A comprehensive search for broad Feshbach resonances (FRs) in all possible combinations of stable alkali-metal atoms is carried out, using a multichannel quantum-defect theory assisted by the analytic wave functions for a long-range van der Waals potential. A number of broad $s$-, $p$-, and $d$-wave FRs in the lowest-energy scattering channels, which are stable against two-body dipolar spin-flip loss, are predicted and characterized. Our results also show that broad FRs of $p$- or $d$-wave type that are free of two-body loss do not exist between fermionic alkali-metal atoms for a magnetic field up to 1000 G. These findings constitute helpful guidance on efforts towards the experimental study of high-partial-wave coupling-induced many-body physics.

Quantum tracking control aims to identify applied fields to steer the expectation values of particular observables along desired paths in time. The associated temporal fields can be identified by inverting the underlying dynamical equations for the observables. However, fields found in this manner are often plagued by undesirable singularities. In this paper we consider a planar molecular rotor and derive singularity-free tracking expressions for the fields that steer the expectation of the orientation of the rotor along the desired trajectories in time. Simulations are presented that utilize two orthogonal control electric fields to drive the orientation of the rotor along a series of designated tracks.

We propose and illustrate a quantum hydrodynamic (QHD) model for the description of plasmonic oscillations in the ${\mathrm{C}}_{60}$ molecule. Although simpler than competing approaches such as time-dependent density-functional theory (TDDFT), the model contains the key ingredients to characterize plasmonic modes, namely the Hartree, exchange, and correlation potentials, as well as nonlocal, nonlinear, and quantum effects to the lowest order. A variational technique is used to solve analytically the QHD model for the case of breathing (monopolar) plasmonic oscillations, revealing a bulk mode near the plasmon frequency. Numerical simulations of both the QHD equations and a TDDFT model confirm the existence of this mode and highlight a second collective mode at lower energy. Such monopolar modes may be measured experimentally using electron energy-loss spectroscopy.

We have experimentally demonstrated both heating and cooling of electrons in an ultracold neutral plasma (UNP) by embedding Rydberg atoms into the plasma soon after its creation. We have determined the relationship between the initial electron temperature, $T_{e,i}$, and the binding energy of the added Rydberg atoms, $E_b$, at the crossover between heating and cooling behaviors (that is, the binding energy of the atoms, which, when they are added to the plasma, neither accelerate nor slow down the plasma expansion). Specifically, this condition is $|E_b|\approx 2.7\times k_B{T}_{e,i}$ when the diagnostic used is the effect of the Rydberg atoms on the plasma asymptotic expansion velocity. Additionally, we have obtained experimental estimates for the amount of heating or cooling which occurs when the Rydberg binding energy does not satisfy the crossover condition. The experimental results for the crossover condition, and the degree of heating or cooling away from the crossover, are in agreement with predictions obtained from numerical modeling of the interactions between Rydberg atoms and the plasma. We have also developed a simple intuitive picture of how the Rydberg atoms affect the plasma, which supports the concept of a “bottleneck” in the Rydberg state distribution of atoms in equilibrium with a coexisting plasma.

We revisit the dynamics of a Bose-Einstein condensate in a double-well potential, from the regime of Josephson plasma oscillations to the self-trapping regime, by means of the Bogoliubov quasiparticle projection method. For a very small imbalance between the left and right wells only the lowest Bogoliubov mode is significantly occupied. In this regime the system performs plasma oscillations at the corresponding frequency, and the evolution of the condensate is characterized by a periodic transfer of population between the ground and the first excited state. As the initial imbalance is increased, more excited modes—though initially not macroscopically occupied—get coupled during the evolution of the system. Since their population also varies with time, the frequency spectrum of the imbalance turns out to be still peaked around a single frequency, which is continuously shifted towards lower values. The nonlinear mixing between Bogoliubov modes eventually drives the system into the the self-trapping regime, when the population of the ground state can be transferred completely to the excited states at some time during the evolution. For simplicity, here we consider a one-dimensional setup, but the results are expected to hold also in higher dimensions.

