We study time delay in atomic photoionization by circularly polarized light. By considering the Li atom in an excited $2p$ state, we demonstrate a strong time-delay asymmetry between the photoemission of the target electrons that are co- and counter-rotating with the electromagnetic field in the polarization plane. In addition, we observe the time-delay sensitivity to the polar angle of the photoelectron emission in the polarization plane. This modulation depends on the shape and duration of the electromagnetic pulse.

We study sound propagation in Bose-condensed gases in a highly elongated harmonic trap at finite temperatures. This problem is studied within the framework of the Zaremba-Nikuni-Griffin (ZNG) formalism, which consists of a generalized Gross-Pitaevskii equation for the condensate and a kinetic equation for the thermal cloud. We extend the ZNG formalism to deal with a highly anisotropic trap potential and use it to simulate sound propagation using the trap parameters corresponding to an experiment on sound pulse propagation at finite temperature. We focus on the high-density two-fluid hydrodynamic regime, and explore the possibility of observing first- and second-sound pulse propagation. The results of numerical simulation are compared with analytical results derived from linearized ZNG hydrodynamic equations. We show that the second-sound mode makes the dominant contribution to condensate motion at relatively high temperature, while the first-sound mode makes an appreciable contribution.

We present 17 experimentally confirmed Feshbach resonances in optically trapped ${}^{85}$Rb. Seven of the resonances are in the ground-state channel $(f,m_f)=(2,+2)+(2,+2)$ and nine are in the excited-state channel $(2,-2)+(2,-2)$. We find a wide resonance at high field in each of the two channels, offering possibilities for the formation of larger ${}^{85}$Rb condensates and studies of few-body physics. A detailed coupled-channel analysis is presented to characterize the resonances and also provides an understanding of the inelastic losses observed in the excited-state channel. In addition we have confirmed the existence of one narrow resonance in a $(2,+2)+(3,+3)$ spin mixture.

The dynamic response functions of a strongly interacting fermion gas in a homogeneous space are investigated in a virial expansion to second order. The density response function exhibits transition from atomic to molecular response, as the interaction strength increases and the system undergoes BCS to Bose-Einstein condensate crossover. The qualitative features of density and spin response agree with measurements from the Bragg spectroscopy experiments. The virial response is exact at low density and high temperature, therefore providing a benchmark for many-body response.

We examine a family of intrinsic performance measures in terms of probability distributions that generalize Hellinger distance and Fisher information. They are applied to quantum metrology to assess the uncertainty in the detection of minute changes of physical quantities. We show that different measures lead to contradictory conclusions, including the possibility of arbitrarily small uncertainty for fixed resources. These intrinsic performances are compared with the averaged error in the corresponding estimation problem after single-shot measurements.

Rogue waves are devastating extreme events that occur in many natural systems, and a lot of work has focused on predicting and understanding their origin. In optically injected semiconductor lasers rogue waves are rare ultra-high pulses that sporadically occur in the laser chaotic output intensity. Here we show that these optical rogue waves can be predicted with long anticipation time, that they are generated by a crisis-like process, and that noise can be employed to either enhance or suppress their probability of occurrence. By providing a good understanding of the mechanisms triggering and controlling the rogue waves, our results can contribute to improve the performance of injected lasers and can also enable new experiments to test if these mechanisms are also involved in other natural systems where rogue waves have been observed.

Light storage on the minute scale is an important capability for future scalable quantum information networks spanning intercontinental distances. We employ an ultracold atomic gas confined in a one-dimensional optical lattice for long-term light storage. The differential ac Stark shift of the ground-level microwave transition used for storage is reduced to a sub-Hz level by the application of a magic-valued magnetic field. The $1/e$ lifetime for storage of coherent states of light is prolonged up to 16 s by a microwave dynamic decoupling protocol.

Full characterization of quantum states and processes is a fundamental requirement for verification and benchmarking of quantum devices. It has been realized in systems with few components, but for larger systems it becomes unfeasible because of the exponential growing with the system size of the number of measurements and the amount of computational power required to process them. A new approach for quantum state tomography and quantum process tomography, requiring a limited number of measurements, has been recently introduced by Maciel et al. [Quantum Inf. Comput. 12, 0442 (2012); Int. J. Mod. Phys. C 22, 1361 (2011).], namely variational quantum-process tomography (VQT). Here we adopt the VQT approach for the experimental characterization of two-qubit quantum processes and compare the reconstructed maps with those obtained by standard tomographic methods. The results demonstrate the high performance of this approach and propose VQT as a powerful alternative to the standard quantum process tomography.

