The Landau-Brazovskii model provides a theoretical framework for describing various phases arising from competing short- and long-range interactions in many physical systems. In this work, we investigate phase transitions among various ordered phases within the three-dimensional Landau-Brazovskii model. We construct the phase diagram of this model, which encompasses eight distinct phases, and systematically compute the transition pathways connecting various metastable and stable states using the Landau-Brazovskii saddle dynamics. Along each transition pathway, the critical nucleus is identified with some detailed analyses of its shape, energy barrier, and Hessian eigenvalues. Furthermore, we explore how the transition state is influenced by model parameters, revealing systematic trends in critical nucleus sizes and energy barrier heights. Our results provide a comprehensive characterization of the nucleation mechanisms within the Landau-Brazovskii model and offer valuable insights into the structural transformations of modulated-phase systems.

Motivated by recent proposals for quantum proof of work protocols, we investigate approaches for simulating linear optical interferometers using digital quantum circuits. We focus on a second quantization approach, where the quantum computer's registers represent optical modes. We can then use standard quantum optical techniques to decompose the unitary matrix describing an interferometer into an array of $2\times 2$ unitaries, which are subsequently synthesized into quantum circuits and stitched together to complete the circuit. For an $m$-mode interferometer with $n$ identical photons, this method requires approximately $\mathcal{O}(mlog(n\left)\right)$ qubits and a circuit depth of $\mathcal{O}\left(m{n}^4{log}_2\left(n\right)\text{polylog}(n^4/\epsilon )\right)$. We present a software package aquinas (a quantum interferometer assembler) that uses this approach to generate such quantum circuits. For reference, an arbitrary five-mode interferometer with two identical photons is compiled to a ten-qubit quantum circuit with a depth of 1972.

The optical resonances supported by nanostructures offer the possibility to enhance the interaction between matter and quantum states of light. On the other hand, due to abrupt changes in the optical response the quantum states of light can be significantly affected by the interaction. In this work, we provide a framework to study the scattering of quantum states of light (with information encoded in their helicity) by a nanostructure. We analyze the purity of the scattered output quantum state and find that the purity of the incident state can be lost when it interacts with the optical resonances of the nanostructure. To explain the loss of quantum purity, we develop a physical picture based on time delays and frequency shifts between the output two-photon modes. The framework and analysis proposed in this work establish a tool to address the interaction between quantum light and nanoenvironments.

Chromosomes are complex biopolymers folded into dynamic loops via a loop-extrusion process and may experience various mechanical forces in vivo. We develop a force-dependent model of chromatin loop extrusion and investigate its mechanical consequences on chromosome organization using simulations and analytical theory. We show that loop extrusion alters the force-extension behavior of DNA in a nonmonotonic manner: Extrusion stiffens the chain at low forces but softens it at intermediate and high forces. Our model predicts hysteresis in pulling-recoiling cycles and out-of-equilibrium responses, qualitatively consistent with recent single-chromosome stretching experiments. We further find that loop extrusion provides mechanical robustness to chromatin by promoting compaction while enabling rapid structural recovery after stress. These results establish loop extrusion as a key regulator of chromatin mechanics.

Quantum computing and machine learning are state-of-the-art technologies that have been investigated intensively in both academia and industry. The hybrid technology of these two ingredients is expected to be a powerful tool to solve complex problems in many branches of science and engineering such as combinatorial optimization problems and accelerate the creation of next-generation technologies. In this work, we develop an algorithm to solve a black-box optimization problem by improving Factorization Machine Annealing (FMA) such that the training of a machine learning model called factorization machine is performed not by a full dataset but by a subdataset that is sampled from a full dataset: Subsampling Factorization Machine Annealing (SFMA). According to such a probabilistic training process, the performance of FMA on exploring a solution space gets enhanced. As a result, SFMA exhibits balanced performance of exploration and exploitation, which we call exploitation-exploration functionality. We conduct numerical benchmarking tests to compare the performance of SFMA with that of FMA. Consequently, SFMA certainly exhibits the exploration-exploitation functionality and outperforms FMA in speed and accuracy. In addition, the performance of SFMA can be further improved by sequentially using two subsampling datasets with different sizes such that the size of the latter dataset is substantially smaller than the former. Such a substantial reduction not only enhances the exploration performance of SFMA but also enables us to run it with correspondingly low computational cost even for a large-scale problem. These results indicate the effectiveness of SFMA in a certain class of black-box optimization problems of significant size: the potential scalability of SFMA in solving large-scale problems with correspondingly low computational cost. The exploitation-exploration functionality of SFMA is expected to pave the way for solving various complex combinatorial optimization problems in the real world and designing next-generation technologies that become the basic building blocks for industrial advancements.

