Intercalation is a robust method for tuning the physical properties of a vast number of van der Waals (vdW) materials. However, the prospects of using intercalation to modify magnetism in van der Waals (vdW) systems and the associated mechanisms have not been adequately studied. In this work, we modulated magnetic order in XY antiferromagnet NiPS₃ single crystals by introducing pyridine molecules into the vdW’s gap under different thermal conditions. X-ray diffraction measurements indicated pronounced changes in the lattice parameter β, while magnetization measurements at in-plane and out-of-plane configurations exposed reversal trends in the crystals’ Néel temperatures through intercalation/deintercalation processes. The changes in magnetic ordering were also supported by three-dimensional thermal diffusivity experiments. The preferred orientation of the pyridine dipoles within the vdW gaps was deciphered via polarized Raman spectroscopy. The results highlighted the relationship between the preferential alignment of the intercalants, thermal transport, and crystallographic disorder, along with the modulation of anisotropy in the magnetic order. DFT + U calculations indicated that the varying interlayer exchange interactions, regulated by intercalants, were responsible for modulating samples’ magnetic ordering. The study uncovers the possible merit of intercalation for manipulating spin orientations in spin electronics and advanced quantum devices.

Spatial photonic Ising machines (SPIMs) are promising computation devices that can be used to find the ground states of different spin Hamiltonians and solve large-scale optimization problems. The photonic architecture leverages the matrix multiplexing ability of light to accelerate the computing of spin Hamiltonian via free space light transform. However, the intrinsic long-range nature of spatial light only allows for uncontrolled all-to-all spin interaction. We explore the ability to establish arbitrary spin Hamiltonian by modulating the momentum of light. Arbitrary displacement-dependent spin interactions can be computed from different momenta of light, formulating as a generalized Plancherel theorem, which allows us to implement a SPIM with a minimal optical operation (that is, a single Fourier transform) to obtain the Hamiltonian of customized spin interaction. Experimentally, we unveil the exotic magnetic phase diagram of the generalized J1-J2-J3 model, shedding light on the ab initio magnetic states of iron chalcogenides. Moreover, we observe Berezinskii-Kosterlitz-Thouless dynamics by implementing an XY model. We open an avenue to controlling arbitrary spin interaction from the momentum space of light, offering a promising method for on-demand spin model simulation with a simple spatial light platform.

Quantum nanophotonics offers essential tools and technologies for controlling quantum states, while maintaining a miniature form factor and high scalability. For example, nanophotonic platforms can transfer information from the traditional degrees of freedom (DoFs), such as spin angular momentum (SAM) and orbital angular momentum (OAM), to the DoFs of the nanophotonic platform - and back, opening new directions for quantum information processing. Recent experiments have utilized the total angular momentum (TAM) of a photon as a unique means to produce entangled qubits in nanophotonic platforms. Yet, the process of transferring the information between the free-space DoFs and the TAM was never investigated, and its implications are still unknown. Here, we reveal the evolution of quantum information in heralded single photons as they couple into and out of the near-field of a nanophotonic system. Through quantum state tomography, we discover that the TAM qubit in the near-field becomes a free-space qudit entangled in the photonic SAM and OAM. The extracted density matrix and Wigner function in free-space indicate state preparation fidelity above 97%. The concepts described here bring new concepts and methodologies in developing high-dimensional quantum circuitry on a chip.

Probing coherent quantum dynamics in light–matter interactions at the microscopic level requires high-repetition-rate isolated attosecond pulses (IAPs) in pump–probe experiments. To date, the generation of IAPs has been mainly limited to the kilohertz regime. In this work, we experimentally achieve attosecond control of extreme-ultraviolet (XUV) high harmonics in the wide-bandgap dielectric MgO, driven by a synthesized field of two femtosecond pulses at 800 and 2000 nm with relative phase stability. The resulting quasi-continuous harmonic plateau with ∼9 eV spectral width centered around 16.5 eV photon energy can be tuned by the two-color phase and supports the generation of an IAP (∼700 attoseconds), confirmed by numerical simulations based on the three-band semiconductor Bloch equations. Leveraging the high-repetition-rate driver laser, the moderate intensity requirements of solid-state high-harmonic generation, and band-structure-induced spectral enhancement, we achieve IAP production at an unprecedented megahertz repetition rate, paving the way for compact all-solid-state XUV sources for IAP generation.

