Energy-filtered quantum states are promising candidates for efficiently simulating thermal states. We explore a protocol designed to transition a product state into an eigenstate located in the middle of the spectrum; this is achieved by gradually reducing its energy variance, which allows us to comprehensively understand the crossover phenomenon and the subsequent convergence toward thermal behavior. We introduce and discuss three energy-filtering regimes (short, medium, and long), and we interpret them as stages of thermalization. We show that the properties of the filtered states are locally indistinguishable from those of time-averaged density matrices, routinely employed in the theory of thermalization. On the other hand, nonlocal quantum correlations are generated in the medium regimes and are witnessed by the Rényi entanglement entropies of subsystems, which we compute via replica methods. Specifically, two-point correlation functions break cluster decomposition, and the entanglement entropy of large regions scales as the logarithm of the volume during the medium filter time.

Quantum error correction (QEC) provides a practical path to fault-tolerant quantum computing through scaling to large qubit numbers, assuming that physical errors are sufficiently uncorrelated in time and space. In superconducting qubit arrays, high-energy impact events can produce correlated errors, violating this key assumption. Following such an event, phonons with energy above the superconducting gap propagate throughout the device substrate, which in turn generate a temporary surge in quasiparticle (QP) density throughout the array. When these QPs tunnel across the qubits’ Josephson junctions, they induce correlated errors. Engineering different superconducting gaps across the qubit’s Josephson junctions provides a method to resist this form of QP tunneling. By fabricating all-aluminum transmon qubits with both strong and weak gap engineering on the same substrate, we observe starkly different responses during high-energy impact events. Strongly gap engineered qubits do not show any degradation in $T_1$ during impact events, while weakly gap engineered qubits show events of correlated degradation in $T_1$. We also show that strongly gap engineered qubits are robust to QP poisoning from increasing optical illumination intensity, whereas weakly gap engineered qubits display rapid degradation in coherence. Based on these results, gap engineering mitigates the threat of high-energy impacts to QEC in superconducting qubit arrays.

We examine nucleosynthesis in the ejecta of black-hole–neutron-star mergers based on the results of long-term neutrino-radiation-magnetohydrodynamics simulations for the first time. We find that the combination of dynamical and postmerger ejecta reproduces a solarlike $r$-process pattern. Moreover, the enhancement level of actinides is highly sensitive to the distribution of both the electron fraction and the velocity of the dynamical ejecta. Our result implies that the mean electron fraction of dynamical ejecta should be $\gtrsim 0.05$ in order to reconcile the nucleosynthetic abundances with those in $r$-process-enhanced, actinide-boost stars. Since the tidal ejecta preserve the neutron richness in the inner crust of premerging neutron stars, this result provides an important constraint for nuclear equations of state if black-hole–neutron-star mergers are responsible for actinide-boost stars.

We revisit the prescription commonly used to define holographic correlators on the celestial sphere of Minkowski space as an integral transform of flat space scattering amplitudes. We propose a new prescription according to which celestial holographic correlators are given by the Mellin transform of bulk time-ordered correlators with respect to the radial direction in the hyperbolic slicing of Minkowski space, which are then extrapolated to the celestial sphere along the hyperbolic directions. This prescription is analogous to the extrapolate definition of holographic correlators in AdS/CFT and, like in AdS, is centered on (off-shell) correlation functions as opposed to (on-shell) $S$-matrix elements. We show that celestial correlators defined in this new way are manifestly recast in terms of corresponding Witten diagrams in Euclidean anti–de Sitter space in perturbation theory. We also discuss the possibility of using this definition of celestial correlators in terms of bulk correlation functions to explore the nonperturbative properties of celestial correlators dual to conformal field theories in Minkowski space.

We study the superradiant phase transition of an array of Rydberg atoms in a dissipative microwave cavity. Under the interplay of the cavity field and the long-range Rydberg interaction, the steady state of the system exhibits an interaction-enhanced superradiance, with vanishing critical atom-cavity coupling rates at a discrete set of interaction strengths. We find that, while the phenomenon can be analytically understood in the case of a constant all-to-all interaction, the enhanced superradiance persists under typical experimental parameters with spatially dependent interactions, but at modified critical interaction strengths. The diverging susceptibility at these critical points is captured by emergent quantum Rabi models, each of which comprises a pair of collective atomic states with different numbers of atomic excitations. These collective states become degenerate at the critical interaction strengths, resulting in a superradiant phase for an arbitrarily small atom-cavity coupling.

We observe an inverse turbulent-wave cascade, from small to large length scales, in a driven homogeneous 2D Bose gas. Starting with an equilibrium condensate, we drive the gas isotropically on a length scale much smaller than its size, and observe a nonthermal population of modes with wavelengths larger than the drive one. At long drive times, the gas exhibits a steady nonthermal momentum distribution. At length scales increasing from the drive one to the system size, this distribution features in turn: (i) a power-law spectrum with an exponent close to the analytical result for a particle cascade in weak-wave turbulence, and (ii) a spectrum reminiscent of a nonthermal fixed point associated with universal coarsening in an isolated 2D gas. In further experiments, based on anisotropic driving, we reveal the complete qualitative picture of how the steady-state cascade forms.

