Tomographic locality is a principle commonly used in the program of finding axioms that pick out quantum theory within the landscape of possible theories. The principle asserts the sufficiency of local measurements for achieving a tomographic characterization of any bipartite state. In this work, we explore the meaning of the principle of tomographic locality by developing a simple scheme for generating a wide variety of theories that violate the principle. In this scheme, one starts with a tomographically local theory—which can be classical, quantum, or postquantum—and a physical symmetry, and one restricts the processes in the theory to all and only those that are covariant with respect to the collective action of that symmetry. We refer to the resulting theories as twirled worlds. We show that failures of tomographic locality are ubiquitous in twirled worlds. From the possibility of such failures in classical twirled worlds, we argue that the failure of tomographic locality (i.e., tomographic nonlocality) does not imply ontological holism. Our results also demonstrate the need for researchers seeking to axiomatize quantum theory to take a stand on the question of whether there are superselection rules that have a fundamental status.

While the special properties of exceptional points (EPs) may improve application relevant features such as hypersensing, often their realization requires a precise fine-tuning of parameters. Here we report the robust formation of EP chains in coupled optical microcavities over intercavity distances $D$ on the order of the cavity size. We find that coupling, or more generally, the availability of an outer (coupling) channel, is sufficient to induce EPs in the parameter space spanned by the refractive index $n$ along with $D$. This occurs even at $D$ of several wavelengths, yielding a network of EPs in parameter space with a periodicity of the order of the wavelength in the $D$ direction. Upon the increase of $n$, we observe a sharp transition in the sign of the chirality measured in one of the cavities that further structures the system properties. While the details of the Riemannian surfaces associated with the formation of exceptional points are mode dependent and allow for a variety of single-cavity chiralities, we find the underlying mechanism to be universal, robust, applicable to other and more general coupled systems, and promising for potential applications such as optical measurements of pressure, voltages, or distances.

Metastability is ubiquitous in diverse complex systems. In open quantum systems, metastability offers protection against dissipation and decoherence, yet its application in quantum batteries remains unexplored. We propose a solid-state open quantum battery where metastable states enable stable superextensive charging without complicated protocols and energy storage with extended lifetime. Using a realistic organic maser platform, we show the controllable manner of the work extraction from the quantum battery, which can be exploited for on-demand coherent microwave emission at room temperature. These results not only demonstrate the usefulness of metastability for developing the quantum batteries robust against energy losses, but also provide a paradigm of the practical quantum device powered up by quantum batteries.

A central requirement in asymmetric quantum nonlocality protocols, such as quantum steering, is the precise reconstruction of state assemblages—statistical ensembles of quantum states correlated with remote classical signals. Existing steering works often rely on simplifying assumptions about detection efficiency and photon loss. Here we introduce a generalized loss model for assemblage tomography that uses conical optimization techniques combined with maximum-likelihood estimation. This approach allows us to accurately estimate assemblages without assuming uniform detection efficiency on the untrusted party's side. Using an evidence-based framework grounded in the Akaike information criterion, we demonstrate faithful reconstructions while balancing model complexity. We validate our results through numerical simulations and an experimental setup, showing robust performance in assemblage estimation when applied to experimentally relevant data.

Incoherent stochastic processes added to unitary dynamics are typically deemed detrimental since they are expected to diminish quantum features such as superposition and entanglement. Instead of exhibiting energy-conserving persistent coherent motion, the dynamics of such open systems feature, in most cases, a steady state, which is approached in the long-time limit from all initial conditions. This can, in fact, be advantageous as it offers a mechanism for the creation of robust quantum correlations on demand without the need for fine-tuning. Here, we show this for a system consisting of two coherently coupled bosonic modes, which is a paradigmatic scenario for the realization of quantum resources such as squeezed entangled states. Rather counterintuitively, the mere addition of incoherent hopping, which results in a statistical coupling between the bosonic modes, leads to steady states with robust quantum entanglement and enables the emergence of persistent coherent nonstationary behavior.

