Quantum computation with electron spin qubits requires coherent and efficient manipulation of these spins, typically accomplished through the application of alternating magnetic or electric fields for electron spin resonance. In particular, electrical driving allows us to apply localized fields on the electrons, which benefits scale-up architectures. However, we have found that Electric Dipole Spin Resonance is insufficient for modeling the Rabi behavior in recent experimental studies. Therefore, we propose that the electron spin is being driven by a method of electric spin qubit control that generalizes the spin dynamics by taking into account a quadrupolar contribution of the quantum dot: electric quadrupole spin resonance. In this work, we explore the electric quadrupole driving of a quantum dot in silicon, specifically examining the cases of 5 and 13 electron occupancies.

We introduce a quantum spin van der Pol (vdP) oscillator as a prototypical model of quantum spin-based limit-cycle oscillators, which coincides with the quantum optical vdP oscillator in the high-spin limit. The system is described as a noisy limit-cycle oscillator in the semiclassical regime at large spin numbers, exhibiting frequency entrainment to a periodic drive. Even in the smallest spin-1 case, mutual synchronization, Arnold tongues, and entanglement tongues in two dissipatively coupled oscillators, and collective synchronization in all-to-all coupled oscillators are clearly observed. The proposed quantum spin vdP oscillator will provide a useful platform for analyzing quantum spin synchronization.

Dimensionality and electronic correlations are crucial elements of many quantum material properties. An example is the change of the electronic structure accompanied by the loss of quasiparticles when a metal is reduced from three dimensions to a lower dimension, where the Coulomb interaction between carriers becomes poorly screened. Here, using angle-resolved photoemission spectroscopy, we report an orbital-selective decoherence of spectral density in the perovskite nickelate $\mathrm{LaNi}{\mathrm{O}}_3$ toward the monolayer limit. The spectral weight of the $d_{z2}$ band vanishes much faster than that of the $d_{x2-y2}$ band as the thickness of the $\mathrm{LaNi}{\mathrm{O}}_3$ layer is decreased to a single unit cell, indicating a stronger correlation effect for the former upon dimensional confinement. Dynamical mean-field theory calculations show an orbital-selective Mott transition largely due to the localization of $d_{z2}$ electrons along the $c$ axis in the monolayer limit. This orbital-selective correlation effect underpins many macroscopic properties of nickelates, such as metal-to-insulator transition and superconductivity, where most theories are built upon a $d_{x2-y2}\text{–}{d}_{z2}$ two-band model.

Quantum memristors represent a promising interface between quantum and neuromorphic computing, combining the nonlinear, memory-dependent behavior of classical memristors with the properties of quantum states. An optical quantum memristor can be realized with a vacuum-one-photon qubit entering a tunable beam splitter whose reflectivity is adapted according to the mean number of photons in the device. In this work, we report on the experimental implementation of a bulk quantum-optical memristor, working with single-rail coherent superposition states in the Fock basis, generated via a resonantly excited quantum dot single-photon source. We demonstrate that the coherence of the input state is preserved by the quantum memristor. Moreover, our modular platform allows investigating the nonlinear behavior arising from a cascade of two quantum memristors, a building block for larger networks of such devices toward the realization of complex neuromorphic quantum architectures.

Magic, or nonstabilizerness, is a crucial quantum resource, yet its dynamics in open quantum systems remain largely unexplored. We investigate magic in the open XXZ spin chain under either boundary gain and loss or bulk dephasing using the stabilizer Rényi entropy $M_2$. To enable scalable simulations of large systems, we develop a unique, highly efficient algorithm for computing $M_2$ within the matrix product state formalism while maintaining constant bond dimension—an advancement over existing methods. For boundary driving, we uncover universal scaling laws, $M_2\left(t\right)\sim t^{1/z}$, linked to the dynamical exponent $z$ for several distinct universality classes. We also disentangle classical and quantum contributions to magic by introducing a mean-field approximation for magic, thus emphasizing the prominent role of quantum-critical fluctuations in nonstabilizerness. For bulk dephasing, dissipation can transiently enhance magic before suppressing it and drive it to a nontrivial steady-state value. These findings position magic as a powerful diagnostic tool for probing universality and dynamics in open quantum systems.

