Populations of heterogeneous, noisy oscillators on a two-dimensional lattice display short-range order. Here, we show that if the oscillators are allowed to actively move in space, the system undergoes instead a Berezenskii-Kosterlitz-Thouless transition and exhibits quasi-long-range order. This fundamental result connects two paradigmatic models—the XY and Kuramoto models—and provides insight into the emergence of order in active systems.

A macroscopic energy barrier is a necessary condition for self-correcting quantum memory. In this Letter, we prove tight bounds on the energy barrier applicable to any quantum code obtained from the hypergraph product of two classical codes. If the underlying classical codes are low-density parity-check codes (LDPC), the energy barrier of the quantum code is shown to be the minimum energy barrier of the underlying classical codes (and their transposes) up to an additive $O(1)$ constant.

Fock states of the quantum harmonic oscillator are fundamental to quantum sensing and information processing, serving as key resources for exploiting bosonic degrees of freedom. Here, we prepare high Fock states in a high-overtone bulk acoustic wave resonator by coupling it to a superconducting qubit and applying microwave pulses designed using quantum optimal control. We characterize the experimentally realized states by employing a criterion for genuine quantum non-Gaussianity (QNG) designed to reveal multiphonon contributions. Although energy relaxation and decoherence limit the achievable fidelities, we demonstrate genuine QNG features compatible with a Fock state $|6⟩$, confirming that the prepared states cannot be generated through Gaussian operations on states with up to Fock state $|5⟩$ contributions. We further investigate the robustness of these QNG features to losses and their utility in sensing displacement amplitudes. In particular, we introduce a hierarchy based on the quantum Fisher information and show that, despite decoherence and measurement imperfections, the prepared states achieve a displacement sensitivity surpassing that of an ideal Fock state $|3⟩$. Our results have immediate applications in quantum sensing and simulations with high-overtone bulk acoustic wave resonator devices.

Using $(2712.4\pm 14.3)\times {10}^6\psi (3686)$ events collected with the BESIII detector at the BEPCII collider, the decay ${\eta }_c\to \gamma \gamma$ in $J/\psi \to \gamma {\eta }_c$ is observed. We determine the product branching fraction $\mathcal{B}(J/\psi \to \gamma {\eta }_c)\times \mathcal{B}({\eta }_c\to \gamma \gamma )=(5.23\pm 0.26_{\mathrm{stat}}\pm 0.30_{\mathrm{syst}})\times {10}^{-6}$. This result is consistent with the lattice QCD calculation $(5.34\pm 0.16)\times {10}^{-6}$ from HPQCD in 2023. By using the world-average values of $\mathcal{B}(J/\psi \to \gamma {\eta }_c)$ and the total decay width of ${\eta }_c$, the partial decay width $\mathrm{\Gamma }({\eta }_c\to \gamma \gamma )$ is determined to be $(11.30\pm 0.56_{\mathrm{stat}}\pm 0.66_{\mathrm{syst}}\pm 1.14_{\mathrm{ref}})\mathrm{keV}$, which deviates from the corresponding world-average value by $3.4\sigma$.

Photon blockades are traditionally classified into conventional and unconventional types, depending on distinct physical mechanisms. Regarding the cavity decay rate $\kappa$, the conventional photon blockade takes place under strong nonlinearity condition ($g>\kappa$), whereas the unconventional photon blockade occurs in the regime of weak nonlinearity ($g<\kappa$). We here propose how to derive an optimal condition for photon blockade utilizing a two-photon Jaynes-Cummings model. Under this condition, the equal-time second-order correlation function reaches its minimum, leading to photon antibunching in both conventional and unconventional photon blockade regimes ($g>\kappa$ and $g<\kappa$), even in $g\sim \kappa$. This characteristic is termed universal photon blockade. By comparing it with the conventional and the unconventional photon blockades in the weak-driving limit, the advantages of universal photon blockade are revealed. Our proposal paves an avenue towards the future study of photon blockades and has potential applications in generating antibunched photons.

Placing an atom and a molecule in a cavity opens the door to initialize molecular dynamics by exciting a level of the atom. This approach enlarges the range of choosing the light source to trigger molecular dynamics substantially. The interplay of the atomic, molecular, and photonic populations gives rise to rich dynamics. The cavity photon plays the role of a mediator between the atom and the molecule and it is found that the photonic population is rather low throughout and its evolution follows that of the molecule. Cavities are known to be subject to losses. In spite of the losses it is demonstrated that the presence of the atom gives rise to a long-lived dynamics that should be of relevance for experimental investigations. The presence of more atoms and molecules is expected to further enrich the dynamics.