This paper presents an efficient method for detecting entanglement in high-dimensional two-qudit states by mapping the Hilbert space onto the space of two qubits. This transformation enables the use of well-established two-qubit entanglement witnesses. The proposed approach is not restricted to any specific class of states, successfully identifies a vast majority of pure entangled states, and requires a number of measurements that does not increase with the dimensionality of the qudits. The method demonstrates solid sensitivity when applied to two notable classes of states—incomplete-permutation-symmetric states and random pure states mixed with white noise—and is shown to be feasible with current experimental techniques.

We consider a Bose-Einstein condensate (BEC) loaded into a one-dimensional optical cavity under the combined action of an external potential and atom-cavity coupling with mutually incommensurate periods. Such configuration enables the localization of matter waves even in the absence of two-body interactions. We study families of localized modes within the mean-field approximation for red and blue detunings from atomic and cavity resonances in relatively shallow quasiperiodic lattices, beyond the validity of the tight-binding approximation. The parameter regimes supporting localization of atomic wave packets are identified. The system exhibits two types of bistability manifested as distinct photon numbers under otherwise identical conditions. One type arises from the coexistence of multiple families of localized modes, typical of conservative nonlinear systems, while the other stems from the multivalued dependence of the families on system parameters, characteristic of systems exhibiting hysteresis. BEC in a cavity may also display pseudodegeneracy, understood as the existence of two distinct atomic-density distributions corresponding to the same atomic and photon numbers (although different chemical potentials). The stability of the localized modes is analyzed. It is shown that, owing to the strong impact of long-range interactions on stability, a two-localized-mode configuration can operate as an xor logic gate.

Synapses in the nervous system show considerable volatility, raising the question of how the brain maintains functional stability despite continuous synaptic motility. Previous studies have suggested that functionality may be maintained by an ongoing process of activity-dependent plasticity. Here, we address this question in the context of rhythmogenesis. Specifically, we investigated the hypothesis that rhythmic activity in the brain can develop and be stabilized via activity-dependent plasticity in the form of spike-timing-dependent plasticity (STDP), thus extending our previous work that demonstrated rhythmogenesis in a toy model of two effective neurons. We examined STDP dynamics in large recurrent networks in two stages. We first derived the effective dynamics of the order parameters of the synaptic connectivity. Then, a perturbative approach was applied to investigate stability. We show that for a wide range of parameters, STDP can induce rhythmogenesis. Moreover, STDP can suppress synaptic fluctuations that disrupt functionality. Interestingly, STDP can channel fluctuations in the synaptic weights into a manifold in which the network activity is not affected, thus maintaining functionality while allowing a subspace in which synaptic weights can be widely distributed.

The ability to efficiently simulate a variety of interacting quantum systems on a single device is an overarching goal for digital and analog quantum simulators. In circuit quantum electrodynamical systems, strongly nonlinear superconducting oscillators are typically realized using transmon qubits, featuring a wide range of tunable couplings that are mainly achieved via flux-dependent inductive elements. Such controllability is highly desirable both for digital quantum information processing and for analog quantum simulations of various physical phenomena, such as arbitrary spin-spin interactions. Furthermore, broad tunability facilitates the study of driven-dissipative oscillator dynamics in previously unexplored parameter regimes. In this work, we demonstrate the ability to selectively activate different dynamical regimes between two strongly nonlinear oscillators using parametric modulation. In particular, our scheme enables access to regimes that are dominated by photon hopping, two-mode squeezing, or cross-Kerr interactions. Finally, we observe level repulsion and attraction between Kerr-nonlinear oscillators in regimes where the nonlinearities exceed the coupling strengths and decay rates of the system. Our results could be used for realizing purely analog quantum simulators to study arbitrary spin systems as well as for exploring strongly nonlinear oscillator dynamics in previously unexplored interaction regimes.

