Squeezed states play a key role in diverse frontiers of quantum physics. Geometrically squeezed states, squeezed states in the orbital phase space of rotating Bose-Einstein condensates (BECs), have been conventionally generated by anisotropic-trapping potentials. In this work, we propose a different route to generate geometric squeezing via spin-orbit coupling (SOC) in a pseudospin-1/2 BEC. We show that the SOC enables effective two-phonon transitions within the lowest Landau level via virtual spin-flip processes, leading to exponential squeezing dynamics in both spin components. Furthermore, by applying a $\pi /2$ spin rotation, the two spin channels can be coherently coupled to produce two-mode geometric squeezing. We also investigate the influence of interatomic interactions on squeezing performance and identify parameters where robust squeezing can be achieved. Our work provides a viable pathway to realize and manipulate geometric squeezing in spinor quantum gases.

We study a repumping transition for ${}^{88}\mathrm{Sr}$ atoms trapped in a blue magneto-optical trap. We show that, while the repumping efficiency is about three orders of magnitude smaller than for traditional schemes, it is sufficient for recycling all atoms, provided the repumping laser beams are arranged to form a green magneto-optical trap (MOT) helping to cool and confine the atoms and preventing their loss. Our main findings are the following: (i) that the green MOT configuration is able to trap ten times more atoms in the blue MOT than using the “green” transition merely as a repump, and (ii) that the population transfer between the two MOTs of the two-color scheme can be controlled through experimental control parameters. The interest of this scheme lies in its capability of reaching sub-Doppler temperatures and its suitability for continuous atomic beam generation.

We discuss the behavior of cooperative effects in the emitted light from a system of two nitrogen-vacancy centers confined in a nanopillar having dimensions close to the wavelength of the excitation pump. We experimentally observe a $g^{\left(2\right)}\left(0\right)>0.5\to 1$ for the coupled emitter system and a drastic decrease in the singlet and triplet transition rates increase by a factor of approximately 6, indicating an interaction between the two emitters, which indicates superradiant behavior. We theoretically study the dissipative dynamics of the interaction of the emitter system with the excitation light at a finite temperature for three cases (a single emitter and two emitters with and without dipole-dipole coupling) by solving the Lindblad master equation and providing an analytical expression for the second-order correlation function. Through this, we support our experimental results and discuss superradiance from our system.

In the vicinity of a phase transition ergodicity can be broken. Here, different initial many-body configurations evolve toward one of several fixed points, which are macroscopically distinguishable through an order parameter. This mechanism enables state classification in quantum cellular automata and feedforward quantum neural networks. We demonstrate that this capability can be efficiently learned from training data even in extremely high-dimensional state spaces. We illustrate this using a quantum cellular automaton that allows binary classification, which is closely connected to the dynamics of a ${\mathbb{Z}}_2$-symmetric Ising model with local interactions and dissipation. This approach can be generalized beyond binary classification and offers a natural framework for exploring the link between emergent many-body phenomena and the interpretation of data processing capabilities in the context of quantum machine learning.

We investigate the emergence of synchronization blockade arising from the combined action of external driving and internal exchange interactions in quantum oscillators. The external drive indirectly influences the undriven mode through coupling to the driven mode, leading to a breakdown of limit cycle behavior in the Wigner function. Concurrently, the interplay of driving and coupling transforms dressed-state peaks into a Mollow-like triplet in the power spectrum. An asymmetric synchronization blockade is revealed in the phase measures, where the undriven mode remains phase locked to the drive even when the driven mode is at blockade. Using the relative entropy of coherence, we establish that resonant blockade is associated with the suppression of coherence due to the competing effects of drive-induced coherence and its redistribution via exchange interactions.