Searches for time-reversal symmetry ($T$) violations using spin sensors are susceptible to spurious frequency shifts and noise from magnetic fields, which can mask signals originating from beyond-standard-model new physics. Therefore, a comagnetometer—an auxiliary sensor that allows mundane magnetic-field effects to be differentiated from new physics—is an essential feature of many precision measurements. We characterize an intrinsic comagnetometer that is available in crystals, which can be used to suppress spurious magnetic-field effects through comparing sets of ions related by spatial reflection symmetry. We find that the new-physics measurement channel can be effectively shielded to better than $10\mu \mathrm{G}$, without the need for active or passive magnetic shields. Our measurements demonstrate precise and accurate control over magnetic systematic errors, laying the groundwork for improved searches of $T$ violation using solid-state systems.

Quantum control plays a crucial role in enhancing precision scaling for quantum sensing. However, most existing protocols require perfect control, even though real-world devices inevitably have control imperfections. Here, we consider a fundamental setting of quantum sensing with time domain imperfections, where the duration of control pulses and the interrogation time are all subject to uncertainty. Under this scenario, we investigate the task of frequency estimation in the presence of a non-Markovian environment. We design a control strategy and prove that it outperforms any control-free strategies, recovering the optimal Heisenberg limit up to a small error term that is intrinsic to this model. We further demonstrate the advantage of our control strategy via experiments on a nuclear magnetic resonance platform. Our findings confirm that the advantage of quantum control in quantum sensing persists even in the presence of imperfections.

We experimentally demonstrate cavity-free feedback cooling of the three lowest-lying collective modes of a Bose-Einstein condensate in a prolate harmonic trap. Using shadowgraph imaging as an in situ probe of the atomic density, we measure the time-dependent centers of mass and widths of the condensate in two dimensions and use these measurements to damp oscillations in the two visible dipole modes and the low-frequency quadrupole mode. By inducing oscillations in the condensate, we show that we can efficiently damp the dipole modes to a final mean phonon occupancy per atom of $<1$.

A density matrix (DM) approach has been successfully developed for modeling the dissociative sequential double ionization of molecules driven by ultrashort intense infrared laser pulses. Here, we extend the DM method to theoretically study the dissociative sequential triple ionization of nitrogen molecules. We first calculate potential-energy curves of the ${\mathrm{N}}_2^{3+}$ states and the transition dipole moments between these ${\mathrm{N}}_2^{3+}$ states using the complete active state self-consistent field method. Using the DM method, we calculate the kinetic-energy release (KER) spectra for the ${\mathrm{N}}_2^{3+}$ dissociating through the ${\mathrm{N}}^{2+}+{\mathrm{N}}^{+}$ channel. We find that our simulated KER spectra agree well with the experimental data by Wu et al. [Phys. Chem. Chem. Phys. 13, 18398 (2011)]. This Letter provides a simple model for theoretically investigating the molecular dissociative sequential triple ionization.

We report observation of self-oscillating supersonic flows in a two-dimensional atomic superfluid. By imposing a local particle sink with strong loss, we induce a convergent radial flow with a spatially bounded supersonic region, forming an acoustic analog of a black-hole horizon and an inner horizon around the sink. The observed superflow appears to be modulated by quasiperiodic bursts of superluminal signals. We measure their frequencies and find agreement with numerical simulations of the frequencies of ring soliton oscillations within the black-hole horizon. The solitons seen in the simulations are emitted from the region between the two horizons in a process that we attribute to the Landau instability. The presented experiment demonstrates a new method for creating supersonic flows in atomic superfluids, which may find applications in quantum simulations of curved spacetime, supersonic turbulence, and self-oscillating dynamics in dissipative many-body systems.

We analyze the Markovian dynamics of a quantum system composed of two interacting quantized fields, each coupled to a thermal reservoir with the same average number of thermal excitations ${\overline{n}}_{\text{th}}$, but with different decay rates ${\gamma }_j$ (with $j=1,2$). By employing superoperator techniques and applying two nonunitary transformations, the Lindblad master equation is reformulated into a von Neumann-like form governed by an effective non-Hermitian Hamiltonian. Under these conditions, the structure of the effective Hamiltonian remains equivalent to that of the zero-temperature case, indicating that the essential features of the system dynamics are preserved even in the presence of thermal excitations. As an illustrative example of the method, photon coincidence rates are presented for an initial state composed of two indistinguishable photons.