The study of van der Waals heterostructures with an interlayer twist, known as twistronics, has been instrumental in advancing the understanding of many strongly correlated phases, many of which derive from the topology of the physical system. Here we explore the application of the twistronics paradigm in plasmonic systems with a non-trivial topology by creating a moiré skyrmion superlattice using two superimposed plasmonic skyrmion lattices with a relative twist. We measure the complex electric field distribution of the moiré skyrmion superlattice using time-resolved polarimetric photoemission electron microscopy. Our results show that each supercell has very large topological invariants and harbours a skyrmion bag, the size of which is controllable by the twist angle and centre of rotation. Our work indicates how twistronics can enable the creation of various topological features in optical fields and provides a route for locally manipulating electromagnetic field distributions.

Quantum dots host short- and long-lived bright and dark excitons (DEs). The long-lived DEs form coherent integer-spin qubits that can be written, controlled, read, and reset using single picosecond optical pulses. These qubits enable the deterministic generation of multi-entangled photon clusters, crucial for quantum communication. With nondegenerate eigenstates, DEs exhibit a natural precession in their coherent superposition, which can challenge qubit control. The authors present here experimental and theoretical methods to reduce and eliminate this precession, while discovering the polarization of this optically inactive qubit.

Open quantum systems that comply with the master equation and detailed balance decay in a non-oscillatory manner to thermal equilibrium. Beyond the weak coupling limit, systems that break microreversibility (e.g., in the presence of magnetic fields) violate detailed balance but still thermalize. We study the thermalization of these systems and show that a temperature increase produces novel exceptional points that indicate a sharp transition in the thermalization dynamics. A further temperature increase fuels oscillations of the energy level populations, even without quantum coherences. Moreover, the violation of detailed balance introduces an energy scale that characterizes the oscillatory regime at high temperatures.

PAX (antiProtonic Atom X-ray spectroscopy) is a new experiment with the aim to test strong-field quantum electrodynamics (QED) effects by performing high-precision x-ray spectroscopy of antiprotonic atoms. By utilizing advanced microcalorimeter detection techniques and a low-energy antiproton beam provided by the ELENA ring at CERN, gaseous targets will be used for the creation of antiprotonic atoms, and the measurement of transitions between circular Rydberg states will be conducted with up to two orders of magnitude improved accuracy over previous studies using high-purity germanium detectors. Our approach eliminates the longstanding issue of nuclear uncertainties that have hindered prior studies using highly charged ions, thus enabling direct and purely QED-focused measurements. By precisely probing atomic systems with electric fields up to two orders of magnitude above the Schwinger limit, PAX will test vacuum polarization and second-order QED corrections, opening new frontiers in fundamental physics and uncovering potential pathways to physics beyond the Standard Model.

Quantum simulators hold promise for solving many intractable problems. However, a major challenge in quantum simulation, and quantum computation in general, is to solve problems with limited physical hardware. Currently, this challenge is tackled by designing dedicated devices for specific models, thereby allowing to reduce control requirements and simplify the construction. Here, we suggest a new method for quantum simulation in circuit QED, that provides versatility in model design and complete control over its parameters with minimal hardware requirements. We show how these features manifest through examples of quantum simulation of Dirac dynamics, which is relevant to the study of both high-energy physics and 2D materials. We conclude by discussing the advantages and limitations of the proposed method.

Precise evaluation of the isotope shift (IS) factors for seven low-lying potassium states is achieved using relativistic coupled-cluster theory. The energies of these states are compared with the experimental data to confirm the accuracy of wave functions calculated at different approximations and to highlight the significance of many-body and relativistic effects. Various methods are used to compute the IS factors, with the finite-field (FF) approach yielding results that align with observed and semiempirical data. This is attributed to orbital relaxation effects that are present naturally in the FF method but emerge only through perturbation in other methods. Using results from the FF approach, we review the mean-square-radius difference between ${}^{38m}\mathrm{K}$ and $^{39}\mathrm{K}$, which is combined with muonic atom x-ray spectroscopy and updated calculation of the nuclear polarizability effect to deduce the absolute radius of ${}^{38m}\mathrm{K}$. Finally, we evaluate the isospin symmetry breaking (ISB) in the isotriplet by integrating the radius of ${}^{38m}\mathrm{K}$ with an updated radius of $^{38}\mathrm{Ca}$, concluding that the ISB is compatible with zero. This finding offers a stringent benchmark for nuclear models of ISB corrections in nuclear beta decay, which play a key role in determining the ${V}_{ud}$ matrix element.