We introduce new algorithms and provide example constructions of stabilizer models for the gapped boundaries, domain walls, and $0\text{D}$ defects of Abelian composite-dimensional twisted quantum doubles. Using the physically intuitive concept of condensation, our algorithm explicitly describes how to construct the boundary and domain-wall stabilizers starting from the bulk model. This extends the utility of Pauli stabilizer models in describing nontranslationally invariant topological orders with gapped boundaries. To highlight this utility, we provide a series of examples, including a new family of quantum error-correcting codes where the double of ${\mathbb{Z}}_4$ is coupled to instances of the double semion (DS) phase. We discuss the codes' utility in the burgeoning area of quantum error correction with an emphasis on the interplay between deconfined anyons, logical operators, error rates, and decoding. We also augment our construction, built using algorithmic tools to describe the properties of explicit stabilizer layouts at the microscopic lattice level, with dimensional counting arguments and macroscopic-level constructions building on pants decompositions. The latter outlines how such codes' representation and design can be automated. Our results are validated by a series of error-correcting threshold calculations comparing our codes' performance with that of standard surface codes. To do so, we introduce a composite-dimensional belief-propagation decoder with ordered statistics that utilizes combination sweeps. Going beyond our worked-out examples, we expect our explicit step-by-step algorithms to pave the path for higher-dimensional codes to be discovered and implemented in near-future architectures that take advantage of various hardware platforms.

Existing quantum speed limits for controlled open quantum systems depend on the specified trajectory. For example, lower bounds on quantum annealing times in the presence of dissipation depend explicitly on the chosen annealing schedule. Recently, schedule-independent speed limits have been derived for annealing in the closed quantum system setting [L. P. García-Pintos et al., SciPost Phys. 18, 159 (2025)]. In this work, we generalize these results to open quantum systems, deriving schedule-independent lower bounds for quantum annealing times in systems described by a Lindblad master equation. We analyze the interplay between coherent control and dissipation in single- and two-qubit examples, demonstrating that the derived lower bounds capture key scaling behavior with respect to the strength of the dissipator. Finally, we apply the bound to thermal state preparation and show that the bound matches the expected asymptotic behavior for an Ising model in the high-temperature limit.

A quantum network is a network of entangled states which can be used to transmit quantum information. Nonmaximally entangled states are not really effective in establishing quantum communication across vast distances. Creating and maintaining a maximally entangled state over which quantum information can be transferred more effectively is difficult in experiments, as nonmaximally entangled states are typically produced therein. Therefore, we usually construct a network of nonmaximally entangled states and use the underlying network structure to establish maximal entanglement between distant nodes. Various protocols leveraging interesting aspects of quantum and statistical physics are designed to achieve long-range maximally entangled states. Here, we consider two-dimensional lattices as quantum networks where edges represent nonmaximally entangled pure states. We introduce a general protocol based on bond percolation—general concurrence percolation (GCP)—to create a network of maximally entangled states. The associated network obtained through GCP ought to enable the achievement of long-range quantum communication. Our observations indicate that, similar to other existing protocols, GCP falls within the percolation universality class, as determined through finite-size scaling analysis performed on two-dimensional lattices. We find that the associated percolation threshold value is smaller than that of the existing protocols. We introduce and analytically solve a minimal model that renders insight into the origin of the fundamentally lower percolation threshold achieved by GCP.

Quantum Random Access Codes (QRACs) embody the fundamental trade-off between the compressibility of information into limited quantum resources and the accessibility of that information, serving as a cornerstone of quantum communication and computation. In particular, the $(n,n-1)$-QRACs, which encode $n$ bits of classical information into $n-1$ qubits, provides an ideal theoretical model for verifying quantum advantage in high-dimensional spaces; however, the analytical derivation of codes saturating the conjectured bound for general $n$ has remained an open problem. In this paper, we establish an analytical construction method for $(n,n-1)$-QRACs by using an explicit operator formalism. We prove that this construction strictly achieves the numerically conjectured upper bound of the average success probability, $\mathcal{P}=1/2+\sqrt{(n-1)/n}/2$, for all $n$. Furthermore, we present a systematic algorithm to decompose the derived positive-operator-valued measure saturating this bound into standard quantum gates. Since the resulting decoding circuit consists solely of interactions between adjacent qubits, it can be implemented with a circuit depth of $O\left(n\right)$ even under linear connectivity constraints. Additionally, we analyze the high-dimensional limit $n\to \infty$ and demonstrate that while the noncommutativity of measurements is weakened, an information-theoretic gap of $O\left({log}_{2}n\right)$ from the mutual-information bound inevitably arises for symmetric encoding. This study not only provides a scalable implementation method for high-dimensional quantum information processing but also offers new insights into the mathematical structure at the quantum-classical boundary.