We present a simple communication complexity problem where three parties benefit from sharing bound entanglement. This demonstrates that entanglement distillability of the shared state is not necessary in order to surpass classical communication complexity.

Various protocols exist by which a referee can be convinced that two observers share an entangled resource. Such protocols typically specify the types of communication allowed, and the degrees of trust required, between the referee and each observer. Here it is shown that the need for any degree of trust of the observers by the referee can be completely removed via the referee using classical and quantum communication channels appropriately. In particular, trust-free verification of Bell nonlocality, Einstein-Podolsky-Rosen steering, and entanglement, respectively, requires two classical channels, one classical and one quantum channel, and two quantum channels. These channels correspond to suitable inputs of quantum randomness by the referee, which prevent the observers from mimicking entanglement using shared classical randomness. Our results generalize recent work by Buscemi [Phys. Rev. Lett. 108, 200401 (2012)], and offer a perspective on the operational significance of that work. They also offer the possibility of simpler experimental demonstrations of the basic idea of quantum-refereed nonlocality tests.

We consider spin-1/2 fermionic atoms with isotropic Rashba spin-orbit coupling in three directions. The interatomic potential is modeled by a square-well potential. We derive the analytic form of the asymptotic wave functions at short range for two fermions in the subspace of zero net momentum and zero total angular momentum. We show that the spin-orbit coupling has perturbative effects on the short-range asymptotic behavior of the wave functions away from resonances. We argue that our conclusion should hold generally.

We study the dynamics of macroscopically coherent matter waves of an ultracold atomic spin-1 or spinor condensate on a ring lattice of six sites and demonstrate the spatiotemporal internal Josephson effect. Using a discrete solitary mode of uncoupled spin components as an initial condition, the time evolution of this many-body system is found to be characterized by two dominant frequencies leading to quasiperiodic dynamics at various sites. The dynamics of spatially averaged and spin-averaged degrees of freedom, however, is periodic enabling a unique identification of the two frequencies. By increasing the spin-dependent atom-atom interaction strength we observe a resonance state, where the ratio of the two frequencies is a characteristic integer multiple and the spin-and-spatial degrees of freedom oscillate in “unison”. Crucially, this resonant state is found to signal the onset of chaotic dynamics characterized by a broadband spectrum. In a ferromagnetic spinor condensate with attractive spin-dependent interactions, the resonance is accompanied by a transition from oscillatory- to rotational-type dynamics as the time evolution of the relative phase of the matter wave of the individual spin projections changes from bounded to unbounded.

Ultracold bosons in zig-zag optical lattices present a rich physics due to the interplay between frustration induced by lattice geometry, two-body interactions, and a three-body constraint. Unconstrained bosons may develop chiral superfluidity and become a Mott insulator even at vanishingly small interactions. Bosons with a three-body constraint allow for a Haldane-insulator phase in nonpolar gases, as well as pair superfluidity and density-wave phases for attractive interactions. These phases may be created and detected within the current state-of-the-art techniques.

We provide an analytical investigation of the entanglement dynamics for a system composed of an arbitrary number of qubits dissipating into a common environment. Specifically, we consider product initial states with a given number of excitations whose evolution remains confined on low-dimensional subspaces of the operators space. We then find for which pairs of qubits entanglement can be generated and can persist at a steady state. Finally, we determine the stationary distribution of entanglement as well as its scaling versus the total number of qubits in the system.

A systematic study of Y iii atomic properties is carried out using high-precision relativistic all-order method. Recommended values and estimates of their uncertainties are provided for a large number of electric-dipole reduced matrix elements, transition rates, and oscillator strengths for allowed transitions between $ns$, $n{p}_j$, $n{d}_j$, $n{f}_j$, and $n{g}_j$ levels with $n\le 8$. The lifetimes of these levels are also evaluated. Electric-quadrupole and magnetic-dipole matrix elements are calculated to determine lifetimes of the $4d_{5/2}$ and $5s$ metastable levels. The ground-state $E1$, $E2$, and $E3$ static polarizabilities are calculated. This work provides recommended values critically evaluated for their accuracy for a number of Y iii atomic properties for use in theoretical modeling as well as planning and analysis of various experiments. We hope that the present study will stimulate further exploration of Y iii for various applications owing to its interesting structure of different low-lying metastable levels.

