arXiv subjects

H. R. Sadeghpour

Publications and source records attributed to H. R. Sadeghpour.

At least 19 recordsLinked to original sources

arXiv2026

A Protocol for Shielding-Enhanced Loading of Single Polar Molecules into Optical Tweezers

We propose the high-fidelity preparation of single bosonic molecules in optical tweezers starting from small tweezer-trapped molecular ensembles. Our scheme combines a static electric field and a microwave field to generate strong, tunable, anisotropic interactions that shield the molecules against two-body collisional loss. We show that this shielding eliminates all long-range bound states, preventing three-body recombination. This elimination persists for all microwave ellipticities, including the experimentally practical limit of linear polarization. Application of an additional electric field gradient can be used to induce controlled spilling of strongly interacting molecules out of the trap until one remains. With realistic experimental parameters, we estimate that single tweezer-trapped NaCs molecules can be isolated from a pair with fidelities exceeding 99\%, and $> 95\%$ per site across an array. These results establish collisional shielding with electric fields as an effective tool for preparing highly-filled tweezer arrays of polar molecules.

physics.atom-ph↗

arXiv2026

First-order phase transition in atom-molecule quantum degenerate mixtures with coherent three-body recombination

We map the phase diagram of a two-mode atom-molecule Bose-Einstein condensate with Fano-Feshbach and coherent three-body recombination (cTBR) terms. The standard second order phase transition observed as the molecular energy is tuned through the Feshbach resonance, is replaced by a first order transition when cTBR becomes prominent, due to a double-well structure in the free energy landscape. This transition is associated with atom-molecule entanglement, bistability, and molecular metastability. Our results establish cTBR as a powerful knob for quantum state engineering and control of reaction dynamics in ultracold chemistry.

cond-mat.quant-gas↗

arXiv2026

Catalytic formation of H_2 on carbonaceous dust grains - implications for interstellar observations

We use kinetic Monte Carlo (KMC) simulations to study molecular hydrogen formation on carbonaceous dust grain surfaces, validated against recent laboratory measurements of H$_2$ formation on coronene films at temperatures from 10 to 250 K. The model uses a three-dimensional amorphous carbon lattice with heterogeneous physisorption ($45 \pm 5$ meV) and chemisorption ($1.75 \pm 0.25$ eV) sites, and tracks both Langmuir--Hinshelwood (LH) and Eley--Rideal (ER) formation channels within a stochastic Gillespie event-driven framework. The model reproduces the measured efficiency curve within the experimental uncertainties, including the isothermal (constant surface temperature) measurements at 100 - 250 K. The simulations correctly describe the phase boundary between the LH and ER driven processes as functions of grain temperature and the observed crossover. Under interstellar medium conditions, 10 - 250 K and n = 10 - 10$^4$ cm$^3$, the model predicts three distinct regimes for the formation efficiency $ε$, the fraction of impinging H atoms released as H$_2$. At 10 K diffusion is slow and $ε\approx 0.06$. Between 20 K and 80 K, LH dominates and $ε\approx 0.28$. Above 150 K, an ER plateau at $ε= 0.19$ is sustained by chemisorption-trapped H atoms. The LH-to-ER crossover occurs between 100 and 120 K. At 100 K we observe a 16\% density-dependent stochastic enhancement, which rate-equation models cannot capture. At T$_{dust}$ = 60 K, n = 10$^3$ cm$^3$ we find the ratio of H$_2$ formation to free-fall time $t_{{\rm H}_2}/t_{\rm ff} \approx 0.93$, so dust-catalysed H$_2$ chemistry can keep pace with gravitational collapse in high-redshift star-forming environments.

astro-ph.GA↗

arXiv2026

Imaginary time evolution and ground state preparation using unitary multi-copy protocols

Efficient low-energy state preparation is a key objective in quantum computation and quantum simulation. Quantum imaginary-time evolution replaces real-time dynamics with imaginary-time dynamics, exponentially suppressing higher-energy eigenstates. We introduce deterministic unitary protocols that approximate imaginary-time evolution for ground state preparation. The protocols require multiple copies of the system, real-time evolution under the system Hamiltonian, and controlled-SWAP operations (or more general SWAP-generated unitaries). Our analysis focuses on two concrete circuit families: a tree architecture with provable polynomial-in-depth convergence but rapidly growing width, and a compact "hedge" architecture that achieves comparable accuracy with only polynomial width in a heuristic construction supported by numerics. Numerical evidence indicates that mid-circuit post-selection can accelerate convergence with practical success probabilities. Separately, we demonstrate that circuit volume can be traded for the shot complexity of post-circuit observable estimation in the ground state preparation setting. Finally, we outline concrete platform-specific implementations in which multi-copy registers and SWAP-mediated couplings are natural, illustrating how these hybrid analog-digital circuits can complement existing state-preparation methods in the near term.

