In this work we address quantum vacuum amplification effects in time-varying media with an arbitrary time-modulation profile. To this end, we propose a theoretical formalism based on the concept of conjugated harmonic oscillators, evaluating the impact on the transition time in temporal boundaries, shedding light into the practical requirements to observe quantum effects at them. In addition, we find nontrivial effects in pulsed modulations, where the swiftest and strongest modulation does not lead to the highest photon production. Thus, our results provide key insights for the design of temporal modulation sequences to enhance quantum phenomena.

The mode-coupling theory (MCT) of the glass transition ranks among the most successful first-principles kinetic theories to describe glassy dynamics. However, MCT does not fully account for crucial aspects of the dynamics near the glass transition. To facilitate improving the theory, we critically test the approximations inherent in MCT for a supercooled mixture using Brownian dynamics simulations. Although each MCT approximation significantly impacts the predicted dynamics, our findings show that long-time cancellations of errors occur due to static and dynamic approximations of four-point correlation functions, with the validity of these approximations remaining relatively constant across different temperatures. Notably, the MCT form of the memory functional maintains remarkably high accuracy even in the supercooled regime when evaluated with the intermediate scattering function from simulations. The primary discrepancies between theoretical predictions and experimental results arise from the self-consistent nature of the MCT equations, which amplify minor errors in the memory kernel. This suggests that minor corrections to the memory functional could substantially enhance the theory's predictive accuracy.

In recent years, quantum computing has evolved as an exciting frontier, with the development of numerous algorithms dedicated to constructing quantum circuits that adeptly represent quantum many-body states. However, this domain remains in its early stages and requires further refinement to better understand the effective construction of highly entangled quantum states within quantum circuits. Here, we demonstrate that quantum many-body states can be universally represented using a quantum circuit comprising multiqubit gates. Furthermore, we evaluate the efficiency of a quantum circuit constructed with two-qubit gates in quench dynamics for the transverse-field Ising model. In this specific model, despite the initial state being classical without entanglement, it undergoes long-time evolution, eventually leading to a highly entangled quantum state. Our results reveal that a diamond-shaped quantum circuit, designed to approximate the multiqubit gate-based quantum circuit, remarkably excels in accurately representing the long-time dynamics of the system. Moreover, the diamond-shaped circuit follows the volume law behavior in entanglement entropy, offering a significant advantage over alternative quantum circuit constructions employing two-qubit gates.

Laser ablation is performed on an oxidized, roughly 35-year-old ${}^{232}\mathrm{Th}$ foil. The produced anionic and cationic molecules are investigated utilizing precision mass measurements by a multireflection time-of-flight mass spectrometer. Molecules with up to three thorium atoms are identified. This includes oxides ${\mathrm{Th}}_n{\mathrm{O}}_x^{+}$ containing up to $2n-1$ oxygen atoms and further species incorporating carbon or nitrogen. In addition, signals of ${\mathrm{U}}^{+}, {\mathrm{UO}}^{+}$, and the compound species ${\mathrm{ThUO}}_2^{+}$ are found. Photoexcitation reveals selected molecules' dissociation patterns. The experimental findings are compared to density functional theory calculations.

Channel simulation using coherence, which refers to realizing a target channel with coherent states and free operations, is a fundamental problem in the quantum resource theory of coherence. The limitations of the accuracy of deterministic channel simulation motivate us to consider the more general probabilistic framework. In this paper, we develop the framework for probabilistic channel simulation using coherence with free operations. When the chosen set of free operations is the maximally incoherent operations, we provide an efficiently computable semidefinite program (SDP) to calculate the maximal success probability and derive the analytic expression of success probability for some special cases. When the chosen set of free operations is the dephasing-covariant incoherent operations (DIO), we show that if the target channel is not a resource nonactivating channel then one cannot simulate it exactly both deterministically and probabilistically. The SDP for maximal success probability of simulating a channel by DIO is also given correspondingly.