We report the enhanced optical transmission in the coherent, off-resonant excitation of Rydberg atom gases at room temperature via a two-photon process. Here thermal resonance-enhanced transparency (TRET) is induced when the detuning of the two lasers is adjusted to compensate the atomic thermal-motion-induced energy shifts, i.e., single- and two-photon Doppler shifts. We show that the atomic velocity is mapped into the transmission of the probe fields, which can be altered by independently and selectively exciting different velocity groups through sweeping the detuning. The maximal transmission in TRET is about 8 times higher than that under electromagnetically induced transparency (EIT). Utilizing the TRET effect, we enhance the sensitivity of a Rydberg microwave receiver to be $28.7{\mathrm{nV}\mathrm{cm}}^{-1}{\mathrm{Hz}}^{-1/2}$, ultimately reaching a factor of 2.1 of the EIT case. When atoms of separate velocity groups are excited simultaneously by multiple laser sets of different detuning, the receiver sensitivity increases with the number of laser sets. Our study paves the way to exploit light-matter interaction via the TRET, and contributes to current efforts in developing quantum sensing, primary gas thermometry, and wireless communication with room-temperature atomic gases.

The Chern-Simons (CS) invariant is a fundamental topological invariant describing the topological invariance of three-dimensional (3D) space based on the Chern-Simons field theory. To date, direct measurement of the CS invariant in a physical system remains elusive. Here, the CS invariant is experimentally measured by quenching a 2D optical Raman lattice with 1/2 spin in ultracold atoms. With a recently developed Bloch state tomography, we measure the expectation values of three Pauli matrices in 2D quasimomentum space plus 1D time $\left[\right(2+1\left)\mathrm{D}\right]$, and then respectively extract the Berry curvature and the corresponding Berry connection. By integrating the product of these two quantities, we obtain the CS invariants near $\pm 1$ and 0, which are consistent with theoretical predictions. We also observe transitions among these values, which indicates the change of the topology of the quantum state in $(2+1)\mathrm{D}$ quantum dynamics.

Singular optics studies light's topological defects, pioneered by the discovery that phase vortex lines, strands of destructive interference, naturally occur in scalar wave fields. General electromagnetic waves, however, are described by three-dimensional vectors making scalar phase vortices, which depend on the choice of coordinate basis, less meaningful. Polarization singularities instead capture the vector texture of nonparaxial light with separate descriptions for the electric and magnetic fields. But these polarization textures cannot be fundamental because electromagnetic laws can be expressed not only by separate electric and magnetic fields, but by linear combinations of the two. We propose fundamental, basis-independent topological features generic in electromagnetic fields: one- and two-dimensional structures that relate to time-averaged symmetries held locally by the combined electric- and magnetic-field polarization geometry.

Quantum criticality of open many-body systems has attracted lots of interest for emergent phenomena and universality. Here we present the exact steady state of the quantum van der Pol oscillator using the complex $P$-representation. We show the threshold corresponds to a dissipative phase transition with abrupt changes of steady-state properties and enhanced metrology. The critical behaviors and finite-size effects are investigated through the analytical steady state. We obtain divergent quantum Fisher information (QFI) in the thermodynamic limit both at the critical point and in the time crystal phase, but only the QFI at the critical point approaches the Heisenberg limit. We further prove that the steady-state photon number is the optimized estimated observable with the largest signal-to-noise ratio. We show that the Heisenberg-limited metrology originates from the enhancement of the photon number's susceptibility with a scaling larger than the enhancement of the standard deviation of the photon number. Our work reveals the underlying relation between the time crystal, dissipative phase transition, and enhanced metrology.

