation relation. By means of this relation we show that in the deterministic quantum computer with one pure qubit the protocol has the ability to rearrange the EOF and the QD, which implies that quantum computation can be understood on a different basis as a coherent dynamics where quantum correlations are distributed between the qubits of the computer. Furthermore, for a tripartite mixed state we show that the balance between distributed EOF and QD results in a stronger version of the strong subadditivity of entropy.

We discuss a simple architecture for a quantum toffoli gate implemented using three trapped ions. The gate, which, in principle, can be implemented with a single laser-induced operation, is effective under rather general conditions and is strikingly robust (within any experimentally realistic range of values) against dephasing, heating, and random fluctuations of the Hamiltonian parameters. We provide a full characterization of the unitary and noise-affected gate using three-qubit quantum process tomography.

The cross section for mutual neutralization in collisions between ${\mathrm{H}}^{+}$ and ${\mathrm{F}}^{-}$ ions at low energies ($E⩽10$ eV) is calculated using a molecular close-coupling approach. Two different representations of the quasidiabatic potentials and couplings of HF are used. The effect of autoionization on the cross section is investigated. The coupled Schrödinger equation for the nuclear motion is solved using a numerical integration of the corresponding matrix Riccati equation and the cross section for mutual neutralization is computed from the asymptotic value of the logarithmic derivative of the radial wave function. The magnitude of the cross section for mutual neutralization in this reaction is small compared to other systems. This can be understood by the lack of avoided crossings at large internuclear distances. Resonant structures are found in the cross section and these are assigned with dominant angular momentum quantum number. The cross section for mutual neutralization in collisions of ${\mathrm{D}}^{+}$ and ${\mathrm{F}}^{-}$ ions is also calculated.

We investigate the combined effect of the particle-particle interaction and non-Hermiticity on the quantum states and energy spectra for a non-Hermitian Bose-Hubbard dimer with complex coupling constant. It is analytically and numerically found that a real energy appears uniquely when a balance between the interaction strength and non-Hermiticity is established. The corresponding quantum state is a stationary state which does not decay in time evolution. The result provides a route for enhancing survival probability of an open many-body system and for incoherently controlling quantum transition between the stationary states by modulating the interaction strength to fit the different balance conditions.

We demonstrate state detection based on coherent Raman repumping and a two-color Raman state transfer. The Raman coupling during detection selectively eliminates unwanted dark states in the fluorescence cycle without compromising the immunity of the desired dark state to off-resonant scattering. We demonstrate this technique using ${}^{137}{\mathit{Ba}}^{+}$ where a combination of Raman coupling and optical pumping leaves the metastable state, $D_{3/2}$ $|F^{\prime \prime }=3,m_F^{\prime \prime }=3\rangle$, optically dark and immune to off-resonant scattering. All other states are strongly coupled to the upper $P_{1/2}$ levels. We achieve a single-shot state-detection efficiency of $89.6\left(3\right)\%$ in a 1-ms integration time, limited almost entirely by technical imperfections. Shelving to $|F^{\prime \prime }=3,m_F^{\prime \prime }=3\rangle$ before detection is performed via a two-color Raman transfer with a fidelity of $1.00\left(3\right)$.

The quantum dynamics of the rotational quenching of the ${}^{24}\mathrm{Mg}$H${}^{+}(X\hspace{0.5em}{}^1{\Sigma }^{+})$ molecular cation interacting with ${}^4\mathrm{He}$(${}^{1}S$) as a buffer gas, at relative temperatures ranging from 1 K down to millikelvins, is described by accurate close coupling scattering calculations on an ab initio potential energy surface. The efficiency of the process is quantitatively analyzed by employing the ab initio quenching rates and cross sections and effective decay rate values are obtained from simple unimolecular kinetics over a broad range of trap conditions.

The amplification of high-order harmonics (HOH) in a plasma-based amplifier is a multiscale, temporal phenomenon that couples plasma hydrodynamics, atomic processes, and HOH electromagnetic fields. We use a one-dimensional, time-dependent Maxwell-Bloch code to compare the natural amplification regime and another regime where plasma polarization is constantly forced by the HOH. In this regime, a 10-MW (i.e., 100 times higher than current seeded soft x-ray laser power), 1.5-$\mu$J, 140-fs pulse free from the parasitic temporal structures appearing on the natural amplification regime can be obtained.

We present a detailed study of coherent population trapping (CPT) in the Hanle configuration in sodium atoms confined inside a glass cell and irradiated with a broadband multimode dye laser light resonant with the $D_1$ line. The presence of several modes spaced by tens of MHz is effective in inhibiting hyperfine optical pumping, thus reducing losses and allowing for efficient trapping. A narrow resonance, whose width is of the order of 1 mG, is observed superimposed on the electromagnetically induced transparency (EIT) resonance. Such a structure is more than two orders of magnitude narrower than the broader one, with significantly reduced power broadening. In order to describe this phenomenon, we developed a theoretical model, based on numerical solutions of density matrix equations, which takes into account the peculiarity of CPT induced by broadband multimode laser light. Results are shown to be in very good agreement with the experimental data. In this framework, the small width and the small amount of power broadening exhibited by this narrow spectral structure are related to the time spent by the atoms to re-enter the laser beam volume after collisions that preserve the orientation. This study offers insight into the mechanisms of atoms depolarization caused by collisions with the cell walls and represents a starting point for the development of techniques for the diagnostics of cell-coating parameters and new applications in metrology and magnetometry.

Coherent properties of a two-dimensional spatially periodic structure, polaritonic crystal (PolC) formed by trapped two-level atoms in an optical cavity array interacting with a light field, are analyzed. By considering the wave function overlapping for both photonic and atomic states, a cubic-quintic complex nonlinear Schrödinger equation is derived for the dynamics of coupled atom-light states, wave function of low-branch polaritons, associated with PolC in the continuous limit. A variational approach predicts that a stable ground-state wave function of PolC exists but is accompanied by an oscillating width. For a negative scattering length, the wave function collapses in the presence of a small quintic nonlinearity appearing due to a three-body polariton interaction. By studying the nonequilibrium (dissipative) dynamics of polaritons with adiabatic approximation, we have shown that the collapse of PolC wave function can be prevented even in the presence of small decaying of a number of polariton particles.

We present a detailed discussion of scalar wave propagation and light intensity transport in three-dimensional random dielectric media with optical gain. The intrinsic length and time scales of such amplifying systems are studied and comprehensively discussed as well as the threshold characteristics of single- and two-particle propagators. Our semianalytical theory is based on a self-consistent Cooperon resummation, representing the repeated self-interference, and incorporates as well optical gain and absorption, modeled in a semianalytical way by a finite imaginary part of the dielectric function. Energy conservation in terms of a generalized Ward identity is taken into account.

We search for the existence of the weakly bound He-He-Mg molecules. The He-He-Mg molecule is treated as a three-body system. By using hyperspherical coordinates, the Schrödinger equation for the triatomic system is solved in the adiabatic approximation. We obtain that the binding of the three atoms is possible. The binding energies of such molecules are estimated.