We study the relationship between momentum-space spin textures projected onto the occupied bands and Wilson loop winding, proving a map between band topology and spin topology in certain restricted symmetry settings relevant to fragile topology. Our results suggest that, in specific scenarios, the spin gap may act as a smoking gun bulk indicator for fragile topology.

Quantum physics allows an object to be detected even in the absence of photon absorption, by the use of so-called interaction-free measurements. We provide a formulation of this protocol using a three-level system, where the object to be detected is a pulse coupled resonantly into the second transition. In the original formulation of interaction-free measurements, the absorption is associated with a projection operator onto the third state. We perform an in-depth analytical and numerical analysis of the coherent protocol, where coherent interaction between the object and the detector replaces the projective operators, resulting in higher detection efficiencies. We provide approximate asymptotic analytical results to support this finding. We find that our protocol reaches the Heisenberg limit when evaluating the Fisher information at small strengths of the pulses we aim to detect—in contrast to the projective protocol that can only reach the standard quantum limit. We also demonstrate that the coherent protocol remains remarkably robust under errors such as pulse rotation phases and strengths, the effect of relaxation rates and detunings, as well as different thermalized initial states.

We develop a discrete fermion approach for modeling the strong interaction of an arbitrary system interacting with continuum electronic reservoirs. The approach is based on a pseudofermion decomposition of the continuum bath correlation functions and is only limited by the accuracy of this decomposition. We show that to obtain this decomposition, one can allow for imaginary pseudofermion parameters, and strong damping in individual pseudofermions, without introducing unwanted approximations. For a noninteracting single-resonant level, we benchmark our approach against an analytical solution and an exact hierarchical-equations-of-motion approach. We also show that, for the interacting case, this simple method can capture the strongly correlated low-temperature physics of Kondo resonance, even in the difficult scaling limit, by employing matrix product state techniques.

Quantum illumination is to discern the presence or absence of a target, where the error probability decays exponentially in the number of copies used. When the target reflectivity is small, the exponential decay constant can be computed using monotone metrics. We explicitly derive analytic formula for the decay constant of an arbitrary Gaussian input state in terms of first- and second-order moments assuming a low reflectivity target. Especially, further assuming large background noise, there is no need of symplectic diagonalization, which highly complicates the computation of decay constants. First, we show that the performance of a displaced two-mode squeezed vacuum (TMSV) state with low squeezing can be similar to that of a TMSV state with high squeezing. Second, we show that it is of utmost importance to prepare an efficient idler memory to outperform coherent states while providing a criterion on the idler memory transmittivity. Finally, we identify the region of physically possible correlations between the signal and idler modes that can outperform coherent states.

Because the attractors of biological networks reflect stable behaviors (e.g., cell phenotypes), identifying control interventions that can drive a system towards its attractors (attractor control) is of particular relevance when controlling biological systems. Driving a network's feedback vertex set (FVS) by node-state override into a state consistent with a target attractor is proven to force every system trajectory to the target attractor, but in biological networks the FVS is typically larger than can be realistically manipulated. External control of a subset of a biological network's FVS was proposed as a strategy to drive the network to its attractors utilizing fewer interventions; however, the effectiveness of this strategy was only demonstrated on a small set of Boolean models of biological networks. Here, we extend this analysis to ensembles of biologically inspired Boolean networks. On these models, we use three structural metrics—PRINCE propagation, modified PRINCE propagation, and CheiRank—to rank FVS subsets by their predicted attractor control strength. We validate the accuracy of these rankings using three dynamical measures: To control, away control, and logical domain of influence. We also calculate the propagation metrics on effective graphs, which incorporate each Boolean model's functional information into edge weights. While this additional information increases the predicting power of structural metrics, we find that the increase with respect to the unweighted network is limited. The propagation metrics in conjunction with the FVS can be used to identify realizable driver node sets by emulating the dynamics that are prevalent in biological networks. This approach only uses the network's structure, and the driver sets are shown to be robust to the specific dynamical model.