We calculate parity-violation-induced $E1$ amplitudes for the $1s\to 2s$ and $1s^{2}2s\to 1s^{2}3s$ transitions in H- and Li-like ions of ${}^{40}\mathrm{Ca}, {}^{48}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$. In our analysis, we account for neutron skin effects and nuclear uncertainties for each nucleus. We consider the spin-independent weak-interaction contribution of the $Z^0$ boson described by the standard model, as well as the effects of a hypothetical new $Z^{\prime }$ boson of varying mass. We conclude that the neutron-skin corrections in the ${}^{40,48}\mathrm{Ca}$ isotope pair can mostly be neglected when considering $Z^{\prime }$ boson effects, which is an advantage for the search for new parity-violating physics. However, both the neutron skin effect and the sensitivity to hypothetical $Z^{\prime }$ interactions in ${}^{208}\mathrm{Pb}$ are shown to be significant.

Multipartite entanglement is an essential quantum resource for various distributed quantum applications. One promising method for preparing multipartite entanglement is to interfere independent photons at linear-optical interference setups. While heralding the successful interference and thereby the state generation is often costly, postselecting entangled states provides an achievable alternative in this framework. We introduce a family of interference schemes for postselecting symmetric qudit Dicke states, useful resources in quantum communication and variational quantum computing. We present schemes with and without ancillary photons and show that using ancillary photons can exceed the upper bound on the success probability of schemes without ancillary photons. Our results accommodate a wide range of linear-optical schemes, providing multiple viable approaches for postselecting Dicke states.

We consider discrete spacetime models known as quantum walks, which can be used to simulate Dirac particles. In particular, we look at fermion doubling in these models, in which high-momentum states yield additional low-energy solutions which behave like Dirac particles. The presence of doublers carries over to the "second-quantized" version of the walks represented by quantum cellular automata, which may lead to spurious solutions when introducing interactions. Moreover, we also consider pseudodoublers, which have high energy but behave like low-energy Dirac particles, and cause potential problems regarding the stability of the vacuum. To address these issues, we propose a family of quantum walks that are free of these doublers and pseudodoublers but still simulate the Dirac equation in the continuum limit. However, there remain a small number of additional low-energy solutions which do not directly correspond to Dirac particles. While the conventional Dirac walk always has a zero probability for the walker staying at the same point after a single time step, we obtain the family of walks by allowing this probability to be nonzero.

The paradigm in which gravity can generate entanglement between distant masses represents a profound shift in our understanding of quantum-gravitational interfaces and is still among the active and debated topics. Recent work [A. ur Rahman et al., Phys. Rev. D 111, 064077 (2025)] established gravitational cat states as robust carriers of quantum correlations under thermal and classical fields. In our work, we demonstrate their capacity to stabilize quantum resources under a dissipative environment, which is the dominant decoherence mechanism in engineered platforms such as superconducting qubits. By incorporating both gravitational-like and spin-orbit couplings in a Markovian open system, we analytically demonstrate that quantum correlations attain nonvanishing steady-state values, and the stationary fidelity is enhanced by increasing the gravitational-like coupling. The spin-orbit interaction drives Rabi-like oscillations that counteract monotonic decay, and the gravitational coupling mimics non-Markovian memory, enabling long-term information stability. These mechanisms position gravity-inspired interactions not merely as entanglement generators, but as active stabilizers of quantumness in realistic dissipative environments.

We establish a rigorous framework that identifies imaginarity as a fundamental resource inherent in quantum coherence. By means of a geometric decomposition, we partition coherence into distinct imaginarity and residual components, thereby revealing a universal hierarchical relationship among these resources. For bipartite systems, this decomposition provides explicit bounds on the extent to which nonlocal correlations and imaginarity limit local coherence generation. Furthermore, we devise an explicit operational protocol that converts imaginarity into usable coherence, demonstrating the direct interconvertibility of these resources under physically admissible operations. The dynamical evolution under diagonal Hamiltonians is fully characterized, showing that while total coherence is conserved, imaginarity and residual coherence exhibit complementary oscillations. Our results provide a rigorous geometric and operational characterization of imaginarity as a fundamental constituent of quantum coherence, offering concrete insights for resource management in distributed quantum technologies. The geometric framework and theoretical bounds established herein are fully general, while the explicit conversion protocol and dynamical analysis serve as a compelling proof-of-principle demonstration in qubit systems.