We document a field experiment in which a path to strongly interacting soliton gas dynamics is observed within an intermittently open/closed estuary. We show that the shallow estuary mouth acts as a low-pass filter for incoming ocean waves, damping energy within the swell frequency band (0.04–1 Hz) and allowing surf-zone generated infragravity waves (frequency band 0.004–0.04 Hz) to enter the semienclosed shallow lagoon formed near the estuary mouth. These long waves penetrate under highly nonlinear conditions with Ursell numbers consistent with multisoliton fission regimes. The $k\text{–}\omega$ spectrum of the incident wave trains is consistent with solitonic kinematics, demonstrating that solitons are released by the fission of incoming infragravity waves at the lagoon entrance. Continuous injection of solitonic wave trains and intense wave-wave interactions enhanced by the shallow and gradually varying bathymetry within the estuary lagoon lead to a quasistationary soliton gas regime with a substantially increased probability of rogue wave occurrence compared with linear wave theory. The Korteweg-de Vries nonlinear Fourier transform reveals that nearly half of the measured signal energy is explained by solitonic modes, confirming the key role that solitons have in enhancing rogue wave emergence in natural coastal settings.

Two-photon interference (TPI) underpins many photonic quantum technologies and is commonly regarded as a quantum effect requiring indistinguishable photons. Here, we demonstrate TPI between single photons with ultralong coherence time and an independent continuous-wave laser. The measurements reveal a sharp antibunching dip, governed by the single-photon correlation time, together with a broad Hong-Ou-Mandel dip whose half-width is set by the mutual coherence time of the two sources. We achieve a maximum TPI visibility of $72\pm 2\%$, well above the $50\%$ classical limit, thereby confirming the quantum nature of TPI. At the same time, we observe a broad visibility background and a beat visibility below $50\%$, signatures of classical interference. Both quantum and classical visibility features remain unchanged for frequency separations up to ${10}^4$ times the linewidth of the single photons, showing no distinction between distinguishable and indistinguishable photons. By applying both general wave superposition theory and a quantum field approach, we derive the same cross-correlation functions that quantitatively reproduce the data. Our results show that quantum and classical features of TPI originate from the same underlying fourth-order interference process arising from second-order interference within the mutual coherence time. Photon indistinguishability is a sufficient condition for TPI to occur, but not a necessary one. This insight offers different perspectives for the development of quantum photonic technologies based on independent photons.

In contrast to ultracold atomic gases, Fermi-Bose crossover in solid-state superconductors is rare and a relatively recent observation. We report the first theoretical proposal of disorder-tuned Fermi-Bose crossover in superconductors with a customized spin-selective disorder potential serving as the control parameter. Our analysis of the relevant spectroscopic signatures unambiguously brings forth the evolution of the Fermi surface topology with disorder, as the system traverses through the Fermi-Bose crossover. We qualitatively analyze our inferences in the light of the recent observations of Fermi-Bose crossover in doped iron chalcogenide superconductors and organic superconductors, as well as propose an experimental setup of two-dimensional electron gas at oxide interfaces where such disorder-tuned Fermi-Bose crossover could be observed.

We report the measurement of the ionization energy of the ${}^{85}\mathrm{Rb}_2$ molecule through resonantly enhanced two-photon ionization in a supersonic beam. The first photon excites the $X^1{\mathrm{\Sigma }}_g^{+}(v_X=0)\to B^1{\mathrm{\Pi }}_u(v_B=2)$ transition, while the second photon wave number is scanned over the $16730–16755{\mathrm{cm}}^{-1}$ range, thus yielding a structured spectrum of ${\mathrm{Rb}}_2^{+}$ ions extracted by an electric field and recorded by mass spectrometry. We modeled the onset of the ionization signal as a function of the electric field strength between 18 and 180 V/cm, leading to the ${\mathrm{Rb}}_2$ ionization energy $E_i=31497.3\pm 0.6{\mathrm{cm}}^{-1}$ and to the dissociation energy of the ${\mathrm{Rb}}_2^{+}$ ground state $D_0=6158.2\pm 0.6{\mathrm{cm}}^{-1}$. Our measured value $E_i$ is found to be $149.3{\mathrm{cm}}^{-1}$ larger than the one reported in the experiment by Bellos et al. [Phys. Rev. A 87, 012508 (2013)]. Our value of $D_0$ agrees with our theoretical determination using a quantum chemistry approach. Using a simple theoretical model, we assign unevenly spaced structures of the ionization spectrum to molecular Rydberg levels belonging to several series that converge to the lowest vibrational levels of ${\mathrm{Rb}}_2^{+}$.