quant-ph↗

arXiv2026

Cavity-Mediated Collective Resonant Suppression of Local Molecular Vibrations

Recent advances in polaritonic chemistry suggest that chemical reactions can be controlled via collective vibrational strong coupling (VSC) in a cavity. In this fully analytical work, we demonstrate that the collective vibrations of a molecular ensemble under VSC execute a beating with a period inversely proportional to the collective vacuum Rabi splitting. Significantly, this collective beating is imprinted on the local dynamics and resonantly suppresses individual molecular vibrations when a fraction of molecules are vibrationally excited, as in activated complexes formed in chemical reactions. This emergent beating occurs on significantly longer time scales than the individual molecular vibration or the cavity field oscillation period, peaking at the cavity-molecule resonance, consistent with polaritonic chemistry experiments. The cavity mediates an energy exchange between excited and ground-state molecules, affecting the dynamics of the entire ensemble. These findings suggest that the dynamics in polaritonic chemical reactions may not be in full equilibrium. In the ultra-strong coupling regime, we find that the local vibrations are modified by the cavity even at short time scales. Notably, these dynamical effects also extend to isotropic molecular ensembles in our model. Our analytical model offers insights into how collective VSC can dampen local molecular vibrations at resonance, potentially altering chemical reactivity.

quant-ph↗

arXiv2026

Noise-enhanced Ballistic Expansion of Polariton Wave-packets in a Multimode Cavity

Advances in optical measurements enable precise tracking of cavity polariton wave-packets across broad spatial and temporal ranges, but how dephasing reshapes their real-space dynamics over multiple time scales remains unclear. Here we show, using a stochastic multimode Tavis-Cummings model, that dephasing noise leads to a robust hierarchy of dynamical regimes comprising Rabi oscillation damping, center-of-mass slowdown, population relaxation, and ballistic-to-diffusive crossover, in the order of increasing time scales. We further predict that dephasing can enhance ballistic spreading and sustain it far beyond the microscopic dephasing time by two orders of magnitude. These predictions agree with recent microscopy measurements and provide experimentally testable guidance for engineering energy transport in polaritonic platforms.

physics.optics↗

arXiv2026

Observation of resonant monopole-dipole energy transfer between Rydberg atoms and polar molecules

Resonant energy transfer (RET), between equal parity 1s65s$^3\mathrm{S}_1$ and 1s66s$^3\mathrm{S}_1$ Rydberg levels in helium has been observed in low-temperature ($\sim80$ mK) collisions with ammonia molecules which undergo inversion transitions in their X$^1$A$_1$ ground electronic state. This hybrid Rydberg-atom-polar-molecule RET represents a monopole-dipole energy exchange reaction that necessarily requires spatial overlap of the Rydberg-electron and molecular wavefunctions. Calculations, that account explicitly for the charge-dipole interaction between the Rydberg electron and the molecule, provide a quantitative explanation of the observations. Total parity is conserved in the reaction through the mixing of collisional angular momentum in the atom-molecule complex. This work opens opportunities to expand the toolbox for quantum science with charge-dipole-mediated energy exchange in hybrid neutral-atom-polar-molecule platforms.

physics.atom-ph↗

arXiv2026

Signatures of rigidity and second sound in dipolar supersolids

We propose a dynamical protocol to probe the rigidity and phase coherence of dipolar supersolids by merging initially separated fragments in quasi-one-dimensional (1D) double-well potentials. Simulations based on the extended Gross-Pitaevskii equation reveal distinct dynamical signatures across phases. Supersolids exhibit damped crystal oscillations following barrier removal, with the damping rate reflecting superfluid connectivity. A phase-imprinted jump additionally triggers metastable dark solitons, which excites second sound, as revealed by an out-of-phase drift between the droplet lattice and the superfluid background. Our results show a realizable path to dynamically detect the second sound and rigidity of supersolids, as well as to realize and probe soliton formation.

cond-mat.quant-gas↗

arXiv2026

Reconfigurable Four-Photon Interference among Three Nodes on a Field Deployed Metropolitan Fiber Network

