Storage and retrieval refer to the task of encoding an unknown quantum channel $\mathrm{\Lambda }$ into a quantum state, known as the program state, such that the channel can later be retrieved. There are two strategies for this task: classical and quantum strategies. The classical strategy uses multiple queries to $\mathrm{\Lambda }$ to estimate $\mathrm{\Lambda }$ and retrieves the channel based on the estimate represented in classical bits. The classical strategy turns out to offer the optimal performance for the storage and retrieval of unitary channels. In this work, we analyze the asymptotic performance of the classical and quantum strategies for the storage and retrieval of isometry channels. We show that the optimal fidelity for isometry estimation is given by $F=1-[d(D-d)/n]+O(n^{-2})$, where $d$ and $D$ denote the input and output dimensions of the isometry, and $n$ is the number of queries. This result indicates that, unlike in the case of unitary channels, the classical strategy is suboptimal for the storage and retrieval of isometry channels, which requires $n=\mathrm{\Theta }({\epsilon }^{-1})$ to achieve the diamond-norm error $\epsilon$. We propose a more efficient quantum strategy based on port-based teleportation, which stores the isometry channel in a program state using only $n=\mathrm{\Theta }(1/\sqrt{\epsilon })$ queries, achieving a quadratic improvement over the classical strategy. As an application, we extend our approach to general quantum channels, achieving improved program cost compared to prior results by Gschwendtner, Bluhm, and Winter [Quantum 5, 488 (2021)].

The solar system currently traverses the Local Interstellar Cloud (LIC), one of several warm cloudlets of the Complex of Local Interstellar Clouds (CLIC) in the solar neighborhood. The origin of these cloudlets is unknown and could be related to supernova shock wave dynamics. If supernovae are the source of these cloudlets or influence their properties, the CLIC may act as a cosmic archive for the supernova-produced radionuclide ${}^{60}\mathrm{Fe}$. We detected minuscule traces of interstellar ${}^{60}\mathrm{Fe}$ in 295 kg of the European Project for Ice Coring in Antarctica Dronning Maud Land ice core, covering the time period 40–81 kyr ago. We find an ${}^{60}\mathrm{Fe}/{}^{53}\mathrm{Mn}$ ratio of $(8\pm 5)\times {10}^{-4}$, slightly above the expected cosmogenic production, corresponding to an interstellar deposition rate of (${0.22}_{-0.12}^{+0.14}$) ${}^{60}\mathrm{Fe}$ $\mathrm{at}/{\mathrm{cm}}^2/\mathrm{yr}$. This influx is significantly lower than that observed in recent Antarctic snow and marine sediment records during the last 40 kyr. These results suggest that the LIC is a cosmic archive for supernova-produced ${}^{60}\mathrm{Fe}$. The imprinted ${}^{60}\mathrm{Fe}$ time profile is evidence for a changing local interstellar environment over the last 80 kyr.

Achieving invisibility in diffusive fields with metamaterials has long been hindered by a fundamental trade-off: suppressing external scattering by means of a metamaterial shell inevitably distorts the shell’s internal field, precluding perfect transparency. We overcome this limitation by introducing a dual-zero-scattering regime that simultaneously eliminates scattering in both the background medium and the metamaterial shell. Through a unified theoretical framework that integrates coordinate transformation with scattering cancellation, we demonstrate this concept both numerically and experimentally in thermal sensors, cloaks, and concentrators. The required shell’s anisotropic thermal conductivity is realized using deep-learning-optimized microstructures. This approach establishes a general paradigm for designing truly noninvasive devices in diffusion-based systems, with promising extensions to wave phenomena such as acoustics and electromagnetics.

A background-free intensity autocorrelation measurement for 10-keV femtosecond x-ray pulses is demonstrated using x-ray second harmonic generation. The narrow phase-matching condition of x-ray second harmonic generation allows for the selective generation of either the autocorrelation or background signals in a quasicollinear geometry with a crossing angle of $\sim 300\mathrm{\mu }\mathrm{rad}$, achieving a geometric time resolution of $\sim 1$ attosecond. The measured autocorrelation traces exhibit zero background and clearly reveal temporal modifications through an Si(311) monochromator, verifying x-ray temporal shaping with perfect crystals. The applicability of this method to attosecond x-ray pulses is also discussed.

Coulomb interactions deeply affect quantum transport in simple ballistic systems, but their impact on scaled up ballistic structures remains underexplored. Here, we theoretically consider a chain of small metallic dots with frozen charge dynamics connected by ballistic channels. We identify a neutral mode of transport that is specific to a chain with at least two islands and entwines local diffusion by neutral excitations with long-range correlations between the islands’ charge states. We show, as an experimentally measurable signature of this many-body behavior, that the Wiedemann-Franz law is violated with a Lorenz ratio scaling as the square root of the chain’s length.

The surprisingly rich physics of a single Coulomb-blockaded metallic island coupled to quantum Hall edge channels is now well established, giving rise to exotic quantum impurity states. Here, we show that qualitatively new physics emerges in arrays of such elements. Universal and robust behavior emerges for energy scales smaller than the charging energy of the islands. We consider a chain of $N$ metallic islands and find that it displays nonlocal responses. In particular, we demonstrate that for the bulk filling factor of $\nu =1$, the islands could support a finite heat flow without a temperature difference between them. Upon pinching the array with a quantum point contact, we predict an entropy change that scales with the number of islands as $\mathrm{\Delta }S=\frac{1}{2}{k}_B\log (N+1)$.

Topological solitons hold great promise for revolutionizing information and energy technologies, yet their controlled creation remains a major challenge. Here, we demonstrate room-temperature nucleation of fractional, skyrmion loops—three-dimensional, half-integer topological defects—within a nematic liquid crystal microfluidic cell. A single beam of linearly polarized light rotates the surface alignment, accumulating elastic twist until a topologically trivial texture collapses into a robust skyrmion loop. The loop’s cross section continuously morphs between half Néel skyrmions, antiskyrmions, and bimerons. Real-time polarized microscopy and Landau–de Gennes free energy based simulations reveal that the transition occurs via a $2\pi$ twist discontinuity and a sharp energy drop. The same protocol can be triggered by electric fields or local heating, and spawns a pair of $\pm 1$ topological monopoles that migrate along the loop to minimize the free energy. Our findings establish nematic liquid crystals as an optically rewritable, low-energy platform for generating arbitrary three-dimensional topological textures, offering immediate avenues for reconfigurable photonics and topological metamaterials.

In this Letter, we present a compelling and robust argument for the roles of neutrino fast flavor conversion (FFC) in the explosion mechanism of core-collapse supernova (CCSN), combining the multiangle FFC subgrid model rooted in quantum kinetic theory with the multidimensional four-species Boltzmann neutrino radiation hydrodynamics. Employing various progenitor masses and the nuclear equations of states, we find that the effect of FFC on CCSN explosion is bifurcated depending on the progenitors. For the lowest-mass progenitor, FFC facilitates the shock revival and enhances the explosion energy, whereas for higher-mass progenitors its impact is inhibitory. We identify the mass accretion rate as the key determinant governing this bifurcation. When the mass accretion rate is low (high), the contribution of FFC to neutrino heating becomes positive (negative) because the heating efficiency enhancement via FFC-driven spectral hardening of electron-type neutrinos dominates over (is outweighed by) the concurrent reduction in neutrino luminosity. Our results further highlight the limitations of approximate neutrino transport and demonstrate that a multiangle treatment is essential for accurately capturing FFC effects; otherwise, FFCs are missed and even generated spuriously.

Pancharatnam-Berry (PB) metasurfaces encode the geometric phase through the rotation of the meta-atom, which exhibits opposite phases and nearly equal conversion amplitudes in the two cross-polarized channels. This spin duality has long restricted PB metasurfaces to spin-symmetric responses with insufficient contrast for spin-selective operation. Here we experimentally demonstrate a regime in which the geometric phase is preserved while its spin duality is deliberately broken. By engineering the pillar-lattice symmetry mismatch together with the etch depth to maximize contrast, we decouple the conversion amplitudes of the two spin channels without affecting the geometric-phase evolution. This enables a spin-asymmetric geometric-phase response that has not been accessible in conventional PB designs. We verify the broken duality through far-field measurements that reveal the selective suppression of the conjugate channel normally enforced by the PB phase. These results establish an accessible pathway to geometric-phase metasurfaces operating beyond their long-standing spin-duality constraint, enabling new forms of spin-dependent wavefront control in optical communications and displays with flat-optical elements.

Energy loss of fast electrons in materials is a fundamental process in many fields spanning fusion research, high-energy-density physics, astrophysics, and material science. Contrary to conventional collisional theory that predicts greater energy loss in denser materials, we experimentally observe an anomalous phenomenon: high-current-density electron beams undergo significantly stronger deflection and stopping in low-average-density porous foams than in their denser counterparts. Pore-resolved simulations and theoretical analysis demonstrate that return currents along the foam’s skeleton generate multi-kilo-Tesla magnetic fields in the vacuum pores. These intense fields strongly scatter beam electrons, enhancing stopping by orders of magnitude beyond collisional predictions. The derived conditions for this anomalous stopping agree with experiments and simulations, establishing a new microstructure-mediated regime of beam-matter interaction with potential applications in charged-beam control for fusion and laboratory astrophysics.

Motility-induced phase separation (MIPS) is a central collective phenomenon in active matter, theoretically established in the overdamped regime. We discover that the dynamical origin of MIPS is fundamentally altered by inertia, which induces a cooling mechanism absent in overdamped active matter. This conclusion is supported by an active variant of the direct simulation Monte Carlo method and by a kinetic theory for inertial self-propelled hard spheres derived from the microscopic dynamics. In contrast to the overdamped case, both analyses demonstrate that inertial MIPS can occur even without impenetrability, as it originates from a density-dependent cooling mechanism due to the coupling of density, orientation, and temperature. This mechanism emerges from the competition between activity and a density-dependent collision rate arising from spatial correlations between colliding particles. These findings open a pathway to fundamentally connect inertial active matter with granular physics.

We report the first detection of gamma-ray emission up to ultrahigh-energy (UHE; $>100\mathrm{TeV}$) emission from the prototypical gamma-ray binary system LS I $+61°$ 303 using data from the Large High Altitude Air Shower Observatory. It is detected with significances of $9.2\sigma$ in the Water Cherenkov Detector Array (WCDA, $1.4-30.5\mathrm{TeV}$) and $6.2\sigma$ in the Kilometer Square Array (KM2A, $25-267\mathrm{TeV}$); in KM2A alone we identify 16 photonlike events above 100 TeV against an estimated 5.1 background events, corresponding to a $3.8\sigma$ detection. These results provide compelling evidence of extreme particle acceleration in LS I $+61°$ 303. Furthermore, we observe orbital modulation at $3.9\sigma$ confidence level, between 25 and 100 TeV, with a hint that the orbital modulation is energy dependent. These features can be understood in a composite scenario in which leptonic and hadronic processes jointly contribute.

The Arrhenius model has long provided a framework for describing thermally activated processes in solids, linking temperature to relaxation dynamics through a fixed activation barrier. Yet in molecular glasses, it routinely produces unphysically low preexponential factors, ${\tau }_0^{*}$, raising fundamental questions about the physical meaning of the extracted parameters. Here, we resolve this long-standing paradox by showing that the activation energy decreases linearly with temperature as a consequence of density-driven variations of the barrier. Using a constant-volume approach combining broadband dielectric spectroscopy with pressure-volume-temperature analysis, we separate thermal and density contributions and directly quantify energy barriers. The results confirm theoretical predictions made fifty years ago but never experimentally verified. Neglecting the temperature dependence of activation energy systematically inflates barrier heights and drives anomalously low ${\tau }_0^{*}$ in conventional Arrhenius fits, leading to misleading conclusions about glassy dynamics. This effect is observed for both intramolecular secondary relaxations and intermolecular processes of the Johari-Goldstein relaxation type, highlighting the generality of the mechanism. Our Letter sets a new standard for interpreting secondary relaxation processes and provides a physically justified framework for analyzing thermally activated dynamics across a wide range of amorphous materials.

Mechanical modulation of recoilless nuclear transitions allows the dynamic control of $\gamma$-ray emission and absorption. Accessing modulation frequencies well above the nuclear linewidth enables coherent manipulation of the nuclear response. Here we demonstrate high-frequency control via efficient coupling of a film of enriched ${}^{57}\mathrm{Fe}$ to a 97.9 MHz surface acoustic wave, nearly 2 orders of magnitude higher than the nuclear linewidth. The mechanical drive produces a comb of absorption sidebands in the Mössbauer spectrum, reflecting the periodic time modulation of the nuclear transitions. This constitutes the highest frequency mechanically driven Mössbauer resonance to date. Our solid-state, monolithic platform establishes a new interface between nuclear transitions and high-frequency acoustics, with applications in $\gamma$-ray quantum optics and precision nuclear spectroscopy.

Proximity effects complement conventional materials design by enabling interfacial properties absent in any constituent. Here, we uncover an altermagnetic proximity effect (AMPE), distinct from ferromagnetic and antiferromagnetic proximity, in which the hallmark momentum-alternating spin splitting of an altermagnet is transferred across an interface into an adjacent nonmagnetic layer—a process we term “altermagnetization.” Using first-principles calculations and model analysis, we identify the AMPE in heterostructures based on the prototypical van der Waals altermagnet ${\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$, where a proximitized monolayer PbO acquires altermagnetic band splitting and real-space spin textures, with systematic tunability via interlayer spacing and magnetic configuration. We further demonstrate that the AMPE enables valley-dependent spin splitting in the semiconductor PbS and realizes topological superconductivity in the $s$-wave superconductor ${\mathrm{NbSe}}_2$, both inheriting the altermagnetic spin texture. Finally, we validate the generality and experimental feasibility of the AMPE by realizing it in a broader class of established altermagnets, including ${\mathrm{V}}_2{\mathrm{Se}}_2\mathrm{O}$ derivatives, Ruddlesden-Popper perovskites, and the metallic CrSb. Our results identify the AMPE as a universal proximity mechanism and a versatile platform for engineering emergent quantum phenomena in heterostructures.

Quantum communication in the microwave regime is set to play an important role in distributed quantum computing and hybrid quantum networks. However, typical superconducting quantum circuits require millikelvin temperatures for operation, which poses a significant challenge for large-scale microwave quantum networks. Here, we present a solution to this challenge by demonstrating the successful quantum teleportation of microwave coherent states between two spatially separated dilution refrigerators over a thermal microwave channel in the temperature range up to 4 K. We distribute two-mode squeezed states over this noisy channel and employ the resulting quantum entanglement for quantum teleportation of coherent states with fidelities of $72.3\pm 0.5\%$ at 1 K and $59.9\pm 2.5\%$ at 4 K, exceeding the no-cloning and classical communication thresholds, respectively. We successfully model the teleportation protocol using a Gaussian operator formalism that includes losses and noise. Our analysis shows that the teleportation infidelity mainly stems from a parasitic heating of the cold quantum nodes due to the hot network connection. These results demonstrate the experimental feasibility of distributed superconducting architectures and motivate further investigations of noisy quantum networks in various frequency regimes.

The Shastry-Sutherland model is an effective model of the layered material ${\mathrm{SrCu}}_2({\mathrm{BO}}_3{)}_2$, which exhibits an extremely rich phase diagram as a function of pressure and magnetic field. Motivated by the recent controversy regarding its phase diagram at zero magnetic field, we perform large-scale simulations based on infinite projected entangled-pair states, a two-dimensional tensor network Ansatz to represent the ground state directly in the thermodynamic limit. By employing the latest optimization techniques, we obtain variational states with lower energy than previous results obtained from other methods. Using systematic extrapolations to the exact infinite bond dimension limit, our simulations reveal a narrow quantum spin liquid phase between the plaquette and antiferromagnetic phases in the range $0.785(5)\le J^{\prime }/J\le 0.82(1)$.

We demonstrate numerically the existence of solutions of five-dimensional vacuum gravity describing the formation, in finite time, of an extremal rotating black hole from a preexisting Schwarzschild black hole. This is the first example of a violation of the third law of black hole mechanics in vacuum gravity and demonstrates that the third law is false independently of any matter model. We also demonstrate the existence of solutions describing the formation, in finite time, of an extremal rotating black hole from vacuum initial data that do not contain a black hole.

We report local conductivity imaging of edge states in monolayer graphene by millikelvin microwave impedance microscopy. At the charge-neutrality point, as the magnetic field increases, the local conductivity at the edge drops to zero more slowly than in the bulk. This behavior is consistent with the calculated spatial profile of the charge gap in the canted antiferromagnetic phase. For comparison, we also perform microwave imaging of integer quantum Hall states away from neutrality, which host dissipationless chiral edge channels. The evolution of the edge signal as a function of the bulk gap is fundamentally different between the Landau level filling factor $\nu =0$ and $|\nu |\ge 1$ integer quantum Hall states, which can be qualitatively explained by numerical simulations and theoretical analysis. Our results provide a comprehensive microscopic picture of the edge and bulk states as the Fermi level moves across the unique Landau-level spectrum of graphene.

The Fermilab E906/SeaQuest collaboration performed measurements of the Drell-Yan process using 120 GeV proton beams bombarding liquid hydrogen and liquid deuterium targets. A combined analysis of all collected data was performed to obtain the final results for the ${\sigma }_{pd}/2{\sigma }_{pp}$ Drell-Yan cross section ratio covering the kinematic region of $0.13<x<0.45$. The $x$ dependencies of $\overline{d}(x)/\overline{u}(x)$ and $\overline{d}(x)-\overline{u}(x)$ are extracted from these cross section ratios. It is found that $\overline{d}(x)$ is greater than $\overline{u}(x)$ over the entire measured $x$ range, with improved statistical accuracy compared to previous measurements. The new results on $\overline{d}(x)/\overline{u}(x)$ and $\overline{d}(x)-\overline{u}(x)$ are compared to various parton distribution functions and theoretical calculations.