The identification of tipping points is essential for the prediction of collapses or other sudden changes in complex systems. Applications include studies of ecology, thermodynamics, climatology, and epidemiology. However, detecting early signs of proximity to a tipping is made challenging by complexity and nonlinearity. Strongly interacting Rydberg atom gases offer model systems that offer both complexity and nonlinearity, including phase transition and critical slowing down. Here, via an external probe we observe prior warning of the proximity of a phase transition of Rydberg thermal gases. This warning signal is manifested as a deviation from linear growth of the variance with increasing probe intensity. We also observed the dynamics of the critical slowing down behavior versus different timescales and atomic densities, thus providing insights into the study of a Rydberg atom system’s critical behavior. Our experiment suggests that the full critical slowing down dynamics of strongly interacting Rydberg atoms can be probed systematically, thus providing a benchmark with which to identify critical phenomena in quantum many-body systems.

The identification of patterns in space, time, and magnitude, which could potentially encode the subsequent earthquake magnitude, represents a significant challenge in earthquake forecasting. A pivotal aspect of this endeavor involves the search for correlations between earthquake magnitudes, a task greatly hindered by the incompleteness of instrumental catalogs. A novel strategy to address this challenge is provided by the groundbreaking observation by Van der Elst (Journal of Geophysical Research: Solid Earth, 2021) that positive magnitude differences, under specific conditions, remain unaffected by catalog incompleteness. In this Letter, we apply these conditions and provide clear and compelling evidence for the existence of correlations between consecutive positive magnitude differences. Our findings strongly support the scenario where the distribution of subsequent earthquake magnitudes depends on the magnitude of the triggering earthquake.

Theoretical calculations show that twisted double bilayer graphene (TDBG) under a transverse electric field develops a valley Chern number 2 at charge neutrality. Using thermodynamic and thermal activation measurements we report the experimental observation of a universal closing of the charge neutrality gap in the Hofstadter spectrum of TDBG at $1/2$ magnetic flux per unit cell, in agreement with theoretical predictions for a valley Chern number 2 gap. Our theoretical analysis of the experimental data shows that the interaction energy, while larger than the flat-band bandwidth in TDBG near 1° does not alter the emergent valley symmetry or the single-particle band topology.

We consider a half-filled Chern band and its transport properties in two phases that it may form: the electronic Fermi liquid and the composite-fermion Fermi liquid. For weak disorder, we show that the Hall resistivity for the former phase is very small, while for the latter it is close to $2h/e^2$, independent of the distribution of the Berry curvature in the band. At rising temperature and high frequency, we expect the Hall resistivity of the electronic phase to rise, and that of the composite-fermion phase to deviate from $2h/e^2$. At high frequency, sign changes are expected as well. Considering high-frequency transport, we show that the composite fermion phase carries a gapped plasmon mode that does not originate from long ranged Coulomb interaction, and we show how this mode, together with the reflection of electromagnetic waves off the Chern band, allows for a measurement of the composite-fermion Drude weight and Berry curvature. Finally, we consider a scenario of a mixed-phase transition between the two phases—for example, as a function of displacement field—and show that such transition involves an enhancement of the longitudinal resistivity, as observed experimentally.

Resonant pumping of the electronic $f\text{−}f$ transitions in the orbital multiplet of dysprosium ions (${\mathrm{Dy}}^{3+}$) in a complex perovskite ${\mathrm{DyFeO}}_3$ is shown to impulsively launch THz lattice dynamics corresponding to the $B_{2g}$ phonon mode, which is dominanted by the motion of ${\mathrm{Dy}}^{3+}$ ions. The findings, supported by symmetry analysis and density-functional theory calculations, not only provide a novel route for highly selective excitation of the rare-earth crystal lattices but also establish important relationships between the symmetry of the electronic and lattice excitations in complex oxides.

Thermodynamic tradeoff relations quantify the fundamental concept of “no free lunch” in the physical world, suggesting that faster and more precise physical processes come at a higher thermodynamic cost. The key elements in these trade-off relations are the thermodynamic uncertainty relation and speed limit, which are closely tied to information inequalities from which other trade-off relations are derived. Concentration inequalities are relations that complement information inequalities in statistical analyses and have been widely used in various fields. However, their role in thermodynamic trade-off relations remains unclear. This Letter develops thermodynamic concentration inequalities that provide bounds for the distribution of observables in quantum and classical Markov processes. We derive a set of trade-off relations that generalize speed limits and thermodynamic uncertainty relations from the developed thermodynamic concentration inequalities. The derived trade-off relations hold under minimal assumptions of the underlying physical processes. This Letter clarifies the role of concentration inequalities in thermodynamics, paving the way for deriving new trade-off relations.