The critical Kauffman model with connectivity one is the simplest class of critical Boolean networks. Nevertheless, it exhibits intricate behavior at the boundary of order and chaos. We show that the model is equivalent to a deceptively simple algebraic system of polynomials which count the number and length of cycles. The polynomial for multiple loops is the product of the polynomials for individual loops. Using this perspective, we prove that the number of cycles scales as $2^m$, where $m$ is the number of nodes in loops—as fast as possible and faster than previously believed.

Light-matter interfaces have now entered a new stage marked by the ability to engineer quantum correlated states under driven-dissipative conditions. To propel this new generation of experiments, we are confronted with the need to model nonunitary many-body dynamics in strongly coupled regimes by transcending traditional approaches in quantum optics. In this work, we contribute to this program by adapting a functional-integral technique, conventionally employed in high-energy physics, in order to obtain nonequilibrium dynamics for interacting light-matter systems. Our approach is grounded in constructing “two-particle irreducible” (2PI) effective actions, which provide a nonperturbative and conserving framework for describing quantum evolution at a polynomial cost in time. We apply our method to complement the analysis of spin-glass formation in the context of frustrated multimode cavity quantum electrodynamics, initiated in our accompanying work [Hosseinabadi et al., Phys. Rev. Res. 6, 043313 (2024)]. Finally, we outline the capability of the technique to describe other near-term platforms in many-body quantum optics, and its potential to make predictions for this new class of experiments.

By solving the quench dynamics of a frustrated many-body spin-boson problem, we investigate the role of spin size on the dynamical formation of spin-glass order. In particular, we observe that quantum and classical spin glasses exhibit markedly different evolution. The former displays a quick relaxation of magnetization together with an exponential dependence of the spin-glass order parameter on spin size, while the latter has long-lasting prethermal magnetization and a spin-glass order parameter independent of spin size. The quantum-to-classical crossover is sharp and occurs for relatively small spins, highlighting the fragility of the quantum regime. Furthermore, we show that spin-glass order is resonantly enhanced when the frequency of the bosonic mediators of the interactions approaches the value of the transverse field. Our predictions are directly applicable to the nonequilibrium dynamics of all spin-glass systems with SU(2) spins, such as the quantum Sherrington-Kirkpatrick model, and they can be examined in recently developed multimode cavity QED experiments.

Neuronal dendrites form densely branched tree architectures through which mitochondria must be distributed to supply the cell's energetic needs. Dendritic mitochondria circulate across the tree, undergoing fusion and fission to form clusters of varying sizes. We present a mathematical model for the distribution of such actively driven interacting particles in a branched geometry, showing that the density and localization of particles is highly sensitive to the fusion/fission balance and to the tree architecture. Our model demonstrates that “balanced” trees (wherein cross-sectional area is conserved across junctions and thicker branches support more bushy subtrees) enable symmetric yet distally enriched particle distributions and promote dispersion into smaller clusters. These results highlight the importance of tree morphology and radius-dependent fusion in governing the distribution of neuronal mitochondria.

We provide an insight into the origin of the phenomena reported 40 years ago by Kerker et al. [J. Opt. Soc. Am. 73, 765 (1983)]. We show that the impedance and refractive index matching conditions, discussed in Secs. II and IV of the seminal paper, are intertwined and both lead to the conservation of a Casimir invariant. We derive our results starting from the theory of representations of the Poincaré group, as it is a theory on which one of the most elemental descriptions of electromagnetic waves is based. We show that fundamental features of electromagnetic waves in continuous material environments can be derived by applying the symmetry-breaking principle. In particular, we identify the Casimir invariants of the $P_{3,1}$ subgroup as the magnitudes that describe the nature of monochromatic electromagnetic waves propagating in matter. Finally, we show that the emergence of the Kerker phenomena is associated with the conservation of such Casimir invariants in piecewise homogeneous media.