Geometrical frustration in quantum magnets provides a fertile setting for unconventional phases of matter, including quantum spin liquids (QSLs). The trellis lattice, with its complex site arrangements and edge-sharing triangular motifs, presents a promising platform for such physics. In this work, we undertake a comprehensive classification of all fully symmetric QSLs on the trellis lattice using the projective symmetry group approach within the Abrikosov-fermion representation. We find 7 U(1) and 25 ${\mathbb{Z}}_2$ short-ranged Ansätze and analyze the phase diagram in the mean-field parameter space, uncovering both gapped and Dirac QSLs as well as a semi-Dirac spin liquid that emerges at the level of projective symmetry group classification and mean-field band structure, in which the spinon dispersion is linear along one momentum direction but quadratic along the orthogonal one. We demonstrate that such dispersions can occur only at high-symmetry points in the Brillouin zone with $C_{2v}$ little groups and analyze their characteristic correlation signatures. Moreover, by optimizing over all symmetry-allowed mean-field states, we map out a phase diagram—featuring six distinct phases—of the nearest-neighbor Heisenberg Hamiltonian on the trellis lattice. Among these, we find four quasi-one-dimensional QSL phases, one dimer phase, and one Dirac QSL phase. Going beyond mean field, we also assess equal-time and dynamical spin structure factors of these phases using density-matrix renormalization group and Keldysh pseudofermion functional renormalization group calculations and compare qualitative momentum-space features of these spectra with those obtained at the mean-field level. Finally, we identify four cuprate and vanadate compounds as promising experimental realizations and provide spectroscopic predictions, based on first-principles Hamiltonians, as a guide for future neutron-scattering studies on these materials.

We study an unconventional phase transition in ferroelectrics where the polarization field is constrained to be divergence-free, allowing only looplike configurations. This local constraint fundamentally alters the critical behavior, driving the system beyond the Landau-Ginzburg-Wilson paradigm. A renormalization group analysis shows that the polarization acquires an unusually large anomalous dimension, $\eta \approx 0.239$ in three dimensions, far exceeding the typical values in $O\left(3\right)$-invariant systems. We attribute this effect to a naturally induced gauge symmetry originating from the zero-divergence constraint. Such constraint-induced gauge-field behavior is reminiscent of fractionalized phases, revealing a fundamental connection between constrained ferroelectrics and emergent gauge phenomena in correlated matter.

Future global quantum communication networks, or quantum internet, will realize high-rate secure communication and entanglement distribution for large-scale users over long distances. Continuous variable (CV) quantum key distribution (QKD) provides a powerful setting for secure quantum communications, thanks to the use of room-temperature off-the-shelf optical devices and the potential to reach high rates. However, the achievable performance of CV-QKD protocols is fundamentally limited by the fact that they appear to be fragile to both loss and noise. In this study, we provide a general framework for analyzing the composable finite-size security of CV-QKD with Gaussian-modulated coherent-state (GMCS) protocol under various levels of trust for the loss and noise experienced by the users of the protocol. Our work is comprehensive of several practical scenarios, encompassing both active and passive eavesdropping configurations, with both wired (i.e., fiber-based) and wireless (i.e., free-space and satellite-based) quantum communication channels. Our numerical results evaluate the robustness of the GMCS protocol under varying levels of trust and demonstrate that it is difficult for a practical protocol to remain robust against untrusted loss at the transmitter. In the wireless case, we analyze a scenario with a sun-synchronous satellite, showing that its key distribution rate, even with the worst level of trust, can outperform a ground chain of ideal quantum repeaters. Our results indicate that—when it comes to engineering and optimizing quantum-safe networks—it is essential to mitigate the shortcomings caused by critical trade-offs between rate performance, trust level, system noise, and communication distance.

Multimode N00N states stand out as an excellent platform to explore higher-order quantum interference phenomena, with benefits in quantum-enhanced estimation of multiple parameters beyond classical limits. Here, we investigate higher-order polarization properties, geometric phase features, and associated wave-particle duality structures in double-slit vector-light interference involving a multimode N00N state. We particularly show that the interferometric polarization modulation and the accompanied geometric phase accumulation are $N$ times faster for the multimode N00N state than for one-photon or classical light. We also formulate $N\mathrm{th}$-order extensions of the three wave-particle duality relations established for a single vector-light photon: the two via distinguishabilities and visibilities [A. Norrman et al., Phys. Rev. Lett. 119, 040401 (2017)], and the one via the geometric phase and which-path information ratio [E. Pillinen et al., Phys. Rev. A 111, 063709 (2025)]. Our work contributes to the broader fundamental understanding of how vectorial quantum light acts in higher-order interference, with possible opportunities in precision metrology outside scalar-field regimes.

