Perfect absorption of light critically affects light-matter interaction for various applications. Coherent perfect absorbers (CPAs) gain the unique capability of controlling light with light in a linear fashion. Multicolor CPAs [S. Longhi, Time-reversed optical parametric oscillation, Phys. Rev. Lett. 107, 033901 (2011)] are highly desirable for broadband and nonlinear light-to-light coherent control but the experimental demonstration has still remained elusive. Here, for the first time, we experimentally observe a dual-color version of a CPA (DC-CPA) through a second harmonic generation in a single whispering-gallery-mode microcavity. The DC-CPA enables simultaneous perfect absorption of both the incoming fundamental wave and its second harmonic. Similar to its linear counterpart, coherent control in the DC-CPA can also be realized by tuning the relative phase and intensity between the two-colored waves through nonlinear interference instead of the linear one. This scheme breaks the linear boundary of the traditional CPA into a multifrequency domain and paves the way toward all-optical signal processing and quantum information.

We show that bodies with two planes of symmetry can display a range of behaviors even without inertia. Any such body supports a conserved quantity in its dynamics, and is either a settler, a drifter or a flutterer, depending only on its shape. At large time, settlers and drifters, respectively, fall vertically and obliquely, while flutterers rotate forever while executing intricate patterns. The dynamics of flutterers decouples into a periodic and a Floquet part with different timescales, giving periodicity or quasiperiodicity. We design a set of bodies and use the boundary integral method to show that settlers, drifters, and flutterers, all lie in this set.

Orientational order is a common feature of many biological and synthetic materials. Topological defects are discontinuities in this order that are often coupled to geometric features of the materials. Here, we study the equilibrium shapes of fluid membranes featuring a $+1$ topological defect as a model for morphogenesis. We show, through simulation and analytic calculation, that the membrane can spontaneously deform toward a conical shape with a defect at its apex. We show that the relative stability of the deformation is controlled by the balance of the elastic parameters. When boundary constraints are introduced, we observe three distinct modes of deformation. These deformation modes take advantage of the way in which splay, twist, and bend distortions of the director field can be exchanged on a curved surface. Finally, we demonstrate inverted solutions. Our findings demonstrate a mechanism for passive defect driven morphogenesis as well as the fusion of $+1/2$ topological defect pairs on deformable surfaces.

We show that the maximum extractable work (ergotropy) from a quantum many-body system is constrained by “local athermality” of an initial state and “local entropy decrease” brought about by quantum operations. The obtained universal upper bound on ergotropy implies that the eigenstate thermalization hypothesis prohibits work extraction from energy eigenstates by means of finite-time unitary operations. This no-go property implies that Planck’s principle, a form of the second law of thermodynamics, holds even for pure quantum states. Our result bridges two independently studied concepts of quantum thermodynamics, the second law and thermalization, via “intrasystem” correlations in many-body systems as a resource for work extraction.

We study the implementation of quantum engines and quantum heat pumps where the quantum adiabatic transformations are replaced by quantum Zeno strokes. During these strokes, frequent measurements are selectively performed on the external state of the system avoiding transition between different levels. This effectively delivers almost ideal isentropic transformations. We concentrate on the characterization of the performance of a quantum Zeno heat pump implemented with a quantum harmonic oscillator, showing that optimal performance can be achieved faster than with shortcut-to-adiabaticity techniques.

Simulation of quantum systems is notoriously challenging for classical computers, while quantum hardware is naturally well-suited for this task. However, the imperfections of contemporary quantum systems pose a considerable challenge in carrying out accurate simulations over long evolution times. Here, we experimentally demonstrate a method for quantum simulations on a small-scale trapped-ion–based quantum simulator. Our method enables quantum simulations of programmable spin-Hamiltonians, using only simple global fields, driving all qubits homogeneously and simultaneously. We measure the evolution of a quantum Ising ring and accurately reconstruct the Hamiltonian parameters, showcasing an accurate and high-fidelity simulation. Our method enables a significant reduction in the required control and depth of quantum simulations, thus generating longer evolution times with higher accuracy.

Shallow quantum circuits feature not only computational advantages over their classical counterparts but also cutting-edge applications. Storing quantum information generated by shallow circuits is a fundamental question of both theoretical and practical importance that remained largely unexplored. In this Letter, we show that $N$ copies of an unknown $n$-qubit state generated by a fixed-depth circuit can be compressed into a hybrid memory of $O(n{\log }_{2}N)$ (qu)bits, which achieves the optimal scaling of memory cost. Our work shows that the computational complexity of resources can significantly impact the rate of quantum information processing, offering a unique and unified view of quantum Shannon theory and quantum computing.

