Light in the mode of a Fabry-Pérot cavity heats the mirror surfaces via optical absorption, causing thermoelastic deformation of the mirror substrates, which in turn dictates the shape of the mode. We develop an analytical model which predicts that this effect limits the maximum focal intensity of the mode. Using two near-concentric Fabry-Pérot cavities—one with 4.5-fold-higher mirror absorption than the other—we measure the thermoelastic properties of the cavity mirrors and demonstrate that it is possible to achieve at least $70\%$ of this predicted limit (in the high-absorption cavity) and that the predicted limit is $2.9\mathrm{TW}/{\mathrm{cm}}^2$ (in the low-absorption cavity).

Soliton rain is a typical multipulse dissipative structure in passively mode-locked fiber lasers, where the drift direction of drifting solitons (DSs) reflects the balance among gain, nonlinearity, dispersion, loss, and intracavity filtering. Here, we show that the drift symmetry of soliton rain can be tuned by changing the length of the polarization-maintaining fiber (PMF) in a passively mode-locked erbium-doped fiber laser. The PMF, together with the intracavity polarization elements, forms an equivalent Lyot filter whose wavelength-dependent transmission modifies the spectral-energy redistribution around the condensed soliton phase (CSP). Experiments and simulations indicate that gain accumulation enables soliton-rain formation, while the birefringence-induced filtering condition biases the DS drift direction and supports switching between unidirectional and bidirectional soliton rain. Correlation analysis, mutual information, cross-correlation, and three-dimensional phase-space reconstruction further reveal the internal interaction dynamics between the CSP and DSs. These results identify PMF-induced birefringence as an effective control knob for drift-symmetry selection, rather than the sole origin of soliton-rain formation.

Exceptional points (EPs) represent non-Hermitian degeneracies where eigenvalues and eigenvectors coalesce, giving rise to enhanced sensitivity and critically damped dynamics. We demonstrate that when an EP coincides with a dissipative phase transition in an extended open Dicke model of two cavities coupled to a collective spin, the critical fluctuations are strongly amplified and governed by modified critical exponents. Numerical results reveal enhanced critical scaling in both the normal and superradiant phases, in agreement with an analytical theory based on the Jordan-block structure of the linearized dynamical matrix at the EP. Our results establish EPs as a mechanism to engineer critical scaling in open quantum systems, with potential applications to critical quantum sensing.

We propose an ultrafast free-electron quantum interferometry, facilitating the detection of local electromagnetic fields and plasmonic polaritons using an isolated “two-level” electron. The two-level electron is constructed in a synthetic energy space through laser modulation in the Bragg regime. This construction allows the π/2-pulse and π-pulse Rabi oscillation of the electron to serve as “beam splitters” and “mirrors” in detecting near fields or polaritons. We compared this two-level electron interferometry with imaging and interferometric techniques using other matter waves. When the coupling near field is quantized, we predict quantum and vacuum Rabi oscillations of the two-level electron, which can be used to investigate quantum statistics of optical excitations and electron-photon entanglement. Recent advancements in laser control of quantum electron wave packets make the experimental detection of free electron Rabi oscillations feasible. Our study may advance the understanding and applications of resonant light-matter interactions between low-energy electrons and quantum optical fields.

We introduce the dimension-restricted prepare and broadcast (PAB) scenario, which generalizes standard prepare and measure frameworks. Here, the system prepared by a sender undergoes a broadcasting transformation before being locally measured by multiple receivers. We develop a hierarchy of classical, quantum, and nonsignalling models describing this scenario, characterize their corresponding correlation sets, and derive new families of Bell-like inequalities together with linear and semidefinite programming methods for their certification. First, assuming shared randomness, we prove that the hierarchy collapses into a single set whenever we consider only one measurement per party. Then, considering multiple possible measurements, we show that PAB scenarios can activate nonclassicality of noisy broadcasting resources and can reveal preparation nonclassicality more robustly than large finite families of standard prepare and measure tests.

