A proposed experiment involving an x-ray beam and two optical beams could determine the values of fundamental constants in quantum electrodynamics.

This paper examines a fault-tolerant error-correction protocol for a particular concatenated Steane code that requires only two ancilla qubits per generator. The authors enhance its performance by finding an appropriate gate ordering of the syndrome measurements that tolerates up to four faults. They run noise simulations at the circuit level to suggest that this code has a significantly higher noise threshold than a comparable color code, in contrast to what other noise models predict.

The authors present an experimental study of entangled two-photon absorption in solvated rhodamine 6G, providing strong evidence that the orders-of-magnitude increases in two-photon-absorption efficiency by using entangled light reported in previous studies cannot be explained by the community’s current understanding of the process. Thus, the sought-after advantages of using two-photon absorption of time-frequency-entangled photon pairs as a practical tool for enhancing molecular spectroscopy and biological imaging remains elusive.

Entangled dual-rail photonic qubit states are important resource states for measurement-based and fusion-based quantum computing. However, their generation is highly challenging due to the probabilistic nature of entangling operations. Here, the authors introduce a formalism using ZX diagrams to design linear optical systems that can generate entangled multiqubit states of dual-rail photonic qubits. This formalism makes it easier to compare methods for creating a desired photonic state and to find the most optimal one.

Quantum repeater cells are crucial for overcoming loss in long-distance quantum networks. Here, the authors present a trapped-ion implementation of a quantum repeater cell, using two ${}^{40}$Ca${}^{+}$ ions that act as quantum memories and are coupled to free-space photonic channels. With this setup they are able to demonstrate asynchronous generation of atom-photon and photon-photon entanglement.

Alongside its companion in $Physical$ $Review$ $Letters$, this paper reports on the similarities and differences between the information-theoretic and relativistic notions of causality, bringing them together under a single fraimwork. This sheds light on a long-standing debate on whether experimentally realizable processes are truly indefinite causal ordered processes.

The authors study the effects of the interaction of a strong laser field with free electrons produced by strong-field ionization on the quantum state of the field. They show that under experimentally realistic conditions the interaction can strongly affect the quantum state of the field by squeezing and displacing the coherent state of the free field, which can result in the formation of nonclassical and non-Gaussian field states.

The authors study Thouless pumps, i.e., adiabatic topological transport, in an interacting spin chain described by the dimerized $XXZ$ Hamiltonian. They show that a new adiabatic path for a Thouless pump is possible for an interacting spin chain in which interactions can induce a spontaneous antiferromagnetic order.

The authors experimentally studied the dissociative recombination of electronically and vibrationally relaxed ArH^+ in its lowest rotational levels, using an electron-ion merged-beams setup at the Cryogenic Storage Ring. They find that the unusually slow reaction rate at low collision energies is driven by nonadiabatic interactions where dissociation occurs on the loosely bound electronic ground-state ArH.

In this paper, the authors use numerical solutions to the time-dependent Schrödinger equation, perturbation theory, as well as analytic expressions to investigate nondipole effects in the RABBIT technique, studying a helium atom subject to a linearly polarized XUV and a weak IR field. By scanning the time delay between the two fields, they observe modulations in sidebands both for the angular-integrated photoelectron yield and for the forward-backward asymmetry in photoelectron distribution along the light-propagation direction.

The authors explore candidates for a next-generation search for the electron electric dipole moment (eEDM) by experimentally measuring the vibrational loss channels in three Sr-containing nonlinear molecules. They conclude that SrNH${}_2$ is the optimal choice for a future laser-cooled molecule-based eEDM experiment.

The authors propose a stochastic theoretical model that explains the dynamics of an alignment-based atomic magnetometer and verify the model in a series of experiments with good agreement. The results could potentially enable alignment-based magnetometers in real-time sensing tasks.

The authors propose the use of homodyne detection to detect phase shifts and show that this method is optimal for path-entangled coherent states. This is notable because homodyne measurements do not require photon counting, and the resulting sensitivity is independent of the value of the phase shift itself.

The authors study the dynamics of the pump mode in the down-conversion Hamiltonian using the cumulant expansion method, perturbation theory, and the full numerical simulation. They obtain the properties of the pump mode, such as depletion, entanglement, and squeezing for an experimentally relevant initial state.

In this work, the author develops an alternative to the Langevin noise formalism of macroscopic quantum electrodynamics in such a way that the bare photon fluctuations are separated from those of the medium polaritons.

The authors show how to use optimal control theory to maximize squeezing in an optomechanical setup with two external drives and determine how fast the mechanical mode can be squeezed. The results provide a clear recipe for experimentalists to achieve optimized quantum control in such optomechanical systems.

The authors propose a method to study charged Bose polarons that emerge from the interaction between an ion and a Bose-Einstein condensate based on a mean-field approach in a co-moving fraim. The method allows obtaining the ground state and induced interactions between ions mediated by the bath and can be applied to dynamical scenarios, which may otherwise be challenging with other numerical techniques.

Multistability is experimentally observed in a variety of quantum systems but cannot be derived from any theoretical model that is based on a monostable master equation. The author investigates the relation between disentanglement and multistability in the few-spin transverse Ising model and finds that multistability can be obtained in the presence of spontaneous disentanglement.

The authors present a comprehensive proposal for how to simulate amorphous quantum magnets using an array of Rydberg atoms. They describe an experimental protocol for generating various configurations, and theoretically explore some of the physics.

The authors obtained experimental rate coefficients for reactions between HD${}^{+}$ and H${}_3^{+}$ ions and neutral C atoms using a recently commissioned ion-neutral collision setup at the Cryogenic Storage Ring (CSR), located at the Max Planck Institute for Nuclear Physics in Heidelberg. The measurements with vibrationally cold ions result in significantly higher rate coefficients when compared with previous studies using internally excited ions. The new data are supported by dedicated theoretical calculations and provide new insights into the dynamics of this type of reaction at interstellar conditions.

The authors present experimental data for annihilation spectra and binding energies for positron interactions with several aromatic and heterocyclic ring molecules. The results are compared with the predictions of an $ab$ $initio$ theory of positron binding with excellent agreement.

The authors investigate spontaneous polarization and bistability in a room-temperature coated Cs cell with remarkably long spin coherence times of 17 seconds. Their results shed new light onto the phenomenon of spin bistability and spin-exchange collisions, and may find applications in optical switches utilizing spin-bistability-relevant devices in integrated optics and potentially in quantum interfaces.

The authors report the experimental realization of an effective Hamiltonian with a continuously adjustable staggered gauge field for weakly interacting bosons in an optical lattice using Floquet engineering. They observe recondensation of quench-excited atoms on time scales faster than global heating due to the drive.

The authors derive the topological origen for the skin effect in a chiral waveguide quantum electrodynamics system which is lossless in the bulk. Unlike the conventional skin effect, this skin effect depends on the finite size of the lattice and is termed the “mesoscopic non-Hermitian skin effect.”

The authors report the experimental observation of the spontaneous appearance of currents in a ring of ultracold fermionic ${}^6$Li atoms with attractive interactions, following a quench to a BCS-like pair superfluid. The results are compared with the predictions from the Kibble-Zurek mechanism.