Physical Review A

The authors present their Perspective on using atomic vapors for “practical” quantum sensors—defined here as sensors that have been stripped to their bare essentials, made compact and inexpensive, and designed for use by non-specialists in uncontrolled environments, all while retaining as much as possible of their ideal performance. They discuss the basic physics, techniques, and tools in common use, as well as a recommended process for producing a practical sensor.

While disordered two-dimensional systems are generally expected to exhibit Anderson localization of all wave excitations, the authors predict that light scattered by two-level atoms in a thin planar waveguide should undergo a genuine localization-delocalization transition as the atomic density is increased. The transition is driven by near-field dipole-dipole interactions between atoms.

Standard effective Hamiltonians for light-matter interactions rely on approximations that break down at high laser intensity. The authors show that these limitations can be overcome, in a computationally efficient way, by using quasidegenerate Rayleigh-Schrödinger perturbation theory.

The authors measure the magic wavelength of the potassium-40 $D_1$ transition, at which the ground and excited states experience identical trapping potentials. The measurement is done by tracking the light shift of atoms held in a wavelength-tunable optical tweezer. The result, 1227.54 nanometers, agrees with relativistic all-order calculations and enables shift-free optical addressing of fermionic potassium in tweezer arrays.

The authors discover a “fish-fin”-like structure in terahertz-assisted high-order harmonic generation. A saturation energy of $8U_p$ is found for long electron excursions spanning multiple optical cycles using a weak-to-moderate, laboratory-scale THz field and is shown to persist under macroscopic propagation.

Wigner’s friend thought experiments have long challenged whether measurement outcomes can be absolute; here, the author examines whether even the “free choices” observers make in setting up an experiment can be absolute. By combining the Wigner’s friend scenario with the Pusey–Barrett–Rudolph theorem on the reality of the quantum state, the author derives a no-go result suggesting that any resolution to extended Wigner’s friend paradoxes that abandons absoluteness must also incorporate a relational nature for free choices.

The authors systematically map the four-dimensional parameter space of double microwave shielding using universal dimensionless calculations to identify operating regimes free of field-linked bound states. By incorporating realistic experimental field constraints, they demonstrate that heavy, strongly dipolar molecules achieve strong two-body loss suppression alongside broad tunability of effective dipolar interactions.

The authors present a combined theoretical and experimental advance showing that $d$+1 projective measurement bases suffice for complete quantum-state tomography in any finite dimension, without relying on mutually unbiased bases. They demonstrate the scheme on a silicon photonic chip, achieving fidelities above 0.96.

Because ideal Gottesman-Kitaev-Preskill (GKP) states are invariant under stabilizers, researchers often assume that measuring a state’s stabilizers directly quantifies its closeness to an ideal GKP state. In fact, the author shows that high stabilizer expectation values only provide an upper bound on proximity, and that states far from an ideal GKP state can still yield excellent stabilizer expectation values.

The authors develop an instantaneous-mode description for dispersive laser cavities by exploiting the separation of timescales between fast cavity fields and slow carrier dynamics. By deriving low-dimensional rate equations parametrized directly by the effective mirror reflectivity, the approach accurately reproduces full-model self-pulsing dynamics in Fano lasers and simplifies the stability analysis of dispersive instabilities.

The authors show how quantum coherence fluctuations of light can serve as a degree of freedom for squeezing. They demonstrate that squeezing these fluctuations leads to squeezing of the magnitude and/or position of interference fringes for both bright and single-photon light.

The authors reveal that the electric field can induce a well in the potential energy surface between two ultracold alkali-metal polar molecules in nonadjacent rotational states. The potential well is deep enough to support field-linked tetratomic states within experimentally achievable field strengths, and the elastic cross section between molecules becomes highly tunable due to the emergence of these tetratomic states.

The authors realize a new dipolar mixture of Bose-Einstein condensates of Dy isotopes. The mixture features a broad interspecies Feshbach resonance, which allows the authors to control a miscible-immiscible transition in the binary mixture.

Quantum batteries need precision-focused charging protocols to provide reliable quantum advantage. The authors borrow a technique from quantum thermodynamics to demonstrate that a sequential multi-qubit quantum battery can be charged with high precision, even in the presence of non-idealized working conditions, by exploiting specific quantum states of light.

A universal method for block encoding the Liouville representation of quantum channels is presented, enabling the manipulation of the spectrum of unknown quantum channels.

The authors report calculations of the EUV emission spectrum of Sn${}^{12+}$ with complete configuration interaction within the $n=4$ shell and core-valence correlation. Their approach places the dominant emission feature at the experimental wavelength of 13.5 nm without any empirical fitting.

The authors reveal a fractional power-law decay in the spontaneous emission of a two-level system in the short- and long-time regimes. The fractional exponent is determined by the dispersion relation and spatial dimension of the environment.

The authors propose a femtosecond chiroptical switch in atomic hydrogen that maps the otherwise unobservable global phase of a Rabi‑oscillating system onto the chirality of a bound electron wave packet. They demonstrate that this global phase is dominated by a geometric phase accumulated during cyclic evolution on the Bloch sphere, which endows the switch with high robustness against variations in the control‑pulse area.

The authors demonstrate that the winding number of a toroidal Bose-Einstein condensate can be deterministically and robustly engineered by manipulating the motion of dark solitons via nonlinear coupling with the localized waves driven by external forces. The increment or decrement of the winding number is determined by the direction in which the soliton velocity crosses zero, and accelerating multiple dark solitons enables versatile tailoring of the winding number.

The authors calculate correlations between Hawking radiation, its partner wave inside the horizon, and greybody factors near an acoustic horizon in a driven-dissipative fluid of light. Resolving the correlations in the frequency domain allows one to weigh the contributions of each pair to the total output quantum state

Chiral arrangements of cold atoms can exhibit a strong collective chiroptical response mediated entirely by electric-dipole interactions, providing a route to probe chirality without relying on weak magnetic-dipole transitions. The response is tunable through probe detuning and strongly enhanced in the subwavelength regime, where it is associated with the formation of subradiant collective modes.

The authors establish a relation between the conservation of coherence and the conservation of energy. They analyze partially coherent fields in the focal region of a converging lens, and show topological differences between the coherence flux and the energy flux.

The authors extend analytical derivations for expectation value distributions to random mixed quantum states and general measurement operator sets, using a combinatorics framework to calculate their moments. Using simulated noisy brickwork circuits, they introduce an effective global depolarizing model that accounts for empirical peak behaviors and reveal that non-symmetric measurement sets yield distinct multimodal distributions.

The authors calculate quantum memory efficiency in a cavity-coupled ensemble of spins by examining absorption and emission efficiency. Based on this they design a method for storage and retrieval that involves modulating the coupling strength between the cavity and the ensemble.

The combination of a static, topologically trivial optical lattice with a moving nonlinear lattice enables quantized soliton transport. In the topological regime, the soliton displacement can be predicted beforehand from the Chern number of the effective Hamiltonian.

The authors develop an analytical theory for the complex subradiant eigenvalues of a finite one-dimensional emitter array coupled to an ideal or nonideal waveguide. They demonstrate that while Bragg-edge destructive interference drives an $N^{-3}$ linewidth scaling with deep-subwavelength parity oscillations, near-field dipole-dipole interactions dominate the collective energy shift, which exhibits a distinct $N^{-2}$ finite-size correction.