The ionization and fragmentation of trapped protonated dGCAT oligonucleotides upon interaction with energetic photons ($h\nu =$ 10–570 eV) and keV C${}^{q+}$ ions was investigated by means of time-of-flight mass spectrometry. The observed fragmentation patterns are dominated by protonated and nonprotonated nucleobase ions and fragments of the deoxyribose moiety. Fragments exceeding the size of nucleosides are almost completely absent. Absorption of VUV photons as well as interaction with keV ions predominantly involves ionization or excitation of molecular valence electrons and accordingly the observed fragmentation patterns exhibit qualitatively similar features. Soft-x-ray-induced ionization of core level electrons accompanied by subsequent emission of an Auger electron shifts the fragment distributions towards smaller masses. This systematic study allows for insights into differences and similarities between ion- and photon-induced excitation and fragmentation mechanisms. In particular, the crucial role of the deoxyribose moiety for radiation-induced DNA damage that was predicted on the basis of gas-phase experiments using isolated deoxyribose molecules is confirmed.

The $l$-mixing effect and state-transfer induced by an external electric field pulse in ultracold Rydberg gases are observed with cesium atoms excited to $\mathit{nS}$ states, and measured with a state selective field ionization technique. High-$l$ states are populated from the initially excited $\mathit{nS}$ states due to non-adiabatic transitions through avoided crossings that are formed between the $\mathit{nS}$ state and the ($n-4$) manifold. The population of the product state is investigated as a function of the electric field pulse parameters. The coherent property of the transfer is demonstrated using a 2-pulse sequence and the results are consistent with the theoretical calculations. This $l$-mixing phenomenon in the electric field may be used to help forming a molecular potential and create Rydberg molecules.

We observed the delayed electron detachment induced by multiphoton absorption of hot, zinc phthalocyanine negative ions (C${}_{32}$H${}_{16}$N${}_8$Zn${}^{-}$) stored in an electrostatic ion storage ring. To examine the critical parameters and conditions that characterize the delayed processes, we performed a theoretical model simulation employing inferred values for molecular properties and experimentally controlled values of excitation laser energy and fluence. The thermal detachment rate was estimated by applying the detailed balance theory, and the internal energy distribution of the ions after multiphoton absorption was calculated as a function of the ion temperature immediately before laser irradiation. Our model simulation well reproduces the experimental results, and demonstrates that the experimental configuration determines the range of the observed detachment rate, namely the detectable energy window of the stored ions. The parameter dependence of the estimated ion temperature on the molecular properties was also obtained.

We analyze the nature of self-localization (SL) of Bose-Einstein condensates in one-dimensional optical lattices in the presence of weak local dissipation. SL has recently been observed in several studies based on the discrete nonlinear Schrödinger equation (DNLS); however, its origin is hitherto an open question. We show that SL is based on a self-trapping crossover in the system. Furthermore, we establish that the origin of the crossover is the Peierls-Nabarro barrier, an energy threshold describing the stability of self-trapped states. Beyond the mean-field description the crossover becomes even sharper, which is also reflected by a sudden change of the coherence of the condensate. While we expect that the crossover can be readily studied in current experiments in deep optical lattices, our results allow for the preparation of robust and long-time coherent quantum states.

We analyze the heating of interacting bosonic atoms in an optical lattice due to intensity fluctuations of the lasers forming the lattice. We focus in particular on fluctuations at low frequencies below the band-gap frequency, such that the dynamics is restricted to the lowest band. We derive stochastic equations of motion, and analyze the effects on different many-body states, characterizing heating processes in both strongly and weakly interacting regimes. In the limit where the noise spectrum is flat at low frequencies, we can derive an effective master equation describing the dynamics. We compute heating rates and changes to characteristic correlation functions both in the perturbation theory limit and using a full time-dependent calculation of the stochastic many-body dynamics in one dimension based on time-dependent density-matrix–renormalization-group methods.