We explore the effect of tunable integrability-breaking dipole-dipole interactions in the equilibrium states of highly magnetic one-dimensional (1D) Bose gases of dysprosium at low temperatures. We experimentally observe that in the strongly correlated Tonks-Girardeau regime, rapidity and momentum distributions are nearly unaffected by the dipolar interactions. By contrast, we also observe that significant changes of these distributions occur when decreasing the strength of the contact interactions. We show that the main experimental observations are captured by modeling the system as an array of 1D gases with only contact interactions, dressed by the contribution of the short-range part of the dipolar interactions. Improvements to theory-experiment correspondence will require different tools tailored to near-integrable models possessing both short- and long-range interactions.

Non-Hermitian zero modes in arrays of coupled optical elements can be tailored to feature a number of interesting properties. In addition to being immune to coupling disorders and remaining pinned at the center of the spectrum, they are not dark modes in general (light intensity does not necessarily vanish in one sublattice), their energy eigenvalues are not restricted to the center of the complex plane, and they can be brought to laser oscillation by carefully patterning the spatial pump profile. In this work, we report on the direct observation of a lasing zero mode in a non-Hermitian three-coupled nanocavity array. We show efficient excitation for nearly equal pump power in the two extreme cavities. Furthermore, its efficiency can be dynamically controlled by pumping the center cavity. The realization of zero-mode lasing in large arrays of coupled nanolasers has potential applications in laser-mode engineering and it opens up promising avenues in optical computing.

We study the equilibrium momentum distribution of strongly interacting one-dimensional mixtures of particles at zero temperature in a box potential. We find that the magnitude of the $1/k^4$ tail of the momentum distribution is not only due to short-distance correlations, but also to the presence of the rigid walls, breaking the Tan relation relating this quantity to the adiabatic derivative of the energy with respect to the inverse of the interaction strength. The additional contribution is a finite-size effect that includes a $k$-independent and an oscillating part. This latter, surprisingly, encodes information on long-range spin correlations.

By explicit counterexample, we show that the “reflected entropy” defined by Dutta and Faulkner is not monotonically decreasing under partial trace, and so is not a measure of physical correlations. In fact, our counterexamples show that none of the Rényi reflected entropies $S_R^{\left(\alpha \right)}$ for $0<\alpha <2$ is a correlation measure; the usual reflected entropy is realized as the $\alpha =1$ member of this family. The counterexamples are given by quantum states that correspond to classical probability distributions, so reflected entropy fails to measure correlations even at the classical level.

Our study investigates the presence of high-dimensional entanglement in a recent demonstration of a noise-resistant quantum key distribution (QKD) protocol presented in [Phys. Rev. X 13, 021001 (2023)]. We determined that it is possible to certify the dimensionality of the distributed entangled states to be at least three. To demonstrate this, we developed an energy-time entanglement discretization technique, as well as an improved witness for entanglement dimensionality. Our results provide insight into the complex relationship between high-dimensional entanglement and the noise resistance of QKD protocols operating in high dimensions.

We study the scattering inside a waveguide of a single photon with a single three-level $\mathrm{\Lambda }$ atom, both of which are in a superposition state. The photon is in a superposition state of two frequencies, whereas the atoms are in a superposition state of two nondegenerate ground states. We find that the scattering depends on both the relative phase between the photon frequencies and the relative phase between the atomic ground states. Our results show that a three-level $\mathrm{\Lambda }$ atom coupled to a waveguide can be used as a photon phase filter that could detect the relative phase between the two frequencies of the photon superposition state.

We investigate a scalable trapped-ion array architecture for quantum control of many particles, extending techniques to access multiple dimensions. Our experimental study focuses on automated loading and shuttling of single ${\mathrm{Mg}}^{+}$ ions within our platform that contains up to 13 trapping sites in a three-dimensional arrangement. When shuttling ions from a loading hub to multiple sites, we achieve a success rate of over 0.99 999 and demonstrate coherence preservation and coherent manipulation of superposition states of a hyperfine qubit during the process. Our findings suggest promising applications of these techniques in future large-scale quantum architectures.