In this work, we investigate the effect of particle shape, ranging from spherical to highly concave, on steady flows in a rotating drum, a system that facilitates a continuous transition from a jamming state at greater depths to an unjamming state at shallower regions. We develop an analytical model to elucidate granular behavior within the rotating drum: (i) First, by decomposing the shear stress, we reconcile the discrepancy between simulation data and theoretical predictions, establishing a relationship with the angle of repose. (ii) Second, we extend the generalized Bagnold scaling, coupled with a nonlocal fluidity relation based on packing fraction, providing a framework for a correlation between shear stress, shear rate, and packing fraction. Additionally, we introduce a characteristic length to quantify the influence of particle shape and drum speed. This analytical model offers explicit functional forms for physical quantity profiles, which are validated experimentally in a thin rotating drum and numerically in a two-dimensional rotating drum. Our results demonstrate that this model accurately describes the change in velocity from the bottom of the drum to the free surface. Moreover, for different shapes of particle and drum speeds, the characteristic length captures the interplay between shear stress, shear rate, and the variation of packing fraction.

In this computational study, we explore a viable route to access the Kitaev-quantum spin liquid (QSL) state in a recently synthesized monolayer of a so-called spin-orbit assisted Mott insulator ${\mathrm{OsCl}}_3$. In addition to other magnetic ground states in different regions, a substantial region of small $J_{\text{H}}$/$U$ in our Hubbard $U$–Hund's $J_{\text{H}}$ quantum phase diagram, obtained by combining second-order perturbation and pseudo-fermion functional renormalization group calculations, hosts Kitaev-QSL phase. Only the first neighbor Kitaev interaction of a smaller magnitude, nearly independent of the choice of $U$, is obtained in this region. Experimental tuning of the single parameter $J_{\text{H}}$ to access the QSL state can purportedly be achieved with epitaxial strain in advanced crystal growth techniques. Furthermore, negligibly small farther neighbor interactions appear as a distinct feature of monolayer ${\mathrm{OsCl}}_3$, suggesting this material to be a better candidate for the exploration of the possible Kitaev-QSL state than previously proposed materials.

We present a combined experimental and theoretical study on the quasi-one-dimensional organic conductor (${\mathrm{TMTTF})}_2{\mathrm{PF}}_6$, and elucidate the variation of its physical properties under pressure. We fully resolve the crystal structure by single crystal x-ray diffraction measurements using a diamond anvil cell up to 8 GPa, and based on the structural data, we perform first-principles density-functional theory calculations and derive the ab initio extended Hubbard-type Hamiltonians. Furthermore, we compare the behavior of the resistivity measured up to 3 GPa using a BeCu clamp-type cell and the ground state properties of the obtained model numerically calculated by the many-variable variational Monte Carlo method. Our main findings are as follows: (i) The crystal was rapidly compressed up to about 3 GPa where the volume drops to 80% and gradually varies down to 70% at 8 GPa. The transfer integrals increase following such behavior whereas the screened Coulomb interactions decrease, resulting in a drastic reduction of correlation effect. (ii) The degree of dimerization in the intrachain transfer integrals, as the result of the decrease in structural dimerization together with the change in the intermolecular configuration, almost disappears above 4 GPa; the interchain transfer integrals also show characteristic variations under pressure. (iii) The results of identifying the characteristic temperatures in the resistivity and the charge and spin orderings in the calculations show an overall agreement: The charge ordering sensitively becomes unstable above 1 GPa, while the spin ordering survives up to higher pressures. These results shed light on the similarities and differences between applying external pressure and substituting the chemical species (chemical pressure).

Levitated nanoparticles are a promising platform for sensing applications and for macroscopic quantum experiments. While the nanoparticles' motional temperatures can be reduced to near absolute zero, their uncontrolled internal degrees of freedom remain much hotter, inevitably leading to the emission of heat radiation. The decoherence and motional heating caused by this thermal emission process is still poorly understood beyond the case of the center-of-mass motion of point particles. Here, we present the master equation describing the impact of heat radiation on the motional quantum state of arbitrarily sized and shaped dielectric rigid rotors. It predicts the localization of spatio-orientational superpositions only based on the bulk material properties and the particle geometry. A counterintuitive and experimentally relevant implication of the presented theory is that orientational superpositions of optically isotropic bodies are not protected by their symmetry, even in the small-particle limit.