Advanced quantum networking protocols beyond bi-photon, point-to-point links rely critically on the ability to perform multi-photon interference across multiple nodes under realistic operating conditions. Yet experimental validation of such higher-order, multi-node interference effects in deployed metropolitan fiber networks remains limited. Here, we report a field demonstration of polarization-controlled reconfigurable four-photon interference over three distant nodes on a deployed metropolitan fiber network. Using a fully fiber-coupled linear-optical platform, we observe a fusion-type four-photon interference signature in presence of real-world impairments, including photon loss, polarization drift, and timing uncertainty. By performing polarization-resolved measurements on two locally retained photons, we conditionally select distinct two-photon coincidence channels that exhibit Bell-like and N00N-like behavior. Rather than pursuing multi-partite entanglement verification, this work focuses on establishing the technical feasibility of multi-photon, multi-node interference and reconfigurable conditional state preparation in the field in a deployed fiber network environment. These results serve as a systems-level validation toward future multi-photon, multi-node quantum networking architectures that require robust interference performance outside the laboratory.

quant-ph↗

arXiv2025

Observation of spin singlet butterfly Rydberg molecules in an ultracold atomic Rb gas

We report the observation of spin-singlet ultra-long range Rydberg butterfly molecules consisting of a ground-state atom bound to a Rydberg atom by $P$-wave scattering of $^{87}$Rb Rydberg electrons from $^{87}$Rb(5s) atoms. A three-photon excitation scheme enables the photoassociation of these molecules by weakly admixing Rb($18f_{7/2}$) states. The measured binding energies, kilo-Debye permanent electric dipole moments, and lifetimes are in excellent agreement with theory. Two long-lived vibrational levels, red detuned from the Rb($18f_{7/2}$) threshold, are observed. This experiment is a foundational step in the production of ultra-cold anions and heavy Rydberg ion-pair systems.

physics.atom-ph↗

arXiv2025

Anisotropic and non-additive interactions of a Rydberg impurity in a quantum bath

We present a framework for treating anisotropic and non-additive impurity-bath interactions - features that are ubiquitous in realistic quantum impurity problems, but are often neglected in conventional approaches relying on additive, spherically symmetric pseudopotentials. To illustrate this, we focus on a Rydberg atom immersed in a Bose-Einstein condensate, where the internal-state degeneracy of the Rydberg impurity gives rise to configuration-dependent non-additive potentials. With increasing interaction strength, anisotropy-induced partial-wave mixing generates distinct polaron and molaron resonances, allowing for radially and angularly excited bound states to become accessible. This approach captures the anisotropy and non-additivity characteristic of a Rydberg impurity immersed in a quantum bath, and provides broad applicability to a host of quantum impurity problems beyond the Fröhlich paradigm.

cond-mat.quant-gas↗

arXiv2025

Precision measurement of Cs($nF_J$) quantum defects and calculations of scalar and tensor polarizabilities of the $nS_{1/2}$, $nP_J$ ,$nD_J$ , and $nF_J$ series

In this paper, we extend our recent work on cesium S and D states [Phys. Rev. Lett. 133, 233005 (2024)] to the F states. We present absolute frequency measurements of the $|6S_{1/2}, F = 3\rangle \rightarrow nF_{5/2,7/2}(n = 28-68)$ Rydberg series to measure the spectrum of $^{133}$Cs. Atomic spectra are obtained using a three-photon excitation scheme referenced to an optical frequency comb in a sample of ultracold $^{133}$Cs. By globally fitting the absolute-frequency measurements to the modified Ritz formula, we determine the quantum defects of the $nF_{5/2}$ and $nF_{7/2}$ series. The ionization potential extracted for both series from the modified Ritz formula agrees with our measurements based on the S and D series. Fine-structure intervals are calculated and parameterized. The wave functions computed for the energies from the quantum defects are used to calculate transition dipole moments. We compare the reduced electric-dipole matrix elements with available benchmarks and find agreement within the precision of those works. The scalar and tensor polarizabilities of the $nS_{1/2}$, $nP_J$ , $nD_J$ and $nF_J$ series are calculated based on the now more accurate set of wave functions. Moreover, we report the polarizability as a series in powers of the effective principal quantum number and find the main coefficients of the expansion. The results will be useful for calculating properties of $^{133}$Cs such as collision and decay rates, polarizabilities, and magic wavelengths.

physics.atom-ph↗

arXiv2025

Tunable pairing with local spin-dependent Rydberg molecule potentials in an atomic Fermi superfluid

We explore the energy spectrum and eigenstates of two-component atomic Fermi superfluids with tunable pairing interactions in the presence of spin-dependent ultra long-range Rydberg molecule (ULRM) potentials, within the Bogoliubov-de Gennes formalism. The attractive ULRM potentials lead to local density accumulation, while their difference results in a local polarization potential and induces the in-gap Yu-Shiba-Rusinov (YSR) states whose energies lie below the bulk energy gap. A transition from equal-population to population-imbalance occurs as the pairing strength falls below a critical value, accompanied by the emergence of local Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like states characterized by out-of-phase wave functions and lower energies compared to the YSR states. The negative contribution emanating from the FFLO-like states also causes a sign change in the gap function within the ULRM potentials