Long-distance entanglement distribution is hindered by photon loss in optical fibers and the no-cloning theorem. Optical quantum repeater (QR) protocols rely on Bell-state measurements (BSMs); they are intrinsically limited to probabilistic photon operations and fail 50% of the time. We propose a hybrid approach to building quantum repeaters that combines the high transmission speed of photonic qubits in optical fiber with the high-fidelity quantum processing capabilities enabled by superconducting circuits. The transduction-enabled superconducting QR (TESQR) architecture eliminates the need for probabilistic BSMs and allows deterministic processing operations. The TESQR framework always yields a final state at the remote nodes rather than aborting on photon loss, manifesting deterministic entanglement distribution within certain parameter regimes. We evaluate the performance by assessing output-state fidelities and success probabilities of entanglement distribution using realistic noise models. Additionally, we integrate an entanglement purification scheme and evaluate the performance through numerical simulations in the qutip environment. Our results show that, for entanglement swapping, the proposed scheme improves the entanglement distribution rate by an average of 63% and by up to 159% compared with photonic-only architectures. Moreover, after purification, the end-to-end fidelities exceed 0.8 over distances up to 20 km.

We introduce RAMPART-X, a quantum secret sharing framework that supports arbitrary dynamic membership under a general monotone access structure while preserving correctness, secrecy, and share invariance over time. Unlike existing approaches that treat dynamic membership, revocation, and access structure enforcement separately, our protocol integrates these features into a unified entanglement-based construction. The share generation mechanism partitions minimally qualified sets and distributes multipartite entangled states, ensuring that previously issued shares remain valid and information theoretically secure throughout system evolution. Reconstruction is achieved without secure classical channels by distributing generalized Bell states along access structure-induced paths, enabling secret recovery via chained entanglement swapping and local quantum operations. Participant revocation is modelled through partial trace, ensuring that newly formed forbidden sets obtain zero information about the secret. We further formalize a distributed dealer architecture in which the dealer generates shares and a combiner coordinates reconstruction, enhancing deployability in decentralized quantum networks. We prove correctness and unconditional security at every time epoch and show that partition independence prevents information leakage under arbitrary access-structure evolution. A proof-of-concept implementation in Python using the Cirq framework validates the protocol construction. To the best of our knowledge, RAMPART-X is the first quantum secret sharing framework to simultaneously support evolving general access structures, dynamic revocation, and entanglement-assisted reconstruction with provable information-theoretic security.

The puzzle of “sticky collisions,” in which molecular collision complexes exhibit unexpectedly long lifetimes, remains an unresolved mystery. A central challenge to solving this mystery is that traditional close-coupling calculations remain limited by the vast computational cost needed to take into account all the degrees of freedom involved in the collision. In this work, we propose a statistical model designed to simulate the result of full close-coupling calculations, with the goal of collecting statistics about reasonable lifetimes of collision complexes. To do so, we numerically sample resonances using random matrix theory and utilize results from quantum-defect theory to calculate scattering properties and lifetimes. We find that in the limit of dense resonances, our theory agrees well with the Rice-Ramsperger-Kassel-Marcus (RRKM) prediction, whereas in the limit of sparse resonances, the physics is governed by threshold behavior rather than resonant effects. By comparing these predictions to experimental results in two limits, we clarify the link between density of states and the validity of the lifetimes they predict.

We present a channel-resolved study of strong-field ionization and Coulomb explosion dynamics in ${\mathrm{H}}_2\mathrm{O}$ using real-time time-dependent density functional theory (RT-TDDFT) on a real-space grid with explicit inclusion of the driving laser field. By analyzing an ensemble of trajectories with randomized laser polarizations and thermally sampled nuclear velocities, we identify the microscopic mechanisms governing competing fragmentation pathways. Three-body fragmentation is found to dominate over undissociated and two-body channels. Fragmentation branching is determined during the early stage of the laser pulse and is strongly correlated with orbital-specific ionization. Enhanced ionization of the HOMO-2 $\left(1b_2\right)$ orbital promotes higher-ionization three-body breakup, whereas ionization dominated by the highest occupied molecular orbital (HOMO) $\left(1b_1\right)$ and HOMO-1 $\left(3a_1\right)$ favors two-body dissociation. Laser-molecule orientation plays a decisive role by selectively enhancing ionization from different molecular orbitals. The calculated kinetic-energy-release and angular distributions reproduce the principal experimental observations, while revealing that the three-body kinetic energy release is strongly correlated with the total ionization degree, confirming Coulomb repulsion as the primary determinant of the fragment energetics. These results establish a microscopic connection between orbital-specific ionization, molecular orientation, charge-state formation, and fragmentation branching, demonstrating the capability of RT-TDDFT for interpreting channel-resolved Coulomb explosion dynamics in polyatomic molecules.

