Quantum thermodynamics studies how quantum systems and operations may be exploited as sources of work to perform useful thermodynamic tasks. In real-world conditions, the evolution of open quantum systems typically displays memory effects, resulting in a non-Markovian dynamics. The associated information backflow has been observed to provide advantage in certain thermodynamic tasks. However, a general operational connection between non-Markovianity and thermodynamics in the quantum regime has remained elusive. Here, we analyze the role of non-Markovianity in the central task of extracting work via thermal operations from general multitime quantum processes, as described by process tensors. By defining a hierarchy of four classes of extraction protocols, expressed as quantum combs, we reveal three different physical mechanisms (work investment, multitime correlations, and system-environment correlations) through which non-Markovianity increases the work distillable from the process. The advantages arising from these mechanisms are linked precisely to a quantifier of the non-Markovianity of the process. These results show in very general terms how non-Markovianity of any given quantum process is a fundamental resource that unlocks an enhanced performance in thermodynamics.

We propose a quantum measurement that probabilistically projects a pair of qudits of dimension $d$ onto a Bell state in a two-qubit subspace. It can be implemented using linear-optical circuits with the success probabilities of $1-d^{-1}$ without ancilla photons and $1-d^{-(k+1)}$ with $2(2^k-1)$ ancilla photons. It allows us to entangle two independently prepared high-dimensional entangled states two dimensionally with higher success probabilities than ones of linear-optical fusion gates on qubits. As an application, we propose a fast quantum repeater protocol with three-qudit GHZ states and quantum memories.

We report new constraints on axionlike particles (ALPs) using data from the NEON experiment, which features 16.7 kg of NaI(Tl) target located 23.7 m from a 2.8 GW thermal power nuclear reactor. Analyzing a total exposure of $3063\mathrm{kg}·\mathrm{day}$, with $1596\mathrm{kg}·\mathrm{day}$ during reactor-on and $1467\mathrm{kg}·\mathrm{day}$ during reactor-off periods, we compared energy spectra to search for ALP-induced signals. No significant signal was observed, enabling us to set exclusion limits at the 95% confidence level. These limits probe previously unexplored regions of the ALP parameter space, particularly for axion masses (${\mathrm{m}}_a$) near $1\mathrm{MeV}/{\mathrm{c}}^2$. For ALP-photon coupling ($g_{a\gamma }$), limits reach as low as $6.24\times {10}^{-6}{\mathrm{GeV}}^{-1}$ at ${\mathrm{m}}_a=3.0\mathrm{MeV}/{\mathrm{c}}^2$, while for ALP-electron coupling ($g_{ae}$), limits reach $4.95\times {10}^{-8}$ at ${\mathrm{m}}_a=1.02\mathrm{MeV}/{\mathrm{c}}^2$. This Letter demonstrates the potential for future reactor experiments to probe unexplored ALP parameter space.

We present a novel approach to constructing gravitational instantons based on the observation that the gravitational action of general relativity in its teleparallel formulation can be expressed as a product of the torsion and excitation forms. We introduce a new class of solutions where these two forms are equal, which we term the self-excited instantons, and advocate for their use over the self-dual instantons of Eguchi and Hanson. These new self-excited instantons exhibit striking similarities to BPST instantons in Yang-Mills theory, as their action reduces to a topological Nieh-Yan term, which allows us to identify the axial torsion as a topological current and show that the gravitational action is given by a topological charge.

A precise evaluation of the electroweak contribution to the anomalous magnetic moment of the muon requires control over all aspects of the standard model, ranging from Higgs physics, over multiloop computations for bosonic and (heavy-)fermion diagrams, to nonperturbative effects in the presence of light quarks. Currently, the dominant uncertainties arise from such hadronic effects in the vector–vector–axial-vector three-point function, an improved understanding of which has recently emerged in the context of hadronic light-by-light scattering. Profiting from these developments as well as new perturbative and nonperturbative input for the charm contribution, we obtain $a_{\mu }^{\mathrm{EW}}=154.4(4)\times {10}^{-11}$.

How long an electron spends under the barrier during strong field tunneling ionization is still a controversial issue in attosecond science. We develop a new attoclock technique to address this problem. It exploits the carrier-envelope-phase dependence of angular streaking to extrapolate from elliptically polarized light measurements, for the first time, the deflection angles for circularly polarized light. Thus, we can avoid the ambiguity inherent to the modeling of the conventional elliptical attoclock. Our results show that the deflection angles are solely sensitive to the ionization potentials of targets and tunneling delay is a minor effect.