Physical unclonable functions (PUFs) leverage inherent, nonclonable physical randomness to generate unique input-output pairs, serving as secure fingerprints for cryptographic protocols like authentication. Quantum PUFs (QPUFs) extend this concept by using quantum states as input-output pairs, offering advantages over classical PUFs, such as challenge reusability via public channels and eliminating the need for trusted parties due to the no-cloning theorem. Recent work introduced a generalized mathematical framework for QPUFs. It was shown that random unitary QPUFs cannot achieve existential unforgeability against quantum polynomial time (QPT) adversaries. Security was possible only with additional uniform randomness. To avoid the cost of external randomness, we propose a novel measurement-based scheme. Here, the randomness naturally arises from quantum measurements. Additionally, we introduce a second model where the QPUF functions as a nonunitary quantum channel, which guarantees existential unforgeability. These are the first models in the literature to demonstrate a high level of provable security. Finally, we show that the quantum phase estimation (QPE) protocol, applied to a Haar random unitary, serves as an approximate implementation of the second type of QPUF by approximating a von Neumann measurement on the unitary's eigenbasis.

A causal relation between quantum agents, say Alice and Bob, is necessarily mediated by an interaction. Modeling the latter as a reversible quantum channel, an intervention of Alice can have causal influence on Bob's system, modifying correlations between Alice and Bob's systems. Causal influence between quantum systems necessarily allows for signaling. Here we prove a mismatch between causal influence and signaling via direct computation of the two quantities for the $\mathrm{Cnot}$ gate. Finally we show a continuity theorem for causal effects of unitary channels: a channel has small causal influence if it allows for small signaling.

We investigate analytically the performance of many-body energy functionals, derived by Klein, Luttinger, and Ward, at different levels of diagrammatic approximations, ranging from second Born, to GW, to the so-called T matrix, for the calculation of total energies and potential energy surfaces. We benchmark our theoretical results on the extended two-site Hubbard model, which is analytically solvable and for which several exact properties can be calculated. Despite its simplicity, this model displays the physics of strongly correlated electrons: it is prototypical of the ${\mathrm{H}}_2$ dissociation, a notoriously difficult problem to solve accurately for the majority of mean-field-based approaches. We show that both functionals exhibit good to excellent variational properties, particularly in the case of the Luttinger-Ward one, which is in close agreement with fully self-consistent calculations, and we elucidate the relation between the accuracy of the results and the different input one-body Green's functions. Provided that these are wisely chosen, we show how the Luttinger-Ward functional can be used as a computationally inexpensive alternative to fully self-consistent many-body calculations, without sacrificing the precision of the results obtained. Furthermore, in virtue of this accuracy, we argue that this functional can also be used to rank different many-body approximations at different regimes of electronic correlation, once again bypassing the need for self-consistency.

We revisit the discussion of the quantum resources required to perform optimal unambiguous discrimination between two nonorthogonal quantum states when the protocol is assisted by an auxiliary system (ancilla). Initially, the formulation of the problem led to the assumption that entanglement between the main system and the ancilla was the key resource for the task. However, it was later shown that entanglement is not necessary at all, while quantum dissonance may or may not be required, depending on the relationship between the overlap and the a priori probabilities of the inputs [Zhang, Sci. Rep. 3, 2134 (2013)]. Here, we show that, regardless of this relationship, coherence and purity are required resources for the task and thus more fundamental than dissonance. Coherence is analyzed based on its generalized resource theory, which allowed us to find the scenario that generates the maximal cryptographic randomness gain in the protocol. Purity, on the other hand, is shown to be greater than coherence when both measures are defined via the same distance, including the extreme cases of orthogonal and parallel states, where the latter is zero. Therefore, we conclude that purity is the most fundamental resource for assisted optimal state discrimination.