The hadronic vacuum polarization (HVP) contributions to the muon $g-2$ are the crucial quantity to resolve whether new physics is present or not in the comparison between the standard model (SM) prediction and experimental measurements at Fermilab. They are commonly and historically determined via dispersion relations using a vast catalogue of experimentally measured, low-energy $e^{+}{e}^{-}\to \text{hadrons}$ cross section data as input. These dispersive estimates result in a SM prediction that exhibits a muon $g-2$ discrepancy of more than $5\sigma$ when compared to experiment. However, recent lattice QCD evaluations of the HVP and a new hadronic cross section measurement from the CMD-3 experiment favor a no-new-physics scenario and, therefore, exhibit a common tension with the previous $e^{+}{e}^{-}\to \text{hadrons}$ data. This study explores the current and future implications of these two scenarios on other observables that are also sensitive to the HVP contributions in the hope that they may provide independent tests of the current tensions observed in the muon $g-2$.

Based on the scattering matrix method, we theoretically demonstrate that the chiral interaction can induce the almost perfect photon blockade (PB) in the waveguide-cavity quantum electrodynamics system. The mechanism relies on the multiphoton path’s interference within the waveguide, which is clearly shown by the analytic parameter regime for $g^{(2)}(0)\approx 0$. When $N$ cavities are introduced into the system, there are $N$ optimal parameter points accordingly for the almost perfect PB, where the required lowest chirality decreases exponentially with increasing $N$, and these optimal points are robust against disorder in the system’s frequencies. Under resonant driving and fixed chirality conditions, the output light depends solely on the parity of $N$ ($N\ge 2$), with a coherent state emerging for even numbers of cavities and a single-photon state for odd numbers. Our Letter offers an alternative route for achieving almost perfect PB effects with high single-photon transmission by employing the chirality of system, with potential application in the on-chip single-photon source with integrability.

We report an instability exhibited by a fluid system when coupling two distinct types of waves, both linearly damped. While none of them is unstable on its own, they amplify one another, resulting in a previously unreported convective instability. An external excitation is used to induce a parametric cross-coupling between longitudinal and transverse deformations of a liquid bridge between two vertical glass plates. Coherent amplification results in waves satisfying a synchronization condition, which selects a precise wavelength. We derive a model for this instability using depth-averaged Navier-Stokes equations, showing the physical origin of the coamplification, and confirm its relevance experimentally. Our findings open new perspectives in the study of parametrically controlled pattern formation, and invites the search for analogous parametric cross-coupling instabilities in other systems exhibiting distinct wave types, from plasma to elastic media.

In this work, building on state-of-the-art quantum Monte Carlo simulations, we perform systematic finite-size scaling of both entanglement and participation entropies for long-range Heisenberg chain with unfrustrated power-law decaying interactions. We find distinctive scaling behaviors for both quantum entropies in the various regimes explored by tuning the decay exponent $\alpha$, thus capturing nontrivial features through logarithmic terms, beyond the case of linear Nambu-Goldstone modes. Our systematic analysis reveals that the quantum entanglement information, hidden in the scaling of the two studied entropies, can be obtained to the same level of order parameters and other usual finite-size observables of quantum many-body lattice models. The analysis and results obtained here can readily apply to more quantum criticalities in 1D and 2D systems.

Topological magnetoelectricity was recently revealed as an emergent topic, which opens a unique route to precisely control magnetoelectric functionality. Here we report the synchronous magnetic-electric-cycle operation of topological magnetoelectric switching in ${\mathrm{GdMn}}_2{\mathrm{O}}_5$. Compared with pure magnetic-cycle operation, this topological winding can be accessed in a much broader parameter space, i.e., orientation of the magnetic field is not limited to the magic angle and the effect can persist up to the Curie temperature. The fine-tuning of the free energy landscape is responsible for this topological behavior.

