We study theoretically the creation of an optical centrifuge for the controlled rotation of levitated nanorotors within an optical tweezer. The optical centrifuge's motion is simulated by rapidly rotating the linear polarization of the tightly focused optical field used to form an optical trap. We show that nanorotors, formed by anisotropic nanoparticles levitated within a trap, can be accelerated to well-defined rotational rates in excess of 100 MHz over durations of hundreds of microseconds. The initial conditions required for stable acceleration, based on optical trap properties and the anisotropic susceptibility of the nanorotor are established and confirmed by numerical simulations. We also present initial experiments that have developed tools for the rapid angular acceleration of the polarization vector of the linearly polarized beam that is required to create the centrifuge. We show that over acceleration durations in the $100\mu \mathrm{s}$ range, high rotational speeds could be achieved in modest vacuum.

We describe and analyze a quantum thermometer based on a multilayered collisional model. We propose a qubit system whose architecture provides significant sensitivity even for short interaction times between the ancillae that compose the thermometer probe and the system to be probed. The assessment of the flow of information taking place within the layered thermometer and between system and thermometer reveals that the tuning of the mutual backflow of information has a positive influence on the precision of thermometry, and helps unveiling the information-theoretic mechanisms behind the working principles of the proposed architecture.

Optimization of constrained quantum control problems powers quantum technologies. This task becomes very difficult when these control problems are nonconvex and plagued with dense local extrema. For such problems, current optimization methods must be repeated many times to find good solutions, each time requiring many simulations of the system. Here, we present quantum control via polynomial optimization (QCPOP), a method that eliminates this problem by directly finding globally optimal solutions. The resulting increase in speed, which can be a thousandfold or more, makes it possible to solve problems that were previously intractable. This remarkable advance is due to global optimization methods recently developed for polynomial functions. We demonstrate the power of this method by showing that it obtains an optimal solution in a single run for a problem in which local extrema are so dense that gradient methods require thousands of runs to reach a similar fidelity. Since QCPOP is able to find the global optimum for quantum control, we expect that it will not only enhance the utility of quantum control by making it much easier to find the necessary protocols, but also provide a key tool for understanding the precise limits of quantum technologies. Finally, we note that the ability to cast quantum control as polynomial optimization resolves an open question regarding the computability of exact solutions to quantum control problems.

Several recent experiments have challenged the premise that cuprate high-temperature superconductors approach conventional Landau-BCS behavior in the high-doping limit. We argue, based on an analysis of their superconducting spectra, that anomalous properties seen in the most-studied overdoped cuprates require a pairing interaction that is strongly inhomogeneous on nm length scales. This is consistent with recent proposals that the “strange-metal” phase above $T_c$ in the same doping range arises from a spatially random interaction. We show, via mean-field Bogoliubov-de Gennes (BdG) calculations and time-dependent Ginzburg-Landau (TDGL) simulations, that key features of the observed tunneling spectra are reproduced when both inhomogeneity and thermal phase fluctuations are accounted for. In accord with experiments, BdG calculations find that low-$T$ spectra are highly inhomogeneous and exhibit a low-energy spectral shoulder and broad coherence peaks. However, the spectral gap in this approach becomes homogeneous at high $T$, in contrast to experiments. This is resolved when thermal fluctuations are included within TDGL; in this case, global phase coherence is lost at the superconducting $T_c$ via a broadened BKT transition, while robust phase-coherent superconducting islands persist well above $T_c$. The local spectrum remains inhomogeneous at $T_c$, and the gap is found to fill instead of close with increasing temperature.

