Coupled Lindblad pseudomode theory is a promising approach for simulating non-Markovian quantum dynamics on both classical and quantum platforms, with dynamics that can be realized as a quantum channel. We provide theoretical evidence that the number of coupled pseudomodes only needs to scale as $\text{polylog}(T/ϵ)$ in the simulation time $T$ and precision $ϵ$. Inspired by the realization problem in control theory, we also develop a robust numerical algorithm for constructing the coupled modes that avoid the nonconvex optimization required by existing approaches. We demonstrate the effectiveness of our method by computing population dynamics and absorption spectra for the spin-boson model. This Letter provides a significant theoretical and computational improvement to the coupled Lindblad framework, which impacts a broad range of applications from classical simulations of quantum impurity problems to quantum simulations on near-term quantum platforms.

We establish a symmetry classification for a general class of quantum feedback control. For successive feedback control with a nonadaptive sequence of bare measurements (i.e., with positive Kraus operators), we prove that the symmetry classification collapses to the ten-fold ${\mathrm{AZ}}^{†}$ classes, specifying the allowed topology of CPTP maps associated with feedback control. We demonstrate that a chiral Maxwell’s demon with Gaussian measurement errors exhibits quantized winding numbers. Moreover, for general (nonbare) measurements, we explicitly construct a protocol that falls outside the ten-fold classification. These results broaden and clarify the principles in engineering topological aspects of quantum control robust against disorder and imperfections.

Landau levels (LLs) are the massively degenerate discrete energy spectra of charged particles in a transverse magnetic field, and they lie at the heart of many intriguing phenomena, such as the integer and fractional quantum Hall effects as well as quantized vortices. In this Letter, we consider coupling of LLs of a transversely driven, single charge-neutral particle in a synthetic gauge potential to a quantized field of an optical cavity—a setting reminiscent of superradiant self-ordering setups in quantum gases. We uncover that this complex system can be, surprisingly, described in terms of two highly nonlinearly coupled quantum harmonic oscillators, thus enabling a full quantum mechanical treatment. Light-matter coupling mixes the LLs and the superradiant photonic mode, leading to the formation of hybrid states referred to as “Landau polaritons.” They partially inherit the degeneracy of the LLs and possess intriguing features such as nonzero light-matter entanglement and quadrature squeezing. Depending on the system parameters and the choice of initial state, the system exhibits diverse nonequilibrium quantum dynamics and multiple steady states with distinct physical properties. This Letter lays the foundation for further investigating the novel, driven-dissipative Landau-polariton physics in quantum-gas–cavity-QED settings.

We investigate the damage mechanisms governing crack propagation in disordered solids using random lattice models. Our simulations reveal two successive damage scaling laws at the crack tip, characterized by the coefficient of variation of the critical damage density. Close to the crack tip, the scaling exponent is $\sim -0.5$, transitioning to $\sim -0.25$ at larger distances. This transition uncovers a crack-tip equiprobable damage zone (EDZ), whose size increases with material disorder. Within the EDZ, damage exhibits statistical uniformity and the critical damage density is well approximated by a binomial distribution, reflecting the intrinsic stochasticity of fracture in disordered materials. These findings provide new physical insights into crack-tip damage and demonstrate how material disorder regulates crack propagation.

Conductive carbon additives in lithium-ion battery cathodes significantly increase electron transport, facilitating rapid charging. However, quantifying this improvement remains challenging. Momentum distribution of annihilating electron-positron pairs offers a powerful approach to selectively probe the O $2p$ orbitals in ${\mathrm{LiCoO}}_2$ microparticles and the $2p_z$ carbon orbitals in the conductive carbon additives. By analyzing this momentum distribution, we obtain the amplification of subtle electron momentum distribution signals from carbon $\pi$ bonds. Ab initio modeling of ${\mathrm{LiCoO}}_2$ and various topologies of carbon structures reproducing the experimental momentum distribution helps to quantify the fraction of positron annihilation occurring within the carbon structures. Our theoretical results combined with earlier experimental findings reveal potential charge transport pathways in the ${\mathrm{LiCoO}}_2/\mathrm{C}$ composite by quantifying the spectral contributions of electron transfer orbitals, which constitutes the nanoscale circuitry enabling efficient electron transport in battery cathodes.

