Quantum information cannot be broadcast—an intrinsic limitation imposed by quantum mechanics. However, recent advances in virtual operations offer new insights into the no-broadcasting theorem. Here, we focus on the practical utility and introduce sample efficiency as a fundamental constraint, requiring any practical broadcasting protocol perform no worse than the naive approach of direct preparation and distribution. We prove that no linear process—whether quantum or beyond—can simultaneously uphold sample efficiency, unitary covariance, permutation invariance, and classical consistency. This leads to a no-practical-broadcasting theorem, which places strict limits on the practical distribution of quantum information. By applying Schur-Weyl duality, we establish the uniqueness of the canonical 1-to-$N$ virtual broadcasting map that satisfies the latter three conditions, provide its construction, and determine its sample complexity through semidefinite programming. Finally, we explore the interplay between virtual broadcasting and a quantum spacetime framework, known as the pseudodensity operator, showing that their correspondence holds only in the 1-to-2 case, underscoring the fundamental asymmetry between spatial and temporal statistics in the quantum world.

Muon colliders provide an exciting new direction to expand the energy frontier of particle physics. We point out a new use of these facilities for neutrino and beyond the standard model physics using their main detectors. Muon decays along the accelerator rings create an intense and highly collimated neutrino beam that crosses a thin slice of the kt-scale detector. As a result, it would induce an unprecedented number of neutrino interactions, with $\mathcal{O}({10}^4)$ events per second for a 10 TeV ${\mu }^{+}{\mu }^{-}$ collider. These interactions are highly energetic and possess a distinct timing signature and a large transverse displacement. We discuss promising applications of these events for instrumentation, electroweak, and beyond-the-standard model physics. For instance, a subpercent measurement of the neutrino-electron scattering rate enables new precision measurements of the Weak angle and a novel detection of the neutrino charge radius.

Axions, originally proposed to resolve the $CP$ problem in the strong interaction, remain a leading dark matter candidate. While cavity haloscopes offer the most sensitive technique for detecting axions, searches have largely been limited to masses below $10\mathrm{\mu eV}$. We report a sensitive search for axion dark matter with masses around $21\mathrm{\mu eV}$, utilizing the ${\mathrm{TM}}_{020}$ mode of a cylindrical cavity equipped with an innovative tuning mechanism. Our search achieved a sensitivity of $1.7\times$ the Kim-Shifman-Vainshtein-Zakharov benchmark over a 100-MHz range, representing a significant advance in this mass range. These results demonstrate that higher-order modes provide a viable strategy for extending haloscope searches into previously unexplored higher-mass regions.

We have observed amplification of weak fluorescence from He atoms in the 3a ${}^1{P}^o$ autoionizing state, which decay by spontaneous emission of 40.74 eV photons in one out of 1600 cases. On average, a $4.1\pm 1.6\%$ conversion of 63.67 eV photons was detected in the forward direction at $20\mathrm{\mu }\mathrm{J}$ pump pulse energy and 40 mbar He gas pressure. A comparison with state-of-the-art theoretical simulations shows an unexpected spectral line shift at high gas pressure that is ascribed to transient molecular and electron scattering effects.

Using the strong dispersive coupling to a high-cooperativity cavity, we demonstrate fast and nondestructive number-resolved detection of atoms in optical tweezers. We observe individual atom-atom collisions, quantum state jumps, and atom loss events with a time resolution of $100\mathrm{\mu }\mathrm{s}$ through continuous measurement of cavity transmission. Using adaptive feedback control in combination with the nondestructive measurements, we further prepare a single atom with 92(2)% probability.