We study an $SU\left(3\right)$-invariant Fermi-Hubbard gas undergoing on-site three-body losses. The model presents eight independent strong symmetries preventing the complete depletion of the gas. By making use of a basis of semistandard Young tableaux states, we reveal the presence of a rich phenomenology of stationary states. We classify the latter according to the irreducible representation of $SU\left(3\right)$ to which they belong. We finally discuss the presence of three-particle stationary states that are not protected by the $SU\left(3\right)$ symmetry.

We theoretically investigate excitation dynamics in one-dimensional arrays of quantum emitters coupled to a waveguide, focusing on localization and long-time population trapping. By combining time-domain simulations with spectral analysis of an effective non-Hermitian Hamiltonian, we identify two distinct mechanisms that give rise to localization: geometry-induced subradiance and disorder-induced Anderson-like confinement. Spatially modulated emitter arrangements—such as single- and double-Gaussian transverse profiles—enable long-lived subradiant modes even in the absence of disorder, with decay rates that can be finely controlled via geometric parameters. In contrast, localization in uniform arrays emerges only when disorder breaks spatial symmetry and suppresses collective emission through interference. We track the crossover between geometric and disorder-induced regimes, finding that double-Gaussian profiles exhibit clear spatial signatures of this transition, while single-Gaussian configurations display more gradual changes. These results establish geometry and disorder as complementary tools for engineering long-lived quantum states in waveguide QED systems, with direct relevance for scalable implementations in photonic platforms.

We show that a random light field can be harnessed for high-precision metrology by introducing specific boundary conditions in the form of Lambertian reflections inside a cavity. We demonstrate a quantifiable and reproducible interferometric response to minute perturbations in wavelength, refractive index, and geometry, predicting high sensitivities consistent with experimental measurements of geometrical deformations down to the picometer scale.

We investigate the theory of surface plasmon polaritons on a magnetic Weyl semimetal conical tip. We show that the axion term in the effective electrodynamics modifies the surface plasmon polariton dispersion relation and allows all modes with a given sign of the orbital angular momentum to be focused at the end of the tip. This is in contrast with normal metals, in which only one mode can reach the end. We discuss how this orbital angular momentum nanofocusing expands the potential of technologies that use this degree of freedom.

Levitated systems have great potential in quantum sensing and exploring fundamental physics at the macroscopic scale. Of particular interest are recent works suggesting that a levitated ferromagnet can beat the standard quantum limit of magnetometry, a benchmark for quantum sensors. In this work, we show how a microscopic theory capturing atomic-scale spin-lattice interactions can be used to fully explain the emergence of collective precession dynamics of a levitated ferromagnet and the origin of its enhanced magnetometric sensitivity beyond that of independent spins. Our theory further takes us to two innovative experimental designs of immediate interest: measurement of the celebrated Berry phase with a precessing ferromagnetic needle and the use of its nutation motion to sense a low-frequency oscillating magnetic field. With a microscopic theory established for levitated ferromagnetic needles, future studies of macroscopic quantum effects and the associated quantum-classical transition also become possible.

We study a quantum system that consists of two fermionic chains coupled by a driven quantum point contact (QPC). The QPC contains a bond with a periodically varying tunneling amplitude. Initially, the left chain is packed with fermions, while the right one is empty. We numerically track the evolution of the system and demonstrate that, at frequencies above a certain threshold, the current through the QPC halts, and the particle imbalance between the chains remains forever. This implies a spectacular breakdown of the Floquet version of the eigenstate thermalization hypothesis that predicts a homogeneous particle density profile at large times. We confirm the effect for various driving protocols and interparticle interactions.

We build Floquet-driven capacitive circuit networks to realize topological states of matter in the frequency domain. As visible through our Floquet Laplacian formalism, the intertwining of static circuit components and parametric Floquet driving effectively creates a barrier in the frequency dimension, allowing to resolve the bulk-boundary correspondence of Floquet topological matter. By implementing a Su-Schrieffer-Heeger Floquet lattice model and measuring the associated circuit Laplacian and characteristic resonances, we demonstrate Floquet topological edge modes emerging at this frequency space barrier. Floquet circuits allow for the creation of topological phenomena in synthetic frequency dimensions with just a single unit cell of time-variable circuit components.