Light beams with an azimuthal phase dependency of $e^{i\ell \varphi }$ have helical phase fronts and thus carry orbital angular momentum (OAM), a strictly conserved quantity with propagation. Here we engineer quasi-three-dimensional (3D) structured light fields and demonstrate unusual scenarios in which OAM can vary locally in both sign and magnitude along the beam's axis, in a controlled manner, under free-space propagation. To reveal the underlying mechanisms of this phenomenon, we perform full modal decomposition and reconstruction of the generated beams to describe the evolution of their intrinsic OAM and topological charge with propagation. We show that topological transition and the associated variation in local OAM rely on the creation, movement, and annihilation of local vortex charges without disturbing the global net charge of the beam, thus conserving the global OAM while varying it locally. Our results may be perceived as an experimental demonstration of the Hilbert Hotel paradox, while advancing our understanding of topological deformations in general.

An optical scheme for simulating adaptive nonlocality distillation is proposed. In the asymptotic limit, arbitrary correlated nonlocal boxes can be distilled to the maximally nonlocal one, i.e., the Popescu-Rohrlich box [S. Popescu and D. Rohrlich, Found Phys. 24, 379 (1994)]. The major obstacle in simulating the adaptive nonlocality distillation scheme, proposed by Brunner and Skrzypczyk [N. Brunner and P. Skrzypczyk, Phys. Rev. Lett. 102, 160403 (2009)], is how to simulate the nonlocal boxes with a quantum system and to get the output of each box without destroying the quantum state simulating it. Here the nonlocal boxes are simulated by appropriately pre- and postselected polarization entangled photon pairs. The output of the first box is measured without destroying the quantum state, simulating it by exploiting a quantum nondemolition measurement, which is realized by a standard quantum teleportation process. This scheme provides a feasible tool for the experimental study of the manipulation of nonlocality in the postquantum regime and the exact physical principle precisely distinguishing physically realizable correlations from nonphysical ones.

A scheme for improving the sensitivity of quantum thermometry is proposed where the sensing quantum system used to recover the temperature of an external bath is dynamically coupled with an external ancilla (a meter) via a Hamiltonian term ${\widehat{H}}_I$. At variance with previous approaches, our scheme relies neither on the presence of initial entanglement between the sensor and the meter, nor on the possibility of performing joint measurements on the two systems. The advantages we report arise from the fact that the presence of ${\widehat{H}}_I$ interferes with the bath-sensor interaction, transforming the sensor into an effective transducer which extracts the intrinsically incoherent information on the bath temperature, and maps it into coherences in the meter where it can finally be recovered by local measurements.

We have studied the non-Markovianity of a dichotomously driven spin-boson model in the strong-coupling regime in both memory kernel and time convolutionless master-equation formulations. A strong correlation between the decay time of the environmental correlation function and the nonzero non-Markovianity is found in the absence of the external noise. Stochastic driving is shown to create strong non-Markovianity when the dynamics of the system without driving is Markovian. Also, exact analytical expressions for the trace distance distinguishability and the non-Markovianity were obtained for the certain range of the parameters that describe the system and its environment.

We propose a model describing $N$ spin-1/2 systems coupled through $N$-order homogeneous interaction terms, in the presence of local time-dependent magnetic fields. This model can be experimentally implemented with current technologies in trapped ions and superconducting circuits. By introducing a chain of unitary transformations, we succeed in exactly converting the quantum dynamics of this system into that of $2^{N-1}$ fictitious spin-1/2 dynamical problems. We bring to light the possibility of controlling the unitary evolution of the $N$ spins generating Greenberger-Horne-Zeilinger states under specific time-dependent scenarios. Moreover, we show that by appropriately engineering the time dependence of the coupling parameters, one may choose a specific subspace in which the $N$-spin system dynamics takes place. This dynamical feature, which we call time-dependent selective interaction, can generate a cooling effect of all spins in the system.

Color vision is based on the ability of different opsin proteins to tune the absorption band of their chromophore, the retinal protonated Schiff base (RPSB). Two main mechanisms proposed for this tunability are geometric and electrostatic. Here we probe the latter effect experimentally and by a quantum chemical calculation of the absorption by an isolated complex containing the retinal chromophore and molecules with a strong dipole moment. Betaine complexation causes an anomalously large blue shift. The shift provides direct evidence that the strong charge-transfer character of the electronic transition is the cause of the opsin shift, and shows that the electric field of the counterion is responsible for the color tuning, which allows absorption of light in the blue region of the visible spectrum by opsin proteins.