We study a multifunctional device for cold atoms consisting of a three-terminal ring circuit pierced by a synthetic magnetic flux, where the ring can be continuous or discretized. The flux controls the atomic current through the ring via the Aharonov-Bohm effect. Our device shows a flux-induced transition of reflections from an Andreev-like negative density to positive density. Further, the flux can direct the atomic current into specific output ports, realizing a flexible nonreciprocal switch to connect multiple atomic systems or sense rotations. By changing the flux linearly in time, we convert constant matter wave currents into an ac modulated current. This effect can be used to realize an atomic frequency generator and study fundamental problems related to the Aharonov-Bohm effect. We experimentally demonstrate Bose-Einstein condensation into the light-shaped optical potential of the three-terminal ring. Our work opens up the possibility of atomtronic devices for practical applications in quantum technologies.

We propose an optical clock based on ultranarrow transitions in neutral titanium, which exhibit small blackbody radiation and quadratic Zeeman shifts and have wavelengths in the S-, C-, and L-telecommunications fiber bands, allowing for integration with robust laser technology. We calculate relevant properties using a high-precision relativistic hybrid method that combines configuration interaction and coupled-cluster approaches. To identify magic wavelengths, we have completed the largest-to-date direct dynamical polarizability calculations. Finally, we identify challenges that arise from magnetic dipole-dipole interactions and describe an approach to overcome them. A telecommunications-band atomic frequency standard will aid the deployment of optical clock networks and clock comparisons over long distances.

Adiabatic Rapid Passage (ARP) allows the inversion of atomic states much faster than absorption–spontaneous-emission cycles with a concomitant large increase in momentum exchange rate and, hence, the applied optical forces. We have implemented ARP with appropriate modulators and polarizers on metastable He atoms on the $2{}^{3}S\to 2{}^{3}P$ transition at $\lambda \approx$ 1083.3 nm. We have measured the velocity dependence of this force and have been surprised by the appearance of large peaks in the magnitude of this force at regularly spaced velocity intervals. Such unexpected behavior suggests that unexpected coherence effects come into play in optical forces, including those used for laser cooling.

In one spatial dimension, quantum exchange statistics and interactions are inextricably intertwined. As a manifestation, the expansion dynamics of a Tonks-Girardeau gas is characterized by dynamical fermionization (DF), whereby the momentum distribution approaches that of a spin-polarized Fermi gas. Using a phase-space analysis and the unitary evolution of the one-body reduced density matrix, we show that DF can be tailored and reversed, using a generalization of delta-kick cooling (DKC) to interacting systems, establishing a simple protocol to rescale the initial momentum distribution. The protocol applies to both expansions and compressions and can be used for the microscopy of quantum correlations.

We study the dissipative dynamics of a fermionic superfluid in the presence of two-body losses. We use a variational approach for the Lindblad dynamics and obtain dynamical equations for Anderson's pseudospins where dissipation enters as a complex pairing interaction as well as effective, density-dependent, single-particle losses which break the conservation of the pseudospin norm. We show that this latter has key consequences on the dynamical behavior of the system. In the case of a sudden switching of two-body losses, we show that the superfluid order parameter decays much more quickly than the particle density at short times and eventually slows down, setting into a power-law decay at longer timescales driven by the depletion of the system. We then consider a quench of pairing interaction, leading to coherent oscillations in the unitary case, followed by the switching of the dissipation. We show that losses affect the dynamical BCS synchronization by introducing not only damping but also a renormalization of the frequency of coherent oscillations, which depends nonlinearly on the rate of the two-body losses.

The deterministic generation of multiexcitation subradiant states proves to be challenging. Here, we present a viable path towards their transient generation in finite-sized ordered arrays of dipole-dipole coupled quantum emitters, based on incoherent driving of the atomic ensemble. In particular, we show that a maximal coupling to long-lived subradiant states is achieved if only half of the atoms are initially excited. We characterize the nature of the resulting states by calculating the dynamic fluorescence spectrum of the emitted light. Finally, we elucidate the role of coherent interactions during the decay process of sufficiently dense atomic arrays, which result in a coherently driven radiation burst that leads to a subsequent reduction of the chances to prepare multiexcitation subradiant states.

In a solid-state spin system, we experimentally demonstrate a protocol for quantum-state population transfer with an improved efficiency compared to traditional stimulated Raman adiabatic passage (STIRAP). Using the ground-state triplet of the nitrogen-vacancy center in diamond, we show that the required evolution time for high-fidelity state transfer can be reduced by almost one order of magnitude. Furthermore, we establish an improved robustness against frequency detuning caused by magnetic noise as compared to STIRAP. These results provide a powerful tool for coherent spin manipulation in the context of quantum sensing and quantum computation.