Quantum state lifetimes $T_2$, or equivalently homogeneous linewidths ${\mathrm{\Gamma }}_h=1/\pi T_2$, are a key parameter for understanding decoherence processes in quantum systems and assessing their potential for applications in quantum technologies. The most common tool for measuring narrow optical homogeneous linewidths, i.e., long $T_2$, is the measurement of coherent photon echo emissions, which however gives very weak signal when the number of emitters is small. This strongly hampers the development of nanomaterials, such as those based on rare earth ions, for quantum communication and processing. In this work, we propose, and demonstrate in an erbium doped crystal, a measurement of photon echoes based on incoherent fluorescence detection and its variance analysis. It gives access to $T_2$ through a much larger signal than direct photon echo detection, and, importantly, with a laser which is incoherent over the measurement timescale, on the order of a few $T_2$. Our results thus open the way to efficiently assess the properties of a broad range of emitters and materials for applications in quantum nanophotonics.

In the underdense, or blowout regime, of plasma wakefield acceleration, the particle beam is denser than the plasma. In this scenario, the plasma electrons are nearly completely rarefied from the beam channel, leaving only a nominally uniform ion-filled “bubble.” Extensive investigations of this interaction assuming axisymmetry have been undertaken. However, the blowout produced by a transversely asymmetric (flat) driver, which would be present in linear collider “afterburner” schemes, possesses quite different characteristics. Such beams create an asymmetric plasma bubble which leads to unequal focusing in the two transverse dimensions, accompanied by a nonuniform accelerating gradient. The asymmetric blowout cross section is found through simulation to be elliptical, and treating it as such permits a simple extension of the symmetric theory. In particular, focusing fields linear in both transverse directions inside the bubble are found. The form of the wake potential and the associated beam-matching conditions in this elliptical cavity are discussed. We also examine blowout boundary estimation in the long driver limit and applications of the salient asymmetric features of the wakefield.

While topology can impose obstructions to exponentially localized Wannier functions, certain topological insulators are exempt from such Wannier obstructions. The absence of the Wannier obstructions can further accompany topological boundary states that are detachable from the bulk bands. Here, we elucidate a close connection between these detachable topological boundary states and non-Hermitian topology. Identifying Hermitian topological boundary states as non-Hermitian topology, we demonstrate that intrinsic non-Hermitian topology leads to the inevitable spectral flow. By contrast, we show that extrinsic non-Hermitian topology underlies the detachment of topological boundary states and clarify anti-Hermitian topology of the detached boundary states. Based on this connection and $K$-theory, we complete the tenfold classification of Wannier localizability and detachable topological boundary states.

An excitonic insulator is a material that hosts an exotic ground state, where an energy gap opens due to spontaneous condensation of bound electron-hole pairs. ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ is a promising candidate for this type of material, but the coexistence of a structural phase transition with the gap opening has led to a long-standing debate regarding the origin of the insulating gap. Here we employ MeV ultrafast electron diffraction to obtain quantitative insights into the atomic displacements in ${\mathrm{Ta}}_2{\mathrm{NiSe}}_5$ following photoexcitation, which has been overlooked in previous time-resolved spectroscopy studies. In conjunction with first-principles calculations using the measured atomic displacements, we find that the structural change can largely account for the photoinduced reduction in the energy gap without considering excitonic effects. Our Letter illustrates the importance of a quantitative reconstruction of individual atomic pathways during nonequilibrium phase transitions, paving the way for a mechanistic understanding of a diverse array of phase transitions in correlated materials where lattice dynamics can play a pivotal role.

We derive fluctuation-response inequalities for Markov jump processes that link the fluctuations of general observables to the response to perturbations in the transition rates within a unified framework. These inequalities are derived using the Cramér-Rao bound, enabling broader applicability compared to existing fluctuation-response relations formulated for static responses of currentlike observables. The fluctuation-response inequalities are valid for a wider class of observables and are applicable to finite observation times through dynamic responses. Furthermore, we extend these inequalities to open quantum systems governed by the Lindblad quantum master equation and find the quantum fluctuation-response inequality, where dynamical activity plays a central role.

Coupled Kerr parametric oscillators (KPOs) are a promising resource for classical and quantum analog computation, for example to find the ground state of Ising Hamiltonians. Yet, the state space of strongly coupled KPO networks is very involved. As such, their phase diagram sometimes features either too few or too many states, including some that cannot be mapped to Ising spin configurations. This complexity makes it challenging to find and meet the conditions under which an analog optimization algorithm can be successful. Here, we demonstrate how to use three strongly coupled KPOs as a simulator for an Ising Hamiltonian, and estimate its ground state using a Boltzmann sampling measurement. While fully classical, our Letter is directly relevant for quantum systems operating on coherent states.