The dynamics of open quantum systems can be simulated by unraveling it into an ensemble of pure state trajectories undergoing nonunitary monitored evolution, which has recently been shown to undergo measurement-induced entanglement phase transition. Here, we show that, for an arbitrary decoherence channel, one can optimize the unraveling scheme to lower the threshold for entanglement phase transition, thereby enabling efficient classical simulation of the open dynamics for a broader range of decoherence rates. Taking noisy random unitary circuits as a paradigmatic example, we analytically derive the optimum unraveling basis that on average minimizes the threshold. Moreover, we present a heuristic algorithm that adaptively optimizes the unraveling basis for given noise channels, also significantly extending the simulatable regime. When applied to noisy Hamiltonian dynamics, the heuristic approach indeed extends the regime of efficient classical simulation based on matrix product states beyond conventional quantum trajectory methods. Finally, we assess the possibility of using a quasi-local unraveling, which involves multiple qubits and time steps, to efficiently simulate open systems with an arbitrarily small but finite decoherence rate.

We show that quantum entanglement can provide an exponential advantage in learning properties of a bosonic continuous-variable (CV) system. The task we consider is estimating a probabilistic mixture of displacement operators acting on $n$ bosonic modes, called a random displacement channel. We prove that if the $n$ modes are not entangled with an ancillary quantum memory, then the channel must be sampled a number of times exponential in $n$ in order to estimate its characteristic function to reasonable precision; this lower bound on sample complexity applies even if the channel inputs and measurements performed on channel outputs are chosen adaptively or have unrestricted energy. On the other hand, we present a simple entanglement-assisted scheme that only requires a number of samples independent of $n$ in the large squeezing and noiseless limit. This establishes an exponential separation in sample complexity. We then analyze the effect of photon loss and show that the entanglement-assisted scheme is still significantly more efficient than any lossless entanglement-free scheme under mild experimental conditions. Our work illuminates the role of entanglement in learning CV systems and points toward experimentally feasible demonstrations of provable entanglement-enabled advantage using CV quantum platforms.

We present a new perturbative full-shape analysis of BOSS galaxy clustering data, including the full combination of the galaxy power spectrum and bispectrum multipoles, baryon acoustic oscillations, and cross-correlations with the gravitational lensing of cosmic microwave background measured from Planck. Assuming the $\mathrm{\Lambda }\mathrm{CDM}$ model, we constrain the matter density fraction ${\mathrm{\Omega }}_{\mathrm{m}}=0.3138\pm 0.0086$, the Hubble constant $H_0=68.23\pm 0.78\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, and the mass fluctuation amplitude ${\sigma }_8=0.688\pm 0.026$ (equivalent to $S_8=0.703\pm 0.029$). Cosmic structure at low redshifts appears suppressed with respect to the Planck $\mathrm{\Lambda }\mathrm{CDM}$ concordance model at $4.5\sigma$. We explore the implications of this dataset for the recent DESI BAO preference for dynamical dark energy (DDE): the BOSS data combine with DESI BAO and PantheonPlus supernovae competitively compared to the CMB, yielding no preference for DDE, but the same $\sim 10\%$ suppression of structure, with dark energy being consistent with a cosmological constant at 68% CL. Our results suggest that either the data contains residual systematics, or more model-building efforts may be required to restore cosmological concordance.

As a key science project of the Square Kilometre Array (SKA), the discovery and timing observations of radio pulsars in the Galactic Center would provide high-precision measurements of the spacetime around the supermassive black hole, Sagittarius A* (Sgr A*), and initiate novel tests of general relativity. The spin of Sgr A* could be measured with a relative error of $\lesssim 1\%$ by timing one pulsar with timing precision that is achievable for the SKA. However, the real measurements depend on the discovery of a pulsar in a very compact orbit, $P_b\lesssim 0.5\mathrm{yr}$. Here for the first time we propose and investigate the possibility of probing the spin of Sgr A* with two or more pulsars that are in orbits with larger orbital periods, $P_b\sim 2–5\mathrm{yr}$, which represents a more realistic situation from population estimates. We develop a novel method for directly determining the spin of Sgr A* from the timing observables of two pulsars, and it can be readily extended for combining more pulsars. With extensive mock data simulations, we show that combining a second pulsar improves the spin measurement by 2–3 orders of magnitude in some situations, which is comparable to timing a pulsar in a very tight orbit.

We present results from a complete next-to-leading order (NLO) calculation of $e^{+}{e}^{-}\to ZH$ in the standard model effective field theory (SMEFT) framework, including all contributions from dimension-six operators. At NLO, there are novel dependencies on CP violating parameters in the gauge sector, on modifications to the Higgs boson self-couplings, on alterations to the top quark Yukawa couplings, and on four-fermion operators involving the electron and the top quark, among others. We show that including only the logarithms resulting from renormalization group scaling can produce misleading results, and further, we explicitly demonstrate the constraining power of combining measurements from different energy scales.