Inspired by the recent experimental advances in cold atom quantum simulators, we explore the experimentally implemented bosonic $t–t^{\prime }–J$ model on the square lattice using large-scale density matrix renormalization group simulations. By tuning the doping level $\delta$ and hopping ratio $t^{\prime }/t$, we uncover six distinct quantum phases, several of which go far beyond the conventional paradigm of phase-coherent superfluidity (SF) expected for bosonic systems. In particular, in the presence of antiferromagnetic (AFM) order, doped holes are tightly bound into pairs, giving rise to a pair density wave phase at low doping and small $|t^{\prime }/t|$, which is suppressed on the $t^{\prime }<0$ side, resulting in a disordered pair density wave state that lacks coherence of either individual bosons or pairs. Upon further doping, bosons can regain phase coherence and form an SF* state, characterized by condensation at emergent incommensurate momenta concurrent with an incommensurate magnetic order. On the $t^{\prime }>0$ side, the sign-induced kinetic frustration inherently disfavors local AFM correlations, leading to a phase separation in which doped holes cluster into ferromagnetic (FM) domains spatially separated by undoped AFM regions. Upon further doping, this inhomogeneous state evolves into a uniform $\mathrm{SF}+xy$-FM phase. Finally, we propose a concrete experimental scheme to realize both signs of $t^{\prime }/t$ in Rydberg tweezer arrays, with an explicit mapping between model parameters and experimentally accessible regimes. Our results reveal competing and intertwined orders in doped antiferromagnets, which are relevant to central issues in high-$T_c$ superconductivity, reflecting the frustrated interplay between doped holes and spin background.

Quantum state purification protocols, which mitigate noise by converting multiple copies of noisy quantum states into fewer copies with a lower noise level, have applications in quantum communication and computation with imperfect devices. Here, we systematically study the task of state purification in distributed quantum systems, demanding that purification be achieved by local operations and classical communication (LOCC). We prove that, in the presence of depolarizing noise, no LOCC purification protocol starting from two copies can work blindly for all the states in three important sets: the set of all pure two-qubit states, the set of all two-qubit maximally entangled states, and the Bell basis. In stark contrast, we show that a targeted, single-state purification is always achievable in the presence of depolarizing noise, and we provide an explicit analytical LOCC protocol for every given two-qubit state. For arbitrary finite sets of pure states and arbitrary noise profiles, we develop an optimization-based algorithm that systematically designs LOCC purification protocols, and we demonstrate it through concrete examples. Overall, our results identify both fundamental limitations and practical noise-reduction strategies for distributed quantum information processing.

Quantum state purification, a process that aims to recover a state closer to a system’s principal eigenstate from multiple copies of an unknown noisy quantum state, is crucial for restoring noisy states to a more useful form in quantum information processing. Fault-tolerant quantum computation relies on stabilizer operations, which are classically simulable operations critical for error correction but inherently limited in computational power. In this Letter, we investigate the limitations of classically simulable operations for quantum state purification. We demonstrate that while certain classically simulable operations can enhance fidelity for specific noisy state ensembles, they cannot achieve universal purification. We prove that neither deterministic nor probabilistic protocols using only classically simulable operations can achieve universal two-to-one purification for qubit systems or systems of any odd dimension. We further extend this no-go result to state purification using three and four copies via semidefinite programming and numerical evidence. Our findings highlight the indispensable role of nonstabilizer resources and the inherent limitations of classically simulable operations in quantum state purification, emphasizing the necessity of harnessing the full power of quantum operations for robust quantum information processing.

We present and test a protocol to learn the matrix-product operator (MPO) representation of an experimentally prepared quantum state. The protocol takes as input classical shadows corresponding to local randomized measurements, and outputs the tensors of an MPO maximizing a suitably defined fidelity with the experimental state. The tensor optimization is carried out sequentially, similarly to the well-known density matrix renormalization group algorithm. Our approach is provably efficient under certain technical conditions expected to be met in short-range correlated states and in typical noisy experimental settings. Under the same conditions, we also provide an efficient scheme to estimate fidelities between the learned and the experimental states. We experimentally demonstrate our protocol by learning entangled quantum states of up to $N=96$ qubits in a superconducting quantum processor. Our method upgrades classical shadows to large-scale quantum computation and simulation experiments.

We propose that the broad architecture of the renormalization group flow in quantum field theories is, at least in part, fixed by unitarity. The precise statement is summarized in the unitarity flow conjecture, which states that the nonlinear $S$-matrix identities obtained by imposing unitarity imply those needed to derive the renormalization group equations. As a proof of principle, we verify this conjecture to all loops at the leading and subleading logarithmic order in the four-dimensional massless $\lambda {\varphi }^4$ theory using on-shell techniques, without reference to any counterterms or Feynman diagrams.

In an experiment performed at the Facility for Rare Isotope Beams (FRIB) using the FRIB Decay Station initiator, 15 new half-lives of isotopes near ${}^{54}\mathrm{Ca}$ were measured. A new method of extracting lifetimes from experimental data, taking into account the unknown $\beta$-delayed neutron emission branches of very neutron-rich nuclei, was developed to enable systematic uncertainty analysis. The experiment observed a dramatic change in the half-life systematics for the isotopes with neutron number $N=34$. Beyond $N=34$, the decline of nuclear lifetime is much slower, leading to longer than anticipated lifetimes for near-dripline nuclei. State-of-the-art shell-model calculations can explain the experimental results, revealing the imprint of shell effects and the need for modification of single-particle neutron states. The results from a newly developed quasiparticle random phase approximation model with potential for making global predictions were also tested against the experimental results and good agreement was found.

