Integrated photonic systems provide a flexible platform where artificial lattices can be engineered in a reconfigurable fashion. Here, we show that one-dimensional photonic arrays with engineered losses allow the realization of topological excitations stemming from non-Hermiticity and bulk mode criticality. We show that a generalized modulation of the local photonic losses allows the creation of topological modes both in the presence of periodicity and even in the quasiperiodic regime. We demonstrate that a localization transition of all the bulk photonic modes can be engineered in the presence of a quasiperiodic loss modulation, and we further demonstrate that such a transition can be created in the presence of both resonance frequency modulation and loss modulation. We finally address the robustness of this phenomenology to the presence of next to the nearest neighbor couplings and disorder in the emergence of criticality and topological modes. Our results put forward a strategy to engineer topology and criticality solely from engineered losses in a photonic system, establishing a potential platform to study the impact of nonlinearities in topological and critical photonic matter.

We present results of the coefficient of thermal expansion for the frustrated quasi-two-dimensional molecular conductor $\theta \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_2\mathrm{RbZn}{\left(\mathrm{SCN}\right)}_4$ for temperatures $1.5\le T\le 290$ K. A pronounced first-order phase transition anomaly is observed at the combined charge-order/structural transition at 215 K. Furthermore, clear evidence is found for two separate glasslike transitions at $T_{\mathrm{g}}=90$–100 K and $T_{\mathrm{g}}^{†}=120$–130 K, similar to previous findings for $\theta \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_2\mathrm{CsZn}{\left(\mathrm{SCN}\right)}_4$ and $\theta \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_2\mathrm{CsCo}{\left(\mathrm{SCN}\right)}_4$ reported by Thomas et al. [Phys. Rev. B 105, L041114 (2022)], both of which lack the charge-order/structural transition. Our findings indicate that these glasslike transitions are common features for the $\theta \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_{2}M{M}^{\prime }{\left(\mathrm{SCN}\right)}_4$ family, with $M=(\mathrm{Rb}, \mathrm{Cs})$ and $M^{\prime }=(\mathrm{Co}, \mathrm{Zn})$, irrespective of the presence or absence of charge order. These results are consistent with our model calculations on the glasslike dynamics associated with the flexible ethylene end groups of the BEDT-TTF molecules for various $\theta \text{−}{\left(\mathrm{BEDT}\text{−}\mathrm{TTF}\right)}_{2}M{M}^{\prime }{\left(\mathrm{SCN}\right)}_4$ salts, predicting two different conformational glass transitions. Moreover, calculations of the hopping integrals show a substantial degree of dependence on the end groups' conformation, suggesting a significant coupling to the electronic degrees of freedom. Our findings support the possibility that the glassy freezing of the ethylene end groups could drive or enhance glassy charge dynamics.

We study various quantum quench processes induced by the Möbius/sine-square deformation of the Hamiltonian in two-dimensional conformal field theories starting from the thermofield double state in the two copies of the Hilbert space. These quantum quenches, some of which are directly related to the operator entanglement of the time-evolution operators, allow us to study scrambling and recovery of quantum information. In particular, under the sine-square deformed time evolution, we show from the time dependence of mutual information that the Bell pairs, initially shared by the subsystems of the two Hilbert spaces, may revive even after the mutual information for small subsystems is completely destroyed by quantum information scrambling dynamics. This mutual information is robust against the strong scrambling dynamics. As a consequence, the steady state has a nonlocal correlation shared not by any of two parties but by three parties. In the holographic dual description, a wormhole connecting the two Hilbert spaces may nonlinearly grow with time during the quantum quenches. We also propose effective pictures that describe the dynamics of mutual information during the time evolution by inhomogeneous Hamiltonians.

We investigate irradiated high-mobility two-dimensional electron systems (2DES) under low or moderated magnetic fields. These systems present microwave-induced magnetoresistance oscillations (MIRO) which, as we demonstrate, reveal the presence of coherent states of the quantum harmonic oscillator. We also show that the principle of minimum uncertainty of coherent states is at the heart of MIRO and zero-resistance states (ZRS). Accordingly, we are able to explain, based on coherent states, important experimental evidence of these photo-oscillations, such as their physical origin, their periodicity with the inverse of the magnetic field and their peculiar oscillations minima and maxima positions in regards of the magnetic field. Thus, remarkably enough, we come to the conclusion that 2DES, under low magnetic fields, become a system of quasiclassical states or coherent states and MIRO would be the smoking gun of the existence of these peculiar states in these systems.

The Ising model describes collective behaviors such as phase transitions and critical phenomena in various physical, biological, economical, and social systems. It is well known that spontaneous phase transition at finite temperature does not exist in the Ising model with short-range interactions in one dimension. Yet, little is known about whether this forbidden phase transition can be approached arbitrarily closely—at fixed finite temperature. Here I use symmetry analysis of the transfer matrix to reveal the existence of spontaneous ultranarrow phase crossover (UNPC) at finite temperature in one class of one-dimensional Ising models on decorated two-leg ladders, in which the crossover temperature $T_0$ is determined solely by on-rung interactions and decorations, while the crossover width $2\delta T$ is independently, exponentially reduced ($\delta T=0$ means a genuine phase transition) by on-leg interactions and decorations. These findings establish a simple ideal paradigm for realizing an infinite number of one-dimensional Ising systems with spontaneous UNPC at desirable $T_0$, which would be characterized in routine laboratory measurements as a genuine first-order phase transition with large latent heat thanks to the ultranarrow $\delta T$ (say less than one nanokelvin), paving a way to push the limit in our understanding of phase transitions and the dynamical actions of frustration arbitrarily close to the forbidden regime.