The quantification of disorder in data remains a fundamental challenge in science, as many phenomena yield short length datasets with order-disorder behavior, significant (un)correlated fluctuations, and indistinguishable characteristics even when arising from distinct natures, such as chaotic or stochastic processes. In this Letter, we propose a novel method to directly quantify disorder in data through recurrence microstate analysis, showing that maximizing this measure is essential for its optimal estimation. Our approach reveals that the disorder condition corresponds to the action of the symmetric group on recurrence space, producing classes of equiprobable recurrence microstates. By leveraging information entropy, we define a robust quantifier that reliably differentiates between chaotic, correlated, and uncorrelated stochastic signals even using just small time series. Additionally, it uncovers the characteristics of corrupting noise in dynamical systems. As an application, we show that disorder minima over time often align with well-known stage transitions of the Cenozoic era, indicating periods of dominant drivers in paleoclimatic data.

We present an experimental study on the collective behavior of macroscopic self-propelled particles that are externally excited by light. This property allows for testing the system response to the excitation intensity in a very versatile manner. We discover that, for low excitation intensities, clustering at the boundaries is always present, even when this is prevented by implementing flower-shaped confining walls. For high excitation intensities, however, clusters are dissolved more or less easily depending on their size. Then, a thorough analysis of the cluster dynamics allows us to depict a phase diagram depending on the number of agents in the arena and the excitation intensity. To explain this, we introduce a simple kinetic model where cluster evolution is governed by a balance between adsorption and desorption processes. Interestingly, this simple model is able to reproduce the phase space observed experimentally.

Topologically ordered quantum matter exhibits intriguing long-range patterns of entanglement, which reveal themselves in subsystem entropies. However, measuring such entropies, which can be used to certify topological order, on large partitions is challenging and becomes practically unfeasible for large systems. We propose a protocol based on local adiabatic deformations of the Hamiltonian which extracts the universal features of long-range topological entanglement from measurements on small subsystems of finite size, trading an exponential number of measurements against a polynomial-time evolution. Our protocol is general and readily applicable to various quantum simulation architectures. We apply our method to various string-net models representing both Abelian and non-Abelian topologically ordered phases and illustrate its application to neutral atom tweezer arrays with numerical simulations.

Many-body fermionic systems can be simulated in a hardware-efficient manner using a fermionic quantum processor. Neutral atoms trapped in optical potentials can realize such processors, where nonlocal fermionic statistics are guaranteed at the hardware level. Implementing quantum error correction in this setup is, however, challenging, due to the atom-number superselection present in atomic systems, that is, the impossibility of creating coherent superpositions of different particle numbers. In this Letter, we overcome this constraint and present a blueprint for an error-corrected fermionic quantum processor that can be implemented using current experimental capabilities. To achieve this, we first consider an ancillary set of fermionic modes and design a fermionic reference, which we then use to construct superpositions of different numbers of referenced fermions. This allows us to build logical fermionic modes that can be error corrected using standard atomic operations. Here, we focus on phase errors, which we expect to be a dominant source of errors in neutral-atom quantum processors. We then construct logical fermionic gates, and show their implementation for the logical particle-number conserving processes relevant for quantum simulation. Finally, our protocol is illustrated with a minimal fermionic circuit, where it leads to a quadratic suppression of the logical error rate.