The triply charged thorium-229 ion (${{}^{229}\mathrm{Th}}^{3+}$) has been identified as a promising candidate for the development of ultraprecise nuclear clocks. In this Letter, we investigate how the electron structure of this ion, particularly the single valence electron, influences the nucleus through nuclear hyperfine mixing (NHM)—a phenomenon previously studied almost solely for highly charged ions. We show that NHM opens electric dipole ($E1$) transition channels, which can significantly enhance the efficiency of nuclear isomeric excitation by 2 orders of magnitude. Additionally, NHM accelerates the spontaneous decay rate of the nuclear isomeric state by 1% to 7%, depending on the specific hyperfine level involved.

Strong-field photoelectron holography (SFPH) is a powerful tool for retrieving the phase of photoelectron wave packets, offering insights into the intrinsic atomic/molecular structure and ultrafast dynamics. Here, we generalize the SFPH theory, conventionally applied to plane-phase electron wave packets, to vortex electrons. By employing a synthetic chiral atomic model with helical orbitals, we demonstrated that photoelectron holography maps the helicity of the bound states to the interference fringes and resolves enantio-sensitive phase shifts, providing direct access to the chiral information encoded in the phase of the photoelectrons. Our approach establishes a phase-sensitive diagnostic of chirality, complementary to the amplitude-based chiral spectroscopies. The intrinsic attosecond temporal resolution of SFPH further enables the measurement of ultrafast chiral electron dynamics.

We report the observation of a femtosecond strong-laser-field-ionization-induced bimolecular reaction in the acetylene dimer ${({\mathrm{C}}_2{\mathrm{H}}_2)}_2$. Single ionization by the pump laser pulse produces a bound cationic intermediate that undergoes ultrafast intermolecular rearrangement involving hydrogen migration and carbon-carbon backbone reorganization, forming a covalently bound ${\mathrm{C}}_4{\mathrm{H}}_4^{+}$ isomer. A delayed probe laser pulse drives secondary ionization, triggering further hydrogen migration and ultimately fragmenting the system into ${\mathrm{CH}}_3^{+}$ and ${\mathrm{C}}_3{\mathrm{H}}^{+}$. Time-resolved fragment yields, corroborated by molecular dynamics simulations, reveal a multistep reaction pathway characterized by bond formation and structural reorganization on the subpicosecond timescale. These results uncover a previously unobserved strong-laser-field-driven bimolecular reaction in a prototypical hydrocarbon dimer and demonstrate that time-delayed ionization provides a general route for steering chemical reactivity in weakly bound molecular systems.

We present a density matrix based time dependent projection operator formalism to calculate the beyond mean-field dynamics of systems with non-Markovian local baths and one-to-all interactions. Such models encapsulate the physics of condensed phase systems immersed in optical cavities. We use this method, combined with tensor network influence functionals, to study the dynamics of the Dicke model coupled to non-Markovian local dephasing baths at zero temperature, which has a superradiant phase transition in the mean-field limit. The method corrects a spurious initial state dependence found in the mean-field dynamics and describes the emergence of new time scales which are absent in the mean-field dynamics. Our formalism, based on density matrices, is applicable to other quantum optical systems with one-to-all interactions at finite temperatures.

The anti-$P$-pseudo-Hermitian system has recently been recognized as a new avenue in non-Hermitian physics, exhibiting symmetry-related phenomena without the need for time-reversal symmetry. However, its physical realization remains challenging due to the difficulty of integrating tunable media while simultaneously enabling nonreciprocal coupling. In this Letter, we introduce a novel framework for constructing an anti-$P$-pseudo-Hermitian mechanical system by incorporating piezoelectric actuators and sensors with nonreciprocal coupling into mechanical beams. We theoretically demonstrate that this system can exhibit programmable exceptional points (EPs) and validate our approach numerically and experimentally. Precise tuning of EPs is crucial for optimizing the system’s sensitivity under operational conditions. As a key demonstration, we show that this system excels in detecting minute mass variations, making it highly effective for ultrasensitive sensing applications. This Letter not only advances the understanding of non-Hermitian physics, but also lays the groundwork for the next generation of mechanical sensors based on EP physics.

The chemical environment at interfaces plays an important role in controlling the structure, properties, and performance of low-dimensional materials. The water environment and adsorbates on solid surfaces are the most common interface environments that are prevalent in nonultrahigh vacuum conditions. Despite their ubiquitous presence, the structural and dynamic properties of these surface adsorbates are difficult to be directly characterized in situ at the atomic scale. Here, we report a dissection method leveraging shallow nitrogen-vacancy centers to quantitatively characterize nanoscale adsorbate layers on diamond surfaces with distinct structural and dynamical signatures. Our results reveal that under ambient conditions, a tightly bound organic adsorbate layer and an icelike interfacial water layer coexist on diamond surfaces. We further demonstrate that the rigidity of the interfacial water layer originates from its interaction with specific surface adsorption sites, such as the dangling bonds on the diamond surface. These findings establish new insights for investigating the structure and dynamics of low-dimensional adsorbates, as well as surface properties modulated by adsorbates under native conditions.