We describe an approach to optically trapping small, chemically stable molecules at cryogenic temperatures by buffer-gas loading a deep optical dipole trap. The $\sim 10\mathrm{K}$ trap depth will be produced by a tightly focused, 1064-nm cavity capable of reaching intensities of hundreds of $\mathrm{GW}/{\mathrm{cm}}^2$. Molecules will be directly buffer-gas loaded into the trap using a helium buffer gas at $1.5\mathrm{K}$. The very far-off-resonant, quasielectrostatic trapping mechanism is insensitive to a molecule's internal state, energy level structure, and its electric and magnetic dipole moment. Here, we theoretically investigate the trapping and loading dynamics, as well as the heating and loss rates, and conclude that ${10}^4$–${10}^6$ molecules are likely to be trapped. Our trap would open new possibilities in molecular spectroscopy, studies of cold chemical reactions, and precision measurement, amongst other fields of physics.

Recently it has been discovered that in Weyl semimetals the surface state Berry curvature can diverge in certain regions of momentum. This occurs in a continuum description of tilted Weyl cones, which for a slab geometry results in the Berry curvature dipole associated to the surface Fermi arcs growing linearly with slab thickness. Here we investigate analytically incarnations of lattice Weyl semimetals and demonstrate this diverging surface Berry curvature by solving for their surface states and connect these to their continuum descriptions. We show how the shape of the Fermi arc and the Berry curvature hot-line is determined and confirm the $1/k^2$ divergence of the Berry curvature at the end of the Fermi arc as well as the finite-size effects for the Berry curvature and its dipole, using finite-slab calculations and surface Green's function methods. We further establish that apart from affecting the second-order, nonlinear Hall effect, the divergent Berry curvature has a strong impact on other transport phenomena as the Magnus-Hall effect and the nonlinear chiral anomaly.

The oriented emission of photons from an excited population of molecules, causing luminescence anisotropy, is subject to stochastic processes in a fluid. In addition to the well-known lateral Brownian motion, the population is exposed to random rotational processes as well, leading to a depolarization of the luminescence signal. In contrast, the rotation induced by a flow field, the vorticity, is a deterministic process. This rotation can be expressed in terms of a modified emission distribution function of the population. A model is developed to link these deterministic rotations to polarized intensity signals in an experiment. Analytical results of instantaneous and time-integrated intensity signals are provided, incorporating rotational Brownian motion and luminescence lifetime. The number of intensity signals is restricted to an experimentally feasible case, limiting the measurable results to the magnitude of vorticity components. The sensitivity regarding Brownian rotational motion and luminescence lifetime is evaluated. Next to the simplified solutions for 1- and 2-component vorticity fields, a minimization problem is presented to numerically solve the full problem of a 3-component vorticity field influencing the emission behavior. The developed Python toolbox is validated with a synthetic signals of a round turbulent jet.

In recent years, there has been a growing interest in controlling the motion of microparticles inside and outside a focused laser beam. A hydro-thermophoretic trap was recently reported [Nalupurackal et al., Soft Matter 18, 6825 (2022)], which can trap and manipulate microparticles and living cells outside a laser beam. Briefly, a hydro-thermophoretic trap works by the competition between thermoplasmonic flows due to laser heating of a substrate and thermophoresis away from the hotspot of the laser. Here, we extend that work to demonstrate the controlled roll rotation of a microparticle in a hydro-thermophoretic trap using experiments and theory. We experimentally measure the roll angular velocity of the trapped particle. We predict this roll rotation from theoretical computation of the fluid flow. The expression for the angular velocity fits the experimental data. Our method has potential applications in microrheology by employing a different mode of rotation.

We propose a phase transition on the feasibility of efficient parallel assembly. By introducing the parallel efficiency that measures how efficiently the parallel assembly works, the parallelizable phase is defined by its positive value. The parallelizable-unparallelizable transition is then identified by the nonanalytic change in the parallel efficiency from a positive value to zero. We present two analyzable models to demonstrate this phase transition in the limit of infinite system size.