In this work, we experimentally investigate different notions of nonclassicality in the simplest scenario using four preparations and two binary-outcome measurements in two distinct experimental setups that exploit different degrees of freedom of light: polarization and first-order transverse spatial modes. In addition, noise effects are explored by using an all-optical setup that reproduces the operational effect of a depolarizing channel. Our experimental approach exploits the vectorial structure of classical light, providing a reliable and highly controllable platform for investigating fundamental features arising from the Hilbert-space structure of optical modes. The experimental results are consistent with the findings of Khoshbin et al. [Phys. Rev. A 109, 032212 (2024)]: under the assumption that the two measurements performed form a tomographically complete set, the observed statistics violate their noise-robust inequalities, indicating inconsistencies with preparation noncontextuality and bounded ontological distinctness for preparations.

Generalized probabilistic theories (GPTs) provide a unifying framework encompassing classical theories, quantum theories, as well as hypothetical alternatives. We investigate both the problem of extending a system with a finite set of transformations, and the problem of adding to a translation-invariant set of systems a finite set of entangled states and effects, plus all their images under the translation symmetry. We show that determining whether such extensions are consistent with the axioms of GPTs is undecidable. The source of the undecidability is that these finite extensions can generate infinitely many conditions which must be checked: iterating transformations may produce infinitely many new transformations; similarly, entangled states and effects may generate infinitely many new states via the analog of teleportation. Our results show that extending GPTs to include dynamics or entanglement encounters fundamental computability obstructions, which can only be circumvented by introducing additional physical or mathematical assumptions.

Recent comparisons of quantum repeater protocols have highlighted the strong near-term potential of multiplexed two-way architectures for long-distance quantum communication. At the same time, advances in hollow-core fiber (HCF) technology motivate a reexamination of the physical transmission medium as an architectural lever in quantum network design. In this work we compare emerging antiresonant HCFs against conventional silica single-mode fibers (SMFs) in multiplexed two-way quantum repeater networks. We evaluate their performance under both telecom and memory-native transmission, accounting for frequency-conversion overheads, coupling efficiencies, memory decoherence, and operational noise. We find that HCF significantly outperforms SMF across a wide range of regimes. With memory-native transmission, HCF yields up to an order of magnitude improvement in secret-key rate per channel use under realistic conversion efficiencies. Even at telecom wavelengths, HCF enables larger optimal repeater spacing, improving rate-cost tradeoffs and reducing repeater requirements. We further quantify the role of memory quality, hardware efficiency, detector and conversion losses, and two-qubit gate noise in shaping these gains. These results show that recent advances in HCF materially expand the design space of practical terrestrial quantum repeater networks.

We theoretically investigate the distinct roles of magnetic dipole and electric quadrupole interactions in photoelectron momentum distributions (PMDs) arising from the strong-field multiphoton ionization of atomic hydrogen by linearly polarized, 800-nm laser pulses. By applying a Power-Zienau-Woolley-type transformation to the standard minimal-coupling Hamiltonian, we circumvent the inherent challenges associated with isolating individual nondipole contributions within conventional velocity-gauge formulations. Our ab initio simulations reveal that while both terms significantly influence the PMD, the electric quadrupole interaction becomes dominant at higher laser intensities. Crucially, we find that the magnetic dipole term induces a positive (forward) shift of the distribution peak, whereas the electric quadrupole term drives an even more pronounced negative (backward) shift. The resulting net peak shift is negative, establishing a gauge-independent physical mechanism that explains recent experimental observations.