Although optimal control (OC) has been studied in stochastic thermodynamics for systems with continuous state variables, less is known in systems with discrete state variables, such as chemical reaction networks (CRNs). Here, we develop a general theoretical framework to study OC of CRNs for changing the system from an initial distribution of states to a final distribution with minimum dissipation. We derive a “Kirchhoff’s law” for the probability current in the adiabatic limit, from which the optimal kinetic rates are determined analytically for any given probability trajectory allowed by local rate constraints. By using the optimal rates, we show that the total dissipation is determined by a $L_2$-distance measure in the probability space and derive an analytical expression for the metric tensor that depends on the probability distribution, network topology, and capacity of each link. Minimizing the total dissipation leads to the geodesic trajectory in the probability space and the corresponding OC protocol is determined by the Kirchhoff’s law. To demonstrate our general approach, we use it to find a lower bound for the minimum dissipation that is tighter than existing bounds obtained with only global constraints in the adiabatic limit. We also apply it to simple networks, e.g., fully connected three-state CRNs with different local constraints and show that indirect pathway and nonfunctional transient state can play a crucial role in switching between different probability distributions efficiently. Future directions in studying OC in CRNs by using our general framework are discussed.

We investigate the memory effects in cyclically deformed amorphous solids through computer simulations. Applying oscillatory shear deformations in all orthogonal directions during encoding creates fault-tolerant memories that are agnostic to the reading direction. Our extensive system size analysis shows that memory encoding is faster in small systems and becomes exceedingly challenging as systems approach the thermodynamic limit. To capitalize on the quickness of memory encoding in small system sizes, it is important to demonstrate that memory can be encoded in nanoscale objects, where open surfaces play a crucial role. We achieve this by going from 3D bulk to pseudo-1D nanorods. Using tension-compression cycles on these nanorods, we show that memory encoding and reading are also possible in the presence of free surfaces.

We study an intriguing new type of self-assembled active colloidal polymer system in 3D. It is obtained from a suspension of Janus particles in an electric field that induces parallel dipoles in the particles as well as self-propulsion in the plane perpendicular to the field. At low volume fractions, in experiment, the particles self-assemble into 3D columns that are self-propelled in 2D. Explicit numerical simulations combining dipolar interactions and active self-propulsion find an activity dependent transition to a string phase by increasing dipole strength. We classify the collective dynamics of strings as a function of rotational and translational diffusion. Using an anisotropic version of the Rouse model of polymers with active driving, we analytically compute the strings’ collective dynamics and center of mass motion, which matches simulations and is consistent with experimental data. We also discover long range correlations of the fluctuations along the string contour that grow with the active persistence time, a purely active effect that disappears in the thermal limit.

Can spiking neural networks (SNNs) approximate the dynamics of recurrent neural networks? Arguments in classical mean-field theory based on laws of large numbers provide a positive answer when each neuron in the network has many “duplicates”, i.e., other neurons with almost perfectly correlated inputs. Using a disordered network model that guarantees the absence of duplicates, we show that duplicate-free SNNs can converge to recurrent neural networks, thanks to the concentration of measure phenomenon. This result reveals a general mechanism underlying the emergence of rate-based dynamics in large SNNs.

We discuss quantum network Bell nonlocality in a setting where the network structure is not fully known. More concretely, an honest user may trust their local network topology, but not the structure of the rest of the network, involving distant (and potentially dishonest) parties. We demonstrate that quantum network nonlocality can still be demonstrated in such a setting, hence exhibiting topological robustness. Specifically, we present quantum distributions obtained from a simple network that cannot be reproduced by classical models, even when the latter are based on more powerful networks. In particular, we show that in a large ring network, the knowledge of only a small part of the network structure (involving only two or three neighboring parties) is enough to guarantee nonlocality over the entire network. This shows that quantum network nonlocality can be extremely robust to changes in the network topology. Moreover, we demonstrate that applications of quantum nonlocality, such as the black-box certification of randomness and entanglement, are also possible in such a setting.

It was recently revealed by Cabello in a theoretical Letter [Phys. Rev. Lett. 127, 070401 (2021)] that nonlocality and contextuality, as two intuitively distinctive yet both critical quantum resources, can be surprisingly connected through Bell inequalities associated with state-independent contextuality sets. It provides a general unified method capable of converting contextuality into bipartite nonlocality. However, experimental tests of the inequalities are challenging and noise sensitive, and the requirements for the quantum states purity, dimensionality, and degree of entanglement have blocked the experimental implementation. We report a first experimental test of Cabello’s inequalities from state-independent contextuality sets, by leveraging two-photon high-dimensional orbital angular momentum entangled states. Distinguishing from the standard single-particle ways, our experiment spotlights that the state-independent contextuality sets can be tested in a bipartite scenario, by which the “compatibility” or “sharpness” loopholes can be effectively avoided. Our results provide a new perspective and demonstrate the principle that contextuality, a widely used quantum resource, can be used in different physical scenarios.