We theoretically investigate the superfluid–normal-state Berezinskii-Kosterlitz-Thouless transition in a binary mixture of bosonic atoms with Rabi coupling under balanced densities. We find the nonmonotonic behavior of the transition temperature with respect to the intercomponent coupling and amplification of the transition temperature for finite values of Rabi coupling, but for small intracomponent couplings. We develop the Nelson-Kosterlitz renormalization-group equations in the two-component Bose mixture and obtain the Nelson-Kosterlitz criterion modified by a fractional parameter, which is responsible for half-integer vortices, and by Rabi coupling. Adopting the renormalization-group approach, we clarify the dependence of the Berezinskii-Kosterlitz-Thouless transition temperature on the Rabi coupling and the intercomponent coupling. Analysis of the first and second sound velocities also reveals the suppression of quasicrossing of the two sound modes with a finite Rabi coupling in the low-temperature regime. Our results for a two-dimensional binary Bose superfluid contribute to the understanding of a broad range of multicomponent quantum systems such as two-dimensional multiband superconductors.

We study the question of when investing additional quantum resources in preparing a ground state will improve the aggregate runtime associated with estimating its energy. We analyze Lin and Tong's near-optimal state preparation algorithm and show that it can reduce a proxy for the runtime, the $T$-gate count, of ground-state-energy estimation near quadratically. Resource estimates are provided that specify the conditions under which the added cost of state preparation is worthwhile.

We demonstrate a general three-dimensional semiclassical model as a powerful technique for the study of correlated multielectron escape in atoms driven by infrared laser pulses at intensities where electron-electron correlation prevails. We do so in the context of triple ionization of strongly driven Ne. Our model fully accounts for the singularity in the Coulomb potentials of a recolliding electron with the core and a bound electron with the core as well as for the interaction of a recolliding with a bound electron. To avoid artificial autoionization, our model employs effective potentials to treat the interaction between bound electrons. We show the accuracy of our model by obtaining triple ionization distributions of the sum of the final electron momenta which we find to be in very good agreement with experiments. Also, we explain the main features of these momenta distributions in terms of the prevalent pathways of correlated three-electron escape in Ne. We also show that the different ionization pathways prevailing in three-electron escape in strongly driven Ne versus Ar give rise to different momenta distributions in these two atoms. Our general model may be used to identify novel ultrafast phenomena and to motivate further experiments in strong field science.

We study the application of a square perturbing lattice to the naturally forming hexagonal arrays of dipolar droplets in a dipolar Bose-Einstein condensate. We find that the application of the lattice causes spontaneous pattern formation and leads to frustration in some regimes. For certain parameters, the ground state has neither the symmetry of the intrinsic hexagonal supersolid nor the symmetry of the square lattice. These results may give another axis on which to explore dipolar Bose-Einstein condensates and to probe the nature of supersolidity.

Topological photonic edge states are conventionally formed at the interface between two domains of topologically trivial and nontrivial photonic crystals. Recent works exploiting photonic quantum Hall and quantum-valley-Hall effects have shown that large-area topological waveguide states could be created in a three-layer topological heterostructure that consists of a finite-width domain featuring a Dirac cone sandwiched between two domains of photonic crystals with opposite topological properties. In this Letter, we show that an alternative kind of large-area topological waveguide state could be created employing the photonic analogs of the quantum-spin-Hall effect. Taking the well-used Wu-Hu model in topological photonics as an example, we show that sandwiching a finite-width domain of photonic crystals featuring a double Dirac cone between two domains of expanded and shrunken unit cells could lead to the emergence of large-area topological helical waveguide states distributed uniformly in the middle domain. Importantly, we unveil a power-law scaling related to the size of the band gap within which the large-area helical states reside as a function of the width of the middle domain, which implies that these large-area modes in principle could exist in the middle domain with arbitrary width. Moreover, pseudospin-momentum-locking unidirectional propagations and the robustness of these large-area waveguide modes against sharp bends are explicitly demonstrated. Our work broadens the photonic systems and platforms that could be utilized for large-area-mode–enabled topological waveguiding.