The proton-boron (p-${}^{11}\mathrm{B}$) reaction is regarded as the holy grail of advanced fusion fuels, since the primary reaction produces three $\alpha$ particles with few neutrons and induced radioactivities from second order reactions. Compared to the deuterium-tritium reaction a much higher reaction temperature is required. Moreover, bremsstrahlung energy losses due to the high nuclear charge of boron deem it seemingly apparent than a fusion reactor based on deuterium-tritium plasma in equilibrium is to say the least very difficult. It is becoming more appealing to collide intense laser beams or accelerated proton beams with a boron target to produce p-${}^{11}\mathrm{B}$ reactions. The fusion yield of p-${}^{11}\mathrm{B}$ reactions is closely related to proton beam parameters and boron target conditions such as density, temperature, and ingredients. Degeneracy will increase fusion yields by reducing the stopping power of injected protons. In this work, we suggest a scheme for beam-target p-${}^{11}\mathrm{B}$ fusions via injecting a MeV proton beam into a highly compressed quantum degenerated boron target. Such a boron target can be achieved via quasi-isentropic compression of solid boron by using precisely shaped laser pulses. Our results indicate that for densities ranging from ${10}^3$ to ${10}^4{\rho }_s$, where ${\rho }_s$ is the density of solid boron, contributions of bound and free electrons to the stopping of protons can be completely disregarded and dramatically reduced, respectively. The result is an increase in fusion yield by orders of magnitude. Furthermore, in order to achieve multiplication factor $F$ greater than one, with $F$ defined as the ratio of output fusion energy to the energy of injected protons, it is found there exists a minimum possible density of boron target, which is $1.8\times {10}^5{\rho }_s$ when the kinetic energy of injected protons is 880 keV.

Anderson localization has been widely studied in low-dimensional aperiodic electronic, photonic, and acoustic systems. However, the disorder effect in the plasmonic system, where retardation and long-range couplings interact in complex ways, remains an open question. In this work, we investigate the localization properties of one-dimensional quasiperiodic plasmonic chains using the coupled dipole method and linearized Green's function. Our models, which incorporate nearest-neighbor or long-range dipole interactions, reveal localization transitions, mobility edges, and intermediate phases. It is found that long-range dipole interactions and non-Hermiticity due to retardation both play crucial roles in Anderson localization, yielding the emergence of intermediate phases with varying widths. A link between non-Hermiticity and Anderson transition is established by the mean phase rigidity, revealing strong non-Hermiticity along the phase boundary. The plasmonic model involving long-range interplay and retarded effect presents richer localization phenomena than the electronic counterpart that usually includes only nearest-neighbor coupling, laying a foundation for experimental observations of Anderson localization on plasmonic platforms.

The Toffoli gate is the essential ingredient for reversible computing, an energy-efficient classical computational paradigm that evades the energy dissipation resulting from Landauer's principle. In this paper, we analyze different setups to realize a magnetic implementation of the Toffoli gate using three interacting classical spins, each one embodying one of the three bits needed for the Toffoli gate. In our scheme, different control-spin configurations produce an effective field capable of conditionally flipping the target spin. We study what the experimental requirements are for the realization of our scheme, focusing on the degree of local control, the ability to dynamically switch the spin-spin interactions, and the required single-spin anisotropies to make the classical spin stable, showing that these are compatible with current technology.

We prove that the motion of a single hole induces $SU\left(N\right)$ flavor singlets in the $U=\infty SU\left(N\right)$ (Fermi) Hubbard model on a Husimi-like tree graph. The result is generalized to certain $t\text{−}J$ models with singlet hopping terms typically neglected in the literature. This is an $SU\left(N\right)$ generalization of the “counter-Nagaoka theorem” introduced in [Phys. Rev. B 107, L140401 (2023)]. Our results suggest the existence of resonating flavor singlet (RFS)-like polarons in the $t\text{−}J$ models on a more realistic nonbipartite lattice. Such RFS polarons may be relevant for a novel strong-coupling mechanism of superconductivity or other exotic fractionalized phases of matter.