Bose-Einstein condensates are a promising platform for optical quantum memories but suffer from several decoherence mechanisms, leading to short memory lifetimes. While some of these decoherence effects can be mitigated by conventional methods, density-dependent atom-atom collisions ultimately set the upper limit of the quantum memory lifetime to timescales of seconds in trapped Bose-Einstein condensates. We propose a quantum memory technique that utilizes microgravity as a resource to minimize such density-dependent effects. We show that by using optical atom lenses to collimate and refocus the freely expanding atomic ensembles, in a semi-ideal environment, the expected memory lifetime is only limited by the quality of the background vacuum. We anticipate that this method can be experimentally demonstrated in Earth-bound microgravity platforms or space missions, eventually leading to storage times of minutes and unprecedented time-bandwidth products of ${10}^{10}$.

We study a generalization of the well-known Dicke model, using two dissimilar atoms in the regime of ultrastrongly-coupled cavity quantum electrodynamics. Our theory uses gauge-invariant master equations, which yields consistent results in either of the standard multipolar and Coulomb gauges, including system-bath interactions for open cavity systems. We first show how a second atom can be treated as a sensor atom to measure the output spectrum from a single atom in the ultrastrong-coupling regime, and compare results with the quantum regression theorem, explaining when they can be different. We then focus on the case where the second atom is also ultrastrongly coupled to the cavity, but with different parameters from those of the first atom, which introduces complex coupling effects and additional resonances and spectral features. In particular, we show multiple resonances in the cavity spectra that are visible off-resonance. We also observe clear anticrossing features, which are particularly pronounced when the second atom is tuned through its resonance.

Synthetic dimensions provide a powerful approach for simulating condensed matter physics in cold atoms and photonics, whereby a set of discrete degrees of freedom are coupled together and reinterpreted as lattice sites along an artificial spatial dimension. However, atomic experimental realizations have been limited so far by the number of artificial lattice sites that can be feasibly coupled along the synthetic dimension. Here, we experimentally realize for the first time a very long and controllable synthetic dimension of atomic harmonic trap states. To create this, we couple trap states by dynamically modulating the trapping potential of the atomic cloud with patterned light. By controlling the detuning between the frequency of the driving potential and the trapping frequency, we implement a controllable force in the synthetic dimension. This induces Bloch oscillations in which atoms move periodically up and down tens of atomic trap states. We experimentally observe the key characteristics of this behavior in the real-space dynamics of the cloud, and verify our observations with numerical simulations and semiclassical theory. The Bloch oscillations thus act as a smoking-gun signature of the synthetic dimension, and allow us to characterize the effective band structure. Our methods provide an efficient approach for the manipulation and control of highly excited trap states, and set the stage for the future exploration of topological physics in higher dimensions through the use of a tunable artificial gauge field and finite-range interactions.

By combining inelastic neutron scattering and numerical simulations, we study the quasi-one-dimensional Ising-like quantum antiferromagnet ${\mathrm{BaCo}}_2{\mathrm{V}}_2{\mathrm{O}}_8$ in a longitudinal magnetic field applied along the Ising anisotropy, which is also the chain direction. The external field closes the excitation gap due to the magnetic anisotropy, inducing a transition from the Néel ordered state to an incommensurate longitudinal spin density wave phase. If the field is increased further, another transition into a transverse antiferromagnetic phase takes place at 9 T due to the competition between longitudinal and transverse correlations. We numerically and experimentally show that the model of XXZ chains connected by a weak interchain interaction well reproduces this transition. We also calculate the dynamical susceptibility and demonstrate that it agrees quantitatively with inelastic neutron scattering measurements. In contrast to the abrupt change of magnetic ordering, the spectra do not change much at the transition at 9 T, and the spin dynamics can be described as a Tomonaga-Luttinger liquid. We also refine the modeling of ${\mathrm{BaCo}}_2{\mathrm{V}}_2{\mathrm{O}}_8$ by including a four-site periodic term arising from the crystal structure which enables one to account for an anomaly of the magnetic susceptibility appearing at 19.5 T, as well as for the anticrossing observed in the inelastic neutron scattering spectra.