Since precisely controlling dissipation in realistic environments is challenging, digital simulation of the Lindblad master equation (LME) is of great significance for understanding nonequilibrium dynamics in open quantum systems. However, achieving long-time simulations for complex systems with multiple dissipation channels remains a major challenge, both theoretically and experimentally. Here, we propose a 1-dilation digital scheme for simulating the LME based on quantum trajectory averaging without postselection. By rigorously matching the stochasticity inherent in quantum trajectories with the probabilistic outcomes of quantum measurements, our method effectively translates the classically established quantum jump algorithm into executable quantum circuits. A key advantage of our method is that it overcomes the exponential suppression of success probability seen in some existing postselection-dependent schemes, especially for long-time evolution or systems with numerous jump operators. Moreover, the scheme can be extended to a 2-dilation framework for the nonlinear LME with postselection, bridging the full LME and non-Hermitian Hamiltonian dynamics. This extended scheme provides a digital approach for exploring the interplay between non-Hermitian Hamiltonians and dissipative terms within a monitored quantum dynamics framework.

Entanglement cohomology assigns a graded cohomology ring to a multipartite pure state, providing homological invariants that are stable under local unitaries and characterize inequivalent patterns of entanglement. In this work we derive exact expressions for the dimensions of these cohomology groups in two canonical entanglement classes, generalized GHZ and W states on an arbitrary number of parties and local Hilbert space dimensions, thus proving the conjectures of arXiv:1901.02011. Using the additional structure of the Hodge star and wedge product operations, we propose two classes of local unitary invariants: the spectrum of the natural Laplacian acting on entanglement $k$-forms and the intersection numbers obtained from wedge products of representatives for cohomology classes. We present numerical studies which investigate these invariants in particular states, suggesting that they may provide useful quantities for describing multipartite entanglement.

Time crystals, with their intrinsic long-range temporal order and self-sustained oscillations, provide a unique platform for quantum applications that leverages long-lived coherence. We investigate the emergence of time-crystalline order in a continuously driven, dissipative atomic lattice featuring spatially inhomogeneous atom-atom interactions. The spatial dependence of these interactions spontaneously breaks the dynamical equivalence among lattice sites, resulting in the formation of distinct atomic subpopulations that exhibit unequal temporal responses. This spatially induced inequivalence lifts effective degeneracies within the driven system, thereby enabling the spontaneous breaking of continuous time-translation symmetry. As the driving strength is increased, the system undergoes a rich sequence of nonequilibrium dynamical regimes, including bistability, chaotic behavior, a stable time-crystalline phase, quasiperiodic dynamics, and ultimately an approach to a dynamical steady state. We further demonstrate that controlled initial inequivalence between atom ensembles significantly enhances the robustness of the time-crystalline phase. The interplay of detuning, interaction strength, and dissipation in either stabilizing or suppressing the emergent temporal order is systematically analyzed. This work suggests that spatial engineering of nonlinearities can serve as a design principle for generating temporal order within a mean-field description of driven quantum systems.

The intercorrelation level among constituent electrons of a multielectronic system is quantified by comparing the electron-pair density and the product of its marginal one-particle densities. The resulting comparison is interpreted as a measure of the interelectronic correlation and/or mutual information. Earlier studies on this line are well known, here extended by considering generalized comparative functionals, particularly Jensen-Tsallis and Jensen-Rényi divergences, as well as the generalized quantum similarity index. Applications within the present paper are focused on the analysis of nonheavy atomic systems, dealing with both neutral and ionized species at position and momentum spaces. Main conclusions are grounded on the fundamental role played by the shell structure to highly determine, or condition at least, the electron correlation of the systems considered here.