Using $e^{+}{e}^{-}$ data taken at the center-of-mass energy of 3.773 GeV with the BESIII detector, corresponding to an integrated luminosity of $20.3{\mathrm{fb}}^{-1}$, we report the first measurement of the decay dynamics of the semileptonic decays $D^{+(0)}\to K^{-}{\pi }^{+}{\pi }^{0(-)}{e}^{+}{\nu }_e$. The amplitude analysis gives the hadronic form factors of the semileptonic $D$ transitions into the axial-vector meson ${\overline{K}}_1(1270)$ to be $r_A=(-11.2\pm {1.0}_{\mathrm{stat}}\pm {0.9}_{\mathrm{syst}})\times {10}^{-2}$ and $r_V=(-4.3\pm {1.0}_{\mathrm{stat}}\pm {2.5}_{\mathrm{syst}})\times {10}^{-2}$. This is the first in the semileptonic decays of heavy mesons into axial-vector mesons. The angular analysis yields an up-down asymmetry ${\mathcal{A}}_{\mathrm{ud}}^{\prime }=0.01\pm 0.11$, which is consistent with the standard model prediction. In addition, the branching fractions of $D^{+}\to {\overline{K}}_1(1270{)}^0{e}^{+}{\nu }_e$ and $D^0\to K_1(1270{)}^{-}{e}^{+}{\nu }_e$ are determined with improved precision to be $(2.27\pm 0.11_{\mathrm{stat}}\pm 0.07_{\mathrm{syst}}\pm 0.07_{\text{input}})\times {10}^{-3}$ and $(1.02\pm 0.06_{\mathrm{stat}}\pm 0.06_{\mathrm{syst}}\pm 0.03_{\text{input}})\times {10}^{-3}$, respectively. No significant signals of $D^{+}\to {\overline{K}}_1(1400{)}^0{e}^{+}{\nu }_e$ and $D^0\to K_1(1400{)}^{-}{e}^{+}{\nu }_e$ are observed and their branching fraction upper limits are set as $1.4\times {10}^{-4}$ and $0.7\times {10}^{-4}$ at 90% confidence level, respectively.

A measurement is presented of the cross section in proton-proton collisions for the production of two $W$ bosons and one $Z$ boson. It is based on data recorded by the CMS experiment at the CERN LHC at center-of-mass energies $\sqrt{s}=13$ and 13.6 TeV, corresponding to an integrated luminosity of $200{\mathrm{fb}}^{-1}$. Events with four charged leptons (electrons or muons) in the final state are selected. Both nonresonant $WWZ$ production and $ZH$ production, with the Higgs boson decaying into two $W$ bosons, are reported. For the first time, the two processes are measured separately in a simultaneous fit. Combining the two modes, signal strengths relative to the standard model (SM) predictions of ${0.75}_{-0.29}^{+0.34}$ and ${1.74}_{-0.60}^{+0.71}$ are measured for $\sqrt{s}=13$ and 13.6 TeV, respectively. The observed (expected) significance for the triboson signal is 3.8 (2.5) standard deviations for $\sqrt{s}=13.6\mathrm{TeV}$, thus providing the first evidence for triboson production at this center-of-mass energy. Combining the two modes and the two center-of-mass energies, the inclusive signal strength relative to the SM prediction is measured to be ${1.03}_{-0.28}^{+0.31}$, with an observed (expected) significance of 4.5 (5.0) standard deviations.

Bound states of charm and anticharm quarks, known as charmonia, have a rich spectroscopic structure that can be used to probe the dynamics of hadron production in high-energy hadron collisions. Here, the cross section ratio of excited $(\psi (2S))$ and ground state $(J/\psi )$ vector mesons is measured as a function of the charged-particle multiplicity in proton-lead ($p\mathrm{Pb}$) collisions at a center-of-mass (CM) energy per nucleon pair of 8.16 TeV. The data corresponding to an integrated luminosity of $175{\mathrm{nb}}^{-1}$ were collected using the CMS detector. The ratio is measured separately for prompt and nonprompt charmonia in the transverse momentum range $6.5<p_{\mathrm{T}}<30\mathrm{GeV}$ and in four rapidity ranges spanning $-2.865<y_{\mathrm{CM}}<1.935$. For the first time, a statistically significant multiplicity dependence of the prompt cross section ratio is observed in proton-nucleus collisions. There is no clear rapidity dependence in the ratio. The prompt measurements are compared with a theoretical model which includes interactions with nearby particles during the evolution of the system. These results provide additional constraints on hadronization models of heavy quarks in nuclear collisions.