The exploration of photonic systems embracing the concept of parity-time ($\mathcal{PT}$) symmetry has become highly active in recent years. Studies on this topic potentially have significant technological implications, enabling unidirectional transmission in optical systems with unusual states of light. Here, we investigate the existence of a flat band in a two-dimensional photonic crystal and the consequences in the context of $\mathcal{PT}$ symmetry. The flat band is ascribed to a pair of two dipolar states and a monopolar state, which is verified by the proposed coupled mode equations. This flat band is protected by the interactions of these three states; therefore it has tremendous potential to investigate the localized stationary eigenstates, and gives rise to intriguing modulations under the perturbation of gain and loss. Especially, gain-loss configurations predominantly act on the coupling behavior of originally orthogonal states, including thresholdless $\mathcal{PT}$ transition, absence, and emergence of $\mathcal{PT}$ transition. The gain-loss configurations, together with the flat band, determine the peculiar band structures and the resultant interesting transmission phenomena. By means of coupled mode equations, we disclose the dynamics upon the perturbation of the gain and loss and the wave vector, and show various transmission modulations including unidirectional behavior.

To manipulate orbital angular momentum (OAM) carried by light beams, there is a great interest in designing various optical elements from the deep-ultraviolet to the microwave. Normally, the OAM variation introduced by optical elements can be attributed to two terms, namely, the dynamic and geometric phases. Up till now, the dynamic contribution induced by optical elements has been clearly recognized. However, the contribution of geometric phase still seems obscure, especially considering the vector vortex beams. In this work, an analytical formula is derived to fully describe the OAM variation introduced by the nonabsorbing optical elements, which perform space-variant polarization-state manipulations. It is found that the geometric contribution can be further divided into two parts: one is directly related to optical elements and the other one explicitly relies solely on the vortices before and after the transformations. Based on this result, the same OAM variation can be achieved with different combinations of the dynamic and/or geometric contributions. With numerical simulations, it is shown that transformation of the optical vortices can be fully and flexibly designed with a family of optical elements. We believe that these results are helpful to understand the effect of optical elements and offer a new perspective to design the optical elements for manipulating the OAM carried by light beams.

We characterize the anisotropic differential ac-Stark shift for the Dy $626\mathrm{nm}$ intercombination transition, induced in a far-detuned $1070\mathrm{nm}$ optical dipole trap, and observe the existence of a “magic polarization” for which the polarizabilities of the ground and excited states are equal. From our measurements we extract both the scalar and tensorial components of the dynamic dipole polarizability for the excited state, ${\alpha }_E^{\text{s}}=188\left(12\right){\alpha }_{\text{0}}$ and ${\alpha }_E^{\text{t}}=34\left(12\right){\alpha }_{\text{0}}$, respectively, where ${\alpha }_{\text{0}}$ is the atomic unit for the electric polarizability. We also provide a theoretical model allowing us to predict the excited state polarizability and find qualitative agreement with our observations. Furthermore, we utilize our findings to optimize the efficiency of Doppler cooling of a trapped gas, by controlling the sign and magnitude of the inhomogeneous broadening of the optical transition. The resulting initial gain of the collisional rate allows us, after forced evaporation cooling, to produce a quasipure Bose-Einstein condensate of ${}^{162}\mathrm{Dy}$ with $3\times {10}^4$ atoms.

The standard state-dependent Heisenberg-Robertson uncertainty-relation lower bound fails to capture the quintessential incompatibility of observables as the bound can be zero for some states. To remedy this problem, we establish a class of tight (i.e., inequalities are saturated) variance-based sum-uncertainty relations derived from the Lie algebraic properties of observables and show that our lower bounds depend only on the irreducible representation assumed carried by the Hilbert space of state of the system. We illustrate our result for the cases of the Weyl-Heisenberg algebra, special unitary algebras up to rank 4, and any semisimple compact algebra. We also prove the usefulness of our results by extending a known variance-based entanglement detection criterion.