Metal-containing molecular ions are fundamentally important in both terrestrial and interstellar chemistry, yet their formation mechanisms have been largely unexplored experimentally. To address this lack of fundamental understanding of how these ions are created in space, we conducted an experimental study of a quantum-state-controlled reaction between ${\mathrm{Ca}}^{+}$ and ${\mathrm{C}}_2{\mathrm{H}}_2$ to investigate a potential unifying mechanism for the formation of metallic molecules. By tuning the quantum-state populations of laser-cooled ${\mathrm{Ca}}^{+}$, we demonstrate precise control over reactivity. Our results reveal a single ionic product, ${\text{CaCCH}}^{+}$, providing valuable insights into the mechanisms underlying the formation of metal-containing ions in space.

Identifying conservation laws is central to every subfield of physics, as they illuminate the underlying symmetries and fundamental principles. A prime example can be found in quantum optics: the conservation of orbital angular momentum (OAM) during spontaneous parametric down-conversion (SPDC) enables the generation of a photon pair with entangled OAM. In this Letter, we report on the observation of OAM conservation in SPDC pumped on the single-photon level by a preceding SPDC process. We implement this cascaded down-conversion scheme in free space, without waveguide confinement, and thereby set the stage for experiments on the direct generation of multiphoton high-dimensional entanglement using all degrees of freedom of light.

While the spontaneous emission from independent emitters provides spatially uncorrelated photons—a typical manifestation of quantum randomness, the interference of the coherent scattering leads to a well-defined intensity pattern—a feature described by linear optics. We here demonstrate experimentally how the interplay between the two mechanisms in large systems of quantum emitters leads to spatial variations of photon correlations. The implementation with trapped ion crystals in free space allows us to observe the anticorrelation between photon rates and variance of the photon number distributions in chains of up to 18 ions. For smaller crystals of four ions, the transition from antibunching to bunching and super-Poissonian statistics of the scattered light is reported. For higher numbers of scatterers, the photon statistics still display a strong deviation from the fully incoherent scattering case. Our results illustrate how the interference of coherent scattering, combined with spontaneous emission, provides a control mechanism for the light statistics.

Photonic Ising machines constitute an emergent new paradigm of computation geared toward tackling combinatorial optimization problems that can be reduced to the problem of finding the ground state of an Ising model. Spatial photonic Ising machines (SPIMs) have proven advantageous for simulating fully connected large-scale spin systems. Fine control of a general interaction matrix $J$ has been accomplished so far only through matrix decomposition methods. We introduce and experimentally validate a SPIM instance that enables direct control over the full interaction matrix, allowing the encoding of Ising Hamiltonians with arbitrary couplings and connectivity. We demonstrate the conformity of the experimentally measured Ising energy with the theoretically expected value and then proceed to solve both the unweighted and weighted graph partitioning problems, showcasing a systematic convergence to an optimal solution via simulated annealing. Our approach significantly expands the applicability of SPIMs for real-world applications, as it is more efficient than matrix decomposition methods in the case of sparse problems. It paves the way to encoding the full range of NP problems that are known to be equivalent to Ising models on SPIM devices.

We propose and theoretically demonstrate a technique that allows one to compensate for chromatic aberrations of traditional electron lenses in ultrafast electron microscopes. The technique is based on space- and time-dependent phase modulation of a pulsed electron beam using interaction with a shaped pulsed ponderomotive lens. The energy-selective focal distance is reached by combining the electron temporal chirp with the time-dependent size of the effective potential, with which the electrons interact. As a result, chromatic aberration can be reduced by up to a factor of 7. This approach paves the way for advanced transverse and longitudinal wave front shaping of electrons in free space.

We study the self-organization of turbulence in a geophysically motivated two-dimensional fluid with local interactions. Using simulations and theory, we show that the out-of-equilibrium flux to small scales imposes a constraint on the large-scale emergent flow. Consequently, a rich phase diagram of large-scale configurations emerges, replacing the unique state found in flows with energy injection below the interaction scale. We explain what sets the boundaries between the different phases and the occurrence of spontaneous symmetry breaking. This letter demonstrates that the selection mechanism of large-scale structures in quasigeostrophic flows can be dramatically altered by forcing above the interaction scale.