Open-shell nonrigid molecular systems exhibiting an internal rotation are likely candidates for a coupling between the spin angular momentum of the unpaired electron and the torsional motion. This electron spin-torsion coupling lacked both an experimental validation and a theoretical modeling. Here, the first experimental observation of the electron spin-torsion coupling is reported analyzing the pure rotational spectrum at millimeter wavelengths of the ${\mathrm{CH}}_3\mathrm{CO}$ radical, a ${}^2\mathrm{\Sigma }$ open-shell molecule displaying an internal rotation of its methyl group. To account for this coupling, a specific Hamiltonian incorporating the rotational, torsional, and electronic degrees of freedom is developed and allows us to reproduce the experimental spectrum. The present demonstration of the electron spin-torsion coupling will undoubtedly be key to future investigations of large open-shell molecules exhibiting a complex internal dynamics.

We theoretically study the transverse charge transport in Josephson junctions based on the tilted Dirac materials with valley-dependent gaps. It is shown that a finite tilt-assisted transverse Josephson Hall current is present under broken time-reversal symmetry. This transverse current is driven by the superconducting phase difference across the junction and exhibits a nonsinusoidal current-phase relation, leading to the transverse Josephson diode effect (TJDE), where the critical currents flowing oppositely along the transverse direction are asymmetric. Compared to the conventional longitudinal Josephson diode effect, the predicted TJDE supports a fully polarized diode efficiency with a 100% quality factor and can completely decouple the input signal path from the output, suggesting potential applications for nonreciprocal superconducting devices.

Hysteresis and metastable states are typical features associated with ergodicity breaking in the first-order phase transition. We explore the scaling relations of nonequilibrium thermodynamics in finite-time first-order phase transitions. Using the Curie-Weiss model as an example, for large systems we find the excess work scales as $v^{2/3}$ when the magnetic field is quenched at a finite rate $v$ across the phase transition. We further reveal a crossover in the scaling of the excess work from $v^{2/3}$ to $v$ when downsizing the system. Our study elucidates the interplay between the finite-time dynamics and the finite-size effect, which leads to different scaling behaviors of the excess work with or without ergodicity breaking.

Systems with sparse, yet long-range interactions, form a rich class capable of exhibiting various interesting physics, including good error correction. In this Letter we show how to simulate any sparse Pauli Hamiltonian with a 2D nearest neighbor Hamiltonian, using fewer resources than previous techniques. As an application we demonstrate how to simulate a good quantum code Hamiltonian, effectively approximating a $[[N,\mathrm{\Omega }(\sqrt{N}),\mathrm{\Omega }(\sqrt{N})]]$ code in two dimensions.

Neutron emission probabilities and half-lives of 37 $\beta$-delayed neutron emitters from ${}^{75}\mathrm{Ni}$ to ${}^{92}\mathrm{Br}$ were measured at the RIKEN Nishina Center in Japan, including 11 one-neutron and 13 two-neutron emission probabilities and six half-lives for the first time that supersede theoretical estimates. These nuclei lie in the path of the weak $r$ process occurring in neutrino-driven winds from the accretion disk formed after the merger of two neutron stars synthesizing elements in the $A\sim 80$ abundance peak. The presence of such elements dominates the accompanying kilonova emission over the first few days and have been identified in the AT2017gfo event, associated to the gravitational wave detection GW170817. Abundance calculations based on over 17 000 simulated trajectories describing the evolution of matter properties in the merger outflows show that the new data lead to an increase of 50%–70% in the abundance of Y, Zr, Nb, and Mo. This enhancement is large compared to the scatter of relative abundances observed in old very metal poor stars and thus is significant in the comparison with other possible astrophysical processes contributing to the light-element production. These results underline the importance of including experimental decay data for very neutron-rich $\beta$-delayed neutron emitters into $r$-process models.

Quantum corrections to electron dynamics in a circularly polarized electromagnetic field are found within the Floquet theory of periodically driven quantum systems. It is demonstrated that emission of photons by an electron rotating under the field leads to the quantum recoil force acting on the electron perpendicularly to the velocity of its forward movement, which differs crucially from the known classical recoil force directed oppositely to the velocity. Physically, such an anomalous radiation reaction arises from the one-loop QED correction to the photon emission and has no analog within the classical electrodynamics. Possible manifestations of this macroscopic QED effect are discussed for electrons in strong laser fields.

Non-Abelian fractionalized quasiparticles in half-integer quantum Hall states have been proposed as a platform for the realization of topologically protected fault-tolerant qubits. We observe half-integer quantum Hall states out to remarkably large Landau level filling factors larger than 30 in dual-gated $\sim 3-10\mathrm{nm}$-thick graphite devices. We identify most as single-component states stabilized by fractional correlations in exterior bilayers. Multicomponent (3,3,1) states with strong correlations between opposite-valley states on opposite sides of the graphite interior also appear. The facile integration of graphite with top and bottom surface gates makes thin film graphite an attractive platform to explore the physics of non-Abelian fractionalized quasiparticles.