Chern numbers are central to correlated and topological phenomena, yet most topological systems are associated with Chern numbers of order unity. Here we propose a scheme to achieve large Chern numbers in an optical Floquet quasicrystal with cold atoms, which can be directly measured via Thouless pumping. We study the quasienergy spectrum of the Floquet quasicrystal and characterize emergent Chern numbers using the gap labeling theorem. We further investigate the Thouless pumping in the Floquet quasicrystal at different driving frequencies and amplitudes, revealing the connection between transport features and the quasienergy spectrum. Our findings provide avenues for exploring rich topological dynamics in Floquet quasicrystals and realizing fractional Chern insulating states.

Topological insulators, owing to their topologically protected boundary states, hold broad application prospects in optical transmission and manipulation. This paper investigates topologically protected quantum state transfer and its acceleration under multiphoton excitation. The results show that under appropriate topological pumping, the system enables transfer between edge modes without being restricted to single excitation, facilitating topologically protected remote transfer of arbitrary quantum states. Using Gaussian states as examples, we simulate the transfer fidelities of coherent, thermal, and squeezed states, demonstrating strong robustness against disorder. To accelerate the state transfer, we introduce shortcuts to adiabaticity to control the Su–Schrieffer–Heeger (SSH) model. Under shortcuts-to-adiabatic control, the system retains topologically protected edge modes and the resulting topological pumping is no longer constrained by adiabatic conditions. Compared with the case without shortcuts, the system evolves faster in closed systems while achieving the same fidelity. In open systems the shortened evolution time enhances robustness against dissipation and thermal noise. Furthermore, we discuss alternative acceleration schemes based on partial counterdiabatic driving and pulse-shape engineering, which reduce experimental complexity by circumventing the need for full counterdiabatic control. This work advances topologically protected quantum state transfer and may offer a useful step toward high-fidelity, high-speed quantum information processing, particularly in Gaussian systems.

Photons are bosons, and yet, when prepared in specific entangled states, they can exhibit nonbosonic behavior. While this phenomenon has so far been studied in two-photon systems, exchange symmetries and interference effects in multiphoton scenarios remain largely unexplored. In this work, we show that multiphoton states uncover a rich landscape of exchange symmetries. With three photons already, multiple pairwise combinations are possible, where each pair of photons can exhibit bosonic, fermionic, or anyonic exchange symmetry. This gives rise to mixed symmetry systems that are not possible to achieve with two photons alone. We experimentally investigate how these symmetry configurations manifest in the observed interference of three photons, whereby tuning the exchange symmetry with respect to a specific photon pair controls the complete three-photon interference behavior. We show that multiphoton interference can be effectively turned on and off by tuning the symmetry of the constituent pairs. The possibility of accessing and tuning new quantum statistics in a scalable photonic platform not only deepens our understanding of quantum systems but is also highly relevant for quantum technologies that rely on quantum interference.

We propose a multiphoton heralding scheme using an optical parametric amplifier (OPA) that can generate two families of non-Gaussian states from a squeezed vacuum into: large-amplitude squeezed Schrödinger cat states and low-order parity-selective Fock superpositions. By injecting $m$ photons into the idler port and detecting $n$ photons at the output, an effective high-order photon subtraction ($k\ge 3$) can be realized in a single OPA device for properly chosen ($m, n$) pairs, with an effective order $k=m+n$. The heralded states exhibit strong Wigner negativity and high phase-space complexity. Remarkably, under photon loss, the complexity remains substantial, even after the negativity vanishes, indicating a loss-resilient quantum resource. These states exhibit phase-estimation performance that can achieve Heisenberg limit scaling with an enhanced constant factor in certain regimes. Our protocol establishes the OPA as a versatile platform for generating non-Gaussian states with promising applications in loss-resilient quantum metrology and fault-tolerant quantum information processing.