Artificial gliders are designed to disperse as they settle through a fluid, requiring precise navigation to reach target locations. We show that a compact glider settling in a viscous fluid can navigate by dynamically adjusting its center of mass. Using fully resolved direct numerical simulations and reinforcement learning, we find two optimal navigation strategies that allow the glider to reach its target location accurately. These strategies depend sensitively on how the glider interacts with the surrounding fluid. The nature of this interaction changes as the particle Reynolds number ${\mathrm{Re}}_p$ changes. Our results explain how the optimal strategy depends on ${\mathrm{Re}}_p$. At large ${\mathrm{Re}}_p$, the glider learns to tumble rapidly by moving its center of mass as its orientation changes. This generates a large horizontal inertial lift force, which allows the glider to travel far. At small ${\mathrm{Re}}_p$, by contrast, high viscosity hinders tumbling. In this case, the glider learns to adjust its center of mass so that it settles with a steady, inclined orientation that results in a horizontal viscous force. The horizontal range is much smaller than for large ${\mathrm{Re}}_p$, because this viscous force is much smaller than the inertial lift force at large ${\mathrm{Re}}_p$.

Exceptional points (EPs) are non-Hermitian spectral degeneracies marking a simultaneous coalescence of eigenvalues and eigenvectors. Despite the fact that multiband $n$-fold EPs ($\mathrm{EP}n\mathrm{s}$) generically emerge as special points on manifolds of $\mathrm{EP}m\mathrm{s}$, where $m<n$, $\mathrm{EP}n\mathrm{s}$ as well as their topological properties have hitherto been studied as isolated objects. In this work, we address this issue and carefully map out the emerging properties of multifold exceptional structures in three and four dimensions under the influence of one or multiple generalized similarities, revealing diverse combinations of $\mathrm{EP}m\mathrm{s}$ in direct connection to $\mathrm{EP}n\mathrm{s}$. We find that simply counting the number of constraints defining the $\mathrm{EP}n\mathrm{s}$ is not sufficient in the presence of similarities; the constraints can also be satisfied by the $\mathrm{EP}m$ manifolds obeying certain spectral symmetries in the complex eigenvalue plane, reducing their dimension beyond what is expected from counting the number of constraints. Furthermore, the in- duced spectral symmetries not always allow for any $\mathrm{EP}m$ manifold to emerge in $n$-band systems, making the plethora of exceptional structures deviate further from naive expectations. We illustrate our findings in simple periodic toy models. By relying on similarity relations instead of the less general symmetries, we simultaneously cover several physically relevant scenarios, ranging from optics and topolectrical circuits to open quantum systems. This makes our predictions highly relevant and broadly applicable in modern research, as well as experimentally viable within various branches of physics.

Certifying genuine nonclassical correlations over long distances is essential for device-independent quantum information. In photonic platforms, however, this remains challenging due to photon loss, which opens the detection loophole, rendering violations increasingly difficult for less-efficient detectors. Eberhard showed that using nonmaximally entangled states lowers the detection-efficiency threshold to 66.7%, but existing photonic approaches are restricted to short distances with linear transmittance scaling. Conversely, single-photon event-ready schemes extend the distance with favorable square-root scaling with channel transmittance, yet still demand detection efficiencies above 82.6%. Here, we propose the first all-photonic, heralded entanglement distribution protocol that unifies these two advances: It achieves a postselection-free violation at the Eberhard limit while preserving twin-field-like scaling. We identify the loss independent of the vacuum component amplitude of the prepared state as the source of this enhancement. Our approach addresses both resilience to loss and scalability, providing a practical route toward long-distance, loophole-free Bell tests and device-independent applications with current technology.

We confirm the existence of a new bulk medium quasiparticle with transverse orbital angular momentum (tOAM) and elucidate its physical origin. The tOAM structure is driven by torques induced by the ponderomotive force of the light in the medium, originating from the magnetic Lorentz force, even for weak light fields. There are two contributions to the material tOAM: One part depends on the pulse spatial shape change as it passes through an interface and the other part depends on medium dispersion. The results, from first principles particle-in-cell simulations of a simple plasma, are in excellent agreement with our theory for general dielectric media [S. W. Hancock et al., Phys. Rev. Lett. 127, 193901 (2021)]. For plasma, there is agreement up to near-critical densities and near-relativistic field strengths.