The quasiprobability representation of quantum states addresses two main concerns, the identification of nonclassical features and the decomposition of the density operator. While the former aspect is a main focus of current research, the latter decomposition property has been studied less frequently. In this contribution, we introduce a method for the generalized expansion of quantum states in terms of so-called quasistates. In contrast to the quasiprobability decomposition through nonclassical distributions and pure-state operators, our technique results in classical probabilities and nonpositive semidefinite operators, defining the notion of quasistates, that carry the information about the nonclassical characteristics of the system. Therefore, our method presents a complementary approach to prominent quasiprobability representations. We explore the usefulness of our technique with several examples, including applications for quantum state reconstruction and the representation of nonclassical light. In addition, using our framework, we also demonstrate that inseparable quantum correlations can be described in terms of classical joint probabilities and tensor-product quasistates for an unambiguous identification of quantum entanglement.

Joint remote state preparation (JRSP) is a useful way to securely transfer quantum information encoded in quantum states between distant places without physically sending the states themselves. In this paper we study JRSP of the most general $D$-dimensional quantum state called quDit state, with arbitrary integer $D.$ We first show that, by standard procedures, i.e., by exploiting projective measurements on the Hilbert space of the systems of concern, this task can be completed for the dimensions $2,4$, or 8 only. We then propose a nonstandard protocol by means of a positive operator-valued measurement (POVM), which we suitably design so that our protocol works deterministically for any dimension. We also propose a nonstandard protocol for deterministic JRSP of arbitrary hybrid quDit-quNit entanglement with another POVM. Moreover, we construct quantum circuits to realize the two POVMs in the two nonstandard JRSP protocols mentioned above. Our results may be of interest not only from a theoretical point of view but also from an experimental one.

Heavy polar diatomic molecules are currently one of the leading candidates for probing physics beyond the standard model via studies of time-reversal ($T$) and parity ($P$) violations. In this paper, we analyze the effective electric field ($E_{\mathrm{eff}}$) that is required for determining the electron electric dipole moment (eEDM), and the scalar-pseudoscalar (S-PS) interaction coefficient ($W_s$), in group-12 and group-2 systems. We use a relativistic coupled cluster method for our calculations, and find that group-12 monofluorides have large $E_{\mathrm{eff}}$ and $W_s$ (for example, the values of $E_{\mathrm{eff}}$ and $W_s$ of CnF, the heaviest group-12 fluoride, are 662 GV/cm and 3360 kHz, respectively). The reason for this is the contraction of the valence $s$ and $p$ orbitals due to the weak screening effect of the outermost core's $d$ electron. The calculations of $E_{\mathrm{eff}}$ and $W_s$ show that their ratio, $W_s/E_{\mathrm{eff}}$, increases with $Z$. Based on these results, as well as experimental suitability, we propose SrF and CdF as candidate molecules for experiment.

In this work, we present a computational study on the electron scattering by the two lowest-energy structures of formaldehyde dimers $\left[{\left({\mathrm{H}}_2\mathrm{CO}\right)}_2\right]$: the ${\mathrm{C}}_s$ (dimer I) and the ${\mathrm{C}}_{2h}$ (dimer II). More precisely, differential cross sections (DCS), integral cross sections (ICS), and momentum transfer cross sections for elastic scattering by each conformer were computed in the 0.1–30 eV range. A molecular complex optical potential approach combined with the Padé approximant technique was used to solve the scattering equations. Dimer I and dimer II present DCS and ICS that are different in the 0.1–2.0 eV range (due to the differences in their dipole moments) and similar at energies above 4.0 eV (because of the low power of penetration of the incident electrons). Hence, the conformation of the dimer has minor importance for energies ranging from 4.0 up to 30 eV. Two shape resonances were found in the case of dimer I (one centered at 1.1 eV, corresponding to the continuum ${}^{2}A^{″}$, and another around 1.8 eV, assigned as ${}^{2}A^{\prime }$ scattering symmetry). In dimer II, these resonances were found to be centered at 1.1 eV (due to the continuum ${}^{2}B_g$) and at 1.6 eV (regarding the ${}^{2}A_u$ scattering symmetry). Therefore, conformation plays an important role in the determination of the resonances.

Quadrature bases that incorporate spatiotemporal degrees of freedom are derived as eigenstates of momentum-dependent quadrature operators. The resulting bases are shown to be orthogonal for both the particle-number and the spatiotemporal degrees of freedom. Using functional integration, we also demonstrate the completeness of these quadrature bases.