Connecting two surface-code patches may require significantly higher noise at the interface. We show, via circuit-level simulations under a depolarizing noise model with idle errors, that surface codes remain fault tolerant despite substantially elevated interface error rates. Specifically, we compare three strategies—direct noisy links, gate teleportation, and a CAT-state gadget—for both rotated and unrotated surface codes, and demonstrate that careful design can mitigate hook errors in each case so that the full code distance is preserved for both $X$ and $Z$. Although these methods differ in space and time overhead and performance, each offers a viable route to modular surface-code architectures. Our results, obtained with stim and pymatching, confirm that high-noise interfaces can be integrated fault-tolerantly without compromising the code's essential properties, indicating that fault-tolerant scaling of error-corrected modular devices is within reach with current technology.

Dipolar supersolids—quantum states that are simultaneously superfluid and solid—have had their superfluid nature rigorously tested, while their solid nature remain uncharted. Arguably, the defining characteristic of a solid is the existence of elastic shear waves. In this work we investigate transverse wave packet propagation in dipolar supersolids with triangular and honeycomb structure. Remarkably, the honeycomb supersolid displays anomalous dispersion, supporting waves traveling faster than the transverse speed of sound. While the distinction between anomalous and normal dispersion appears subtle, it has a profound influence on both the transport and scattering properties. For both supersolid phases, we calculate the shear modulus, a key parameter that quantifies the material's rigidity. Our findings are pertinent to current experimental efforts scrutinizing the fundamental properties of supersolids.

Contextuality is a fundamental property of quantum mechanics. Contrary to entanglement, which can only exist in composite systems, contextuality is also present for single entities. The case of a three-level system is of particular interest because—in agreement with the Bell-Kochen-Specker theorem—it is the simplest in which quantum contextuality is necessarily present. We verify that the polarizations of spin-1 massive particles produced at collider experiments indeed exhibit contextuality. To this purpose we consider $W$ gauge bosons produced in top-quark decays, $J/\psi$ and $K^{*}{\left(892\right)}^0$ mesons created in $B$-meson decays, and $\varphi$ mesons resulting from ${\chi }_c^0$ charmonium decays, making use of the data collected and analyzed by the ATLAS, LHCb, and BESIII collaborations, respectively. The polarizations of all these four particles show contextuality with a significance of more than $5\sigma$.

We present a cooling method for a strongly interacting trapped quantum gas. By applying a magnetic-field modulation with frequencies close to the binding energy of a molecular bound state we selectively remove dimers with high kinetic energy from the sample. We demonstrate cooling of the sample over a wide range of interaction strengths and measure a high cooling efficiency of $\gamma =4$ that exceeds all previous cooling near Feshbach resonances.

Manipulating intracluster ion-molecule reactions via the control of vibrational excitation states of the parent cluster ion holds significant promise. Herein, we studied the effect of vibrational excitation on intracluster ion-molecule reactions within the ethylene dimer ion ${\left({\mathrm{C}}_2{\mathrm{H}}_4\right)}_2{}^{+}$ focusing on the formation of ${\mathrm{C}}_4{\mathrm{H}}_8{}^{+}, {\mathrm{C}}_3{\mathrm{H}}_5{}^{+}$, and ${\mathrm{C}}_4{\mathrm{H}}_7{}^{+}$ ions, utilizing femtosecond laser pulses and ab initio calculations. Via coincident photoelectron and ion detection, we reconstructed the initial vibrational excitation state population (IVP) of the parent ion and found a correlation between the IVP and product formation. Our study shows that the branching ratios for ${\mathrm{C}}_4{\mathrm{H}}_8{}^{+}, {\mathrm{C}}_4{\mathrm{H}}_7^{+}$, and ${\mathrm{C}}_3{\mathrm{H}}_5^{+}$ ions are dominated by low, medium, and high vibrational states, respectively, and there is a clear competition among them. Further analysis confirmed that laser intensity affects the IVP, which determines the yield of each decay channel. Our study establishes a direct link between IVP and product distribution in intracluster ion-molecule reactions and demonstrates the potential to steer reaction outcomes by varying laser field intensity, which opens avenues to the tailored control of reactions in various intracluster systems.