Exploring ferromagnetic moments in magnetoelectric materials is of both fundamental and technological importance. It enables the control of the correlated state using an uncompensated moment. However, its material realization is challenging owing to its exclusive microscopic mechanisms. Here, we report a nearly isotropic ferromagnetic moment in the magnetoelectric antiferromagnet ${\mathrm{Co}}_4{\mathrm{Ta}}_2{\mathrm{O}}_9$, by performing dc and ac magnetic susceptibility, magnetization, and neutron diffraction measurements on identical single crystals. Combined with the group theory analysis, we demonstrate a $P1$ magnetic space group. This implies that physical activities can occur along any crystallographic direction, which explains the unusual magnetoelectric property of ${\mathrm{Co}}_4{\mathrm{Ta}}_2{\mathrm{O}}_9$. The ground state is classified as the M-type altermagnet based on the magnetic point group. Our study provides essential information to resolve the debate on the magnetic ground state and understand the magnetoelectric properties of the related compound with the prospect of observing and examining the $P1$ magnetic space group or ferromagnet in ferroelectrics.

The multientropy and dihedral measures are a class of tractable measures for multipartite entanglement, which are labeled by the Rényi index (or replica number) $n$ as in the Rényi entanglement entropy. The purpose of this article is to demonstrate that these quantities are useful probes of quantum critical points by examining concrete examples. In particular, we compute the multientropy and dihedral measures in the ($1+1$)-dimensional massless free scalar field theory on a lattice and in the transverse-field Ising model. For $n=2$, we find that the numerical results in both lattice theories quantitatively agree with those from conformal field theoretic calculations. For $n=3$ and $n=4$, we provide predictions of these measures for the massless scalar field theory.

Plasma accelerators utilize strong electric fields in plasma waves to accelerate charged particles, making them a compact alternative to radiofrequency technologies. Discharge capillaries are plasma sources used in plasma accelerator research to provide acceleration targets, or as plasma lenses to capture or focus accelerated beams. They have applications for beam-driven and laser-driven plasma accelerators and can sustain high repetition rates for extended periods of time. Despite these advantages, high-fidelity simulations of discharge capillaries remain challenging due to the range of mechanisms involved and the difficulty to diagnose them in experiments. In this work, we utilize hydrodynamic plasma simulations to examine the discharge process of a plasma cell and discuss implications for future accelerator systems. The simulation model is validated with experimental measurements in a 50-mm-long, 1-mm-wide plasma capillary operating a 12–27 kV discharge at 200–1200 Pa hydrogen pressure. For 20 kV at 870 Pa, the discharge is shown to deposit 178 mJ of energy in the plasma. Potential difficulties with the common density measurement method using ${\text{H}}_{\alpha }$ emission spectroscopy are discussed. This simulation model enables investigations of repeatability, heat flow management, and fine tailoring of the plasma profile with discharges.

We have revisited the nonconserved (or model A) critical dynamics of the two-dimensional Ising model through numerical simulations of its lattice and continuum formulations—Glauber dynamics and the time-dependent Ginzburg-Landau (TDGL) equation, respectively—to analyze them with current tools from surface kinetic roughening. Our study examines two critical quenches, one from an ordered and other one from a disordered initial state, for both of which we assess the dynamic scaling ansatz, the critical exponent values, and the fluctuation field statistics that occur. Notably, the dynamic scaling ansatz followed by the system strongly depends on the initial condition: A critical quench from the ordered phase follows Family-Vicsek (FV) scaling, while a critical quench from the disordered phase shows an initial overgrowth regime with intrinsic anomalous roughening, followed by relaxation to equilibrium. This behavior is explained in terms of the dynamical instability of the stochastic Ginzburg-Landau equation at the critical temperature, whereby the linearly unstable term is eventually stabilized by nonlinear interactions. For both quenches, we have determined the occurrence of probability distribution functions for the field fluctuations, which are time independent along the nonequilibrium dynamics when suitably normalized by the time-dependent fluctuation amplitude. Additionally, we have developed a related interface model for a field that scales as the space integral of the TDGL field (integral GL model). Numerical simulations of this model reveal either FV or faceted anomalous roughening, depending on the critical quenched performed, as well as an emergent symmetry in the fluctuation statistics for a critical quench from the ordered phase.