We have demonstrated the coherent storage and retrieval of single-photon-level light using the atomic frequency comb protocol in a room temperature rubidium vapor. Velocity-selective optical pumping is used to prepare the comb within the $F=2$ hyperfine ground state of rubidium, with the spacing between peaks coinciding with half the $F=2-F=3$ hyperfine splitting of the $5{}^2\mathrm{P}_{3/2}$ excited state. Weak coherent states of average photon number ${\mu }_{\mathrm{in}}=0.083\left(5\right)$ are stored with preprogrammed recall time of $7.5\mathrm{ns}$ with an efficiency of ${\eta }_{\text{AFC}}=6.59\left(5\right)\%$, while two temporally distinct modes have been stored and recalled with ${\eta }_{\text{AFC}}=2.6\left(1\right)\%$, allowing for time-bin qubit storage. Finally, the storage efficiency is observed to be independent of the input pulse polarization, satisfying a necessary condition for polarization qubit storage.

We systematically characterize the focusing behavior of laser-driven proton beams from hemispherical targets of various diameters using mesh radiography. The proton focal location is inferred to be near the geometrical center for the smallest tested hemisphere ($\mathrm{\Psi }=D_{\text{hemi}}/D_{\text{Laser}}=6.1$). However, larger hemispheres ($\mathrm{\Psi }=14.6$) degrade the focusing behavior and behave more like flat foils with focal location significantly inside the hemisphere. We also infer a tight virtual focus of $9\pm 3\mu \mathrm{m}$ through a mesh transition analysis.

We explore the relation between quantum geometry in non-Hermitian systems and physically measurable phenomena. We highlight various situations in which the behavior of a non-Hermitian system is best understood in terms of quantum geometry, namely, the notion of adiabatic potentials in non-Hermitian systems and the localization of Wannier states in periodic non-Hermitian systems. Further, we show that the non-Hermitian quantum metric appears in the response of the system upon time-periodic modulation, which one can use to experimentally measure the non-Hermitian quantum metric. We validate our results by providing numerical simulations of concrete exemplary systems.

In a series of axisymmetric core-collapse supernova simulations extending up to $\sim 2\mathrm{s}$, we identify a regime of precollapse central rotation rates ($\sim 1\mathrm{Hz}$) that greatly enhances the emission of gravitational waves (GWs) during extended periods of time after bounce. The enhancement is a consequence of the resonance between the frequency of the fundamental quadrupolar ${}^{2}f$ mode of oscillation of the protoneutron star and the frequency of the epicyclic oscillations at the boundary of the inner core. We observe periods of about several hundred milliseconds each where the resonance is active. The GW emission enhancement produces a correlated resonant modulation of the associated neutrino signal at the same frequencies. With GW frequencies of $\mathcal{O}\left(1\mathrm{kHz}\right)$ and strain amplitudes within the sensitivity curves of current and next-generation interferometers at distances of $\mathcal{O}\left(1\mathrm{Mpc}\right)$, this resonant-amplification mechanism may represent a potential game changer for unveiling the supernova explosion mechanism through multimessenger astronomy.

We present the simulation of the quench dynamics of the ${\mathbb{Z}}_3$ Schwinger model, which describes an approximation of one-dimensional quantum electrodynamics, on a digital noisy Rydberg atom platform, aiming at the observation of multiple dynamical quantum phase transitions. In order to reach long-time dynamics, we exploit an encoding dictated by the symmetries, combined with a circuit compression procedure. We focus on a quench that evolves the Dirac vacuum by means of a Hamiltonian depending on a negative mass parameter. This leads to resonant Rabi oscillations between the Dirac vacuum and mesonic states. The population concentration exhibits oscillations with negligible fluctuations of detuned states also with the inclusion of combined noise sources, from which we can clearly detect multiple dynamical phase transitions.