The decay of an unstable quantum state can be inhibited or enhanced by tailored measurements, known as quantum Zeno effect (QZE) or anti Zeno effect (QAZE). QZE(QAZE) has been intensively explored in terms of the cases of various system-environment couplings, where the time evolution can be affected either by the projective measurements, or through the dissipative couplings to the environment. A general relation between QZE(QAZE) and the dissipation, for arbitrary dissipation strength and periodicity, is yet to be developed. In this paper, we show a framework to unify the QZE(QAZE) and the parity-time ($\mathcal{PT}$) symmetry breaking transition, where the pure dissipative Hamiltonian is mapped onto a $\mathcal{PT}$ symmetric non-Hermitian Hamiltonian. This method uses the $\mathcal{PT}$ symmetry transitions to distinguish QZE and QAZE, and can be applied to analyze the crossover behavior between these two effects. Using a heuristic example of a two-level system which is coupled to environment by periodical dissipation, we show the relation diagram between the QZE(QAZE) and the $\mathcal{PT}$ symmetry breaking transition, in which the QZE appears at an exceptional point that separates the $\mathcal{PT}$ symmetric (PTS) phase and the $\mathcal{PT}$ symmetry broken (PTSB) phase, and ends at the resonance point of the maximum $\mathcal{PT}$ symmetry breaking; after that, QAZE exists at the rest of the PTSB phase and remains in the next PTS phase. This interesting finding reveals a hidden relation between the QZE–QAZE and PTS-PTSB phases in a non-Hermitian quantum system.

Hexagonal manganese oxides $R\mathrm{Mn}{\mathrm{O}}_3$ ($R=\mathrm{Y}$, Ho–Lu, Sc, and In) show intriguing topological ferroelectric domain walls with variable conductivity, leading to domain wall engineering. Despite the numerous experimental studies on these polar nanoscale structures, controlling ferroelectric domains has not been sufficiently investigated. Here, we reveal the unprecedented coexistence of polar-nonpolar nanoscale domains that can be formed by substituting titanium ions in ${\mathrm{HoMnO}}_3$. Unusual polar nanoscale domains are embedded in nonpolar domains with different crystallographic symmetry. This polar-nonpolar coexisting structure is naturally assembled by adjusting the lattice length during a solid-state reaction process. Furthermore, this comprehensive study reveals that the reversible microstructural change with a nonpolar-polar transition is strongly correlated with the oxygen storage properties in $\mathrm{Ho}\left(\mathrm{Mn},\mathrm{Ti}\right){\mathrm{O}}_{3+\delta }$. The present results provide important insight into the nanoscale polar-nonpolar domain coexistence in functional rare-earth manganese oxides, $R\mathrm{Mn}{\mathrm{O}}_3$.

The original Grover's algorithm has a success probability to output a correct solution, while deterministic Grover's algorithms improve the success probability to $100\%$. However, the success probability of deterministic Grover's algorithm decreases in noisy environment. Here we improve the deterministic two-parameter (D2p) Grover's algorithm to reach the upper bound for success probability under phase noise. We prove that it is not possible to design any deterministic Grover's algorithm whose success probability is higher than our improved D2p protocol's under phase noise.

We investigate the anomalous flux state of interacting higher-order topological superconductors (HOTSC) protected by rotation symmetries. By introducing a $\pi$ superconducting flux in 2D HOTSC, we demonstrate the existence of a robust zero mode trapped at the flux center. Remarkably, the rotation symmetry and fermion parity display projective representation inside the $\pi$ flux with $N=2$ supersymmetry algebra. A similar gapless flux pattern also exists in 3D HOTSCs, the flux lines of which carry anomalous helical modes that cannot be realized on purely one-dimensional lattice models. Notably, these exotic phenomena can be manifested in a 2D frustrated quantum magnet whose low energy excitation characterizes emergent Majoranas with HOTSC band structure and the $Z_2$ flux exhibiting supersymmetries.