Quantum phase transitions (QPTs) typically emerge in the thermodynamic limit, yet a single-atom QPT can arise when it is coupled to a coherently driven cavity, which provides a simple and unique platform to engineer quantum states with quantum criticality. In this driven Jaynes-Cummings (JC) model, the cavity field becomes squeezed near the critical point. However, vanishing energy gaps at the critical points lead to nonadiabaticity, hindering the practical realization of squeezing. In this work, we introduce a spin-dependent cavity drive, which induces a synthetic gauge field in the Fock-state lattice and enriches the phase diagram of the driven JC model. Remarkably, the energy spectrum can remain discrete for all driving strengths, allowing an adiabatic preparation of squeezed states with robust energy gaps. Moreover, we identify a topological phase transition characterized by projected winding numbers in the presence of broken chiral symmetry. Our results unveil topology and QPTs in a quantized light-matter system and offer a robust strategy for realizing squeezed states.

This study employs Krylov-based information measures to understand task performance in quantum reservoir computing, a subfield of quantum machine learning. In our study, we show that fidelity and spread complexity can only explain the task performance for short time evolutions of the quantum systems. We then discuss two measures, Krylov expressivity and Krylov observability, and compare them to task performance and the information processing capacity. Our results show that Krylov observability exhibits almost identical behavior to information processing capacity, while being three orders of magnitudes faster to compute. In the case when the system is undersampled, Krylov observability best captures the behavior of the task performance.

This report investigates the role of orbital degrees of freedom in ${\mathrm{CrVO}}_4$, focusing on orbital-driven spin-exchange interactions and spin-phonon coupling through both experiments and first-principles calculations. Combining synchrotron radiation x-ray powder diffraction, Raman spectroscopy, and x-ray absorption fine structure measurements, a significant correlation between magnetic transition and structural modification was identified, revealing spin-lattice coupling at the transition ($T_N$). This coupling is linked to conventional magnetoelastic interactions, even active above $T_N$, supported by both experimental and theoretical findings. The calculations revealed crystal field splitting and orbital nondegeneracy resulting from charge transfer in the $3d^3$ system of ${\mathrm{CrVO}}_4$ due to octahedral symmetry breaking. The study discusses the detailed mechanism of orbital-resolved spin-exchange interactions, leading to one-dimensional A-type antiferromagnetic ordering. Notably, no significant orbital-selective spin-phonon coupling was observed at approximately 200 K ($4T_N$) in ${\mathrm{CrVO}}_4$, in contrast to earlier studies [A. P. Roy et al., Phys. Rev. Lett. 132, 026701 (2024)]. These findings advance the understanding of the fundamental physics in ${\mathrm{CrVO}}_4$ and significantly contribute to the field of spin-orbital-lattice physics in transition metal oxides.

The Josephson effect presents a fundamental example of macroscopic quantum coherence as well as a crucial enabler for metrology (e.g., voltage standard), sensing (e.g., superconducting quantum interference device), and quantum information processing (Josephson qubits). Recently, there has been a major renewal of interest in the effect, following its observation in Bose, Fermi, and dipolar atomic condensates, in exciton-polariton condensates, and in momentum space. We present theoretically a nondestructive, in situ, and real time protocol for observing the ac and dc Josephson effects including integer (recently observed in cold atoms) and fractional (hitherto unobserved in cold atoms) Shapiro steps, using a ring condensate coupled to an optical cavity. Our analysis presents a single-shot metrology standard that does not require measurement of atomic number and that challenges the conventional wisdom that quantum computations cannot be observed without being destroyed. Our results have implications for the fields of atomtronics, sensing, metrology, and quantum information processing.