Fracton codes host unconventional topological states of matter and are promising for fault-tolerant quantum computation due to their large coding space and strong resilience against decoherence and noise. In this paper, we investigate the ground-state properties and phase transitions of two prototypical self-dual fracton spin models—the tetrahedral Ising model and the fractal Ising model—which correspond to error-correction procedures for the representative fracton codes of type I and type II, the checkerboard code and the Haah's code, respectively, in the error-free limit. They are endowed with exotic symmetry-breaking properties that contrast sharply with the spontaneous breaking of global symmetries and deconfinement transition of gauge theories. To show these unconventional behaviors, which are associated with subdimensional symmetries, we construct and analyze the order parameters, correlators, and symmetry generators for both models. Notably, the tetrahedral Ising model acquires an extended semilocal ordering moment, while the fractal Ising model fits into a polynomial ring representation and leads to a fractal order parameter. Numerical studies combined with analytical tools show that both models experience a strong first-order phase transition with an anomalous $L^{-(D-1)}$ scaling, despite the fractal symmetry of the latter. Our paper provides a unique understanding of subdimensional symmetry breaking and makes an important step for studying quantum-error-correction properties of the checkerboard and Haah's codes.

We introduce a gauge-invariant model of planar, square molecules coupled to a quantized spatially varying cavity electromagnetic vector potential $\widehat{\mathit{A}}\left(\mathit{r}\right)$. Specifically, we choose a temporally chiral cavity hosting a uniform magnetic field $\widehat{\mathit{B}}$, as this is the simplest instance in which a transverse spatially varying $\widehat{\mathit{A}}\left(\mathit{r}\right)$ is at play. We show that when the molecules are in the Van Vleck paramagnetic regime, an equilibrium quantum phase transition to a photon condensate state occurs.

We investigate the fate of the Kitaev spin liquid (KSL) under the influence of an external magnetic field $h$ in the [001] direction and upon tuning bond anisotropy of the Kitaev coupling $K_z$ keeping $K_x=K_y=K$. Guided by density matrix renormalization group, exact diagonalization, and with insights from parton mean-field theory, we uncover a field-induced gapless-to-gapless Lifshitz transition from the nodal KSL to an intermediate gapless phase. The intermediate phase sandwiched between $h_{c1}$ and $h_{c2}$, which persists for a wide range of anisotropy $K_z/K>0$, is composed of weakly coupled one-dimensional quantum critical chains. This intermediate phase is a dimensional crossover, which asymptotically leads to the one-dimensional quantum Ising criticality characterized by the $(1+1)\mathrm{D}$ conformal field theory as the field reaches the phase transition at $h_{c2}$. Beyond $h_{c2}$ the system enters a partially polarized phase describable as effectively decoupled bosonic chains in which spin waves propagate along the one-dimensional zigzag direction. Our findings provide a comprehensive phase diagram and offer insights into the unusual physics of dimensional reduction generated by a uniform magnetic field in an otherwise two-dimensional quantum spin liquid.

Self-oscillations are the result of an efficient mechanism generating periodic motion from a constant power source. In quantum devices, these oscillations may arise due to the interaction between single electron dynamics and mechanical motion. We show that, due to the complexity of this mechanism, these self-oscillations may irrupt, vanish, or exhibit a bistable behavior causing hysteresis cycles. We observe these hysteresis cycles and characterize the stability of different regimes in both single- and double-quantum-dot configurations. In particular cases, we find these oscillations stable for over 20 s, many orders of magnitude above electronic and mechanical characteristic timescales, revealing the robustness of the mechanism at play.

Van der Waals interactions are ubiquitous and they play an important role for the stability of materials. Current understanding of this type of coupling is based on linear response theory, while optical nonlinearities are rarely considered in this context. Many materials, however, exhibit strong optical nonlinear response, which prompts further evaluation of dispersive forces beyond linear response. Here we present a discrete coupled nonlinear dipole approach that takes into account linear and nonlinear properties of all dipolar nanoparticles in a given system. This method is based on a Hamiltonian for nonlinear dipoles, which we apply in different systems uncovering a complex interplay of distance, anisotropy, polarizabilities, and hyperpolarizabilities in the vdW energy. This investigation broadens our basic understanding of dispersive interactions, especially in the context of nonlinear materials.

We present a universal parameter-free quantum Monte Carlo (QMC) algorithm designed to simulate arbitrary spin-$1/2$ Hamiltonians. To ensure the convergence of the Markov chain to equilibrium for every conceivable case, we devise a clear and simple automated protocol that produces QMC updates that are provably ergodic and satisfy detailed balance. We demonstrate the applicability and versatility of our method by considering several illustrative examples, including the simulation of the XY model on a triangular lattice, the toric code, and random $k$-local Hamiltonians.

The role of quantum fluctuations in modifying the critical behavior of nonequilibrium phase transitions is a fundamental but unsolved question. In this study, we examine the absorbing state phase transition of a 1D chain of qubits undergoing a contact process that involves both coherent and classical dynamics. We adopt a discrete-time quantum model with states that can be described in the stabilizer formalism, and therefore allows for an efficient simulation of large system sizes. The extracted critical exponents indicate that the absorbing state phase transition of this Clifford circuit model belongs to the directed percolation universality class. This suggests that the inclusion of quantum fluctuations does not necessarily alter the critical behavior of nonequilibrium phase transitions of purely classical systems. Finally, we extend our analysis to a non-Clifford circuit model, where a tentative scaling analysis in small systems reveals critical exponents that are also consistent with the directed percolation universality class.