Multiple topologically distinct quantum Hall phases can occur at the same Landau level filling factor. It is a major challenge to distinguish between these phases as they only differ by the neutral modes, which do not affect the charge conductance in conventional geometries. We show that the neutral sector can be determined with coherent charge conductance in a $\pi$-shaped geometry that interfaces three different filling factors. Specifically, non-Abelian paired states at a half-filled Landau level and the anti-Read-Rezayi state can be identified. Interestingly, for interfaces between paired states and Jain states, the electric current in the $\pi$ geometry behaves as if pairs of neutral Majorana edge modes were charge modes of Jain states.

Natural orbital functional (NOF) theory provides a valuable framework for studying strongly correlated systems at an affordable computational cost, with an accuracy comparable to highly demanding wave-function-based methods. However, its widespread adoption in cases involving a large number of correlated electrons has been limited by the extensive iterations required for convergence. In this Letter, we present an approach that integrates the techniques used for optimization in deep learning into NOF calculations, enabling a substantial expansion in the scale of accessible systems. The proposed procedure employs an adaptive momentum-based technique for orbital optimization, alternated with the optimization of occupation numbers, significantly improving the computational feasibility of challenging calculations. We illustrate the capabilities of our approach through three challenging test cases: (i) the symmetric dissociation of a large hydrogen cluster with 1000 electrons, (ii) an analysis of occupancy distributions in fullerenes, and (iii) a study of the singlet-triplet energy gap in linear acenes. These examples demonstrate the method’s applicability to large-scale systems and strongly correlated electron phenomena, extending the reach of NOF theory to increasingly complex systems.

Superconductivity usually emerges from a metallic normal state which follows the Fermi-liquid paradigm. If, in contrast, the normal state is a fractionalized non-Fermi liquid, then pairing may either eliminate fractionalization via a Higgs-type mechanism leading to a conventional superconducting state, or pairing can occur in the presence of fractionalization. Here, we discuss a simple model for the latter case: using a combination of perturbation theory and functional renormalization group, we show that the Kitaev-Kondo lattice model displays a fractionalized superconducting phase at weak Kondo coupling. This phase is characterized by Cooper pairing of conventional electronic quasiparticles, coexisting with a spin-liquid background and topological order. Depending on the sign of the Kitaev coupling, we find the pairing to be either of chiral $d$-wave or $p$-wave type for extended doping regions around the van Hove filling. We discuss applications and extensions.

Phonon nonreciprocity, indicating different transport properties along opposite directions, has been observed in experiments under a magnetic field. We show that nonreciprocal acoustic phonons can also exist without a magnetic field or net magnetization. We identify crucial contributions in phenomenological elastic theory. In $\mathcal{P}\mathcal{T}$ symmetric antiferromagnets, we find two terms, dubbed flexo viscosity and flexo torque, that induce phonon nonreciprocity. The microscopic origin of these terms is attributed to the derivatives of molecular Berry curvature, manifested as emergent nonlocal magnetic fields on phonons. The symmetry breaking that originated from spin order is transferred to the phonon system through spin-orbit coupling, where the orbital degree of freedom affects the lattice dynamics directly. By electrically breaking inversion symmetry and modifying the spin-orbit coupling, we find extra contributions and show that both the phonon nonreciprocity and helicity can be controlled and enhanced. Importantly, the phonon nonreciprocity is an odd function of the Néel vector, serving as an indicator of the order parameter.

We report on tip-enhanced Raman spectroscopy of ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ molecules physisorbed within a plasmonic picocavity at 10 K. The intense Raman peaks resulting from the rotational and vibrational transitions are observed at subnanometer gap distances of the junction formed by an Ag tip and an Ag(111) surface, where a picocavity-enhanced field plays a crucial role. A significant redshift of the H-H stretch frequency is observed as the gap distance decreases, while the D-D stretch frequency is unaffected. Density functional theory, path-integral molecular dynamics, and quantum anharmonic vibrational energy calculations suggest that this unexpected isotope effect is explained by a different molecular density between ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ on the surface.

The effect of hydrodynamic interactions on the nonequilibrium stochastic dynamics of particles—arising from the conservation of momentum in the fluid medium—is examined in the context of the relationship between fluctuations, response functions, and the entropy production rate. The multiplicative nature of the hydrodynamic interactions is shown to introduce subtleties that preclude a straightforward extension of the Harada-Sasa relation. A generalization of the definitions involved in the framework is used to propose a new form of the relation applicable to systems with hydrodynamic interactions. The resulting framework will enable characterization of the nonequilibrium properties of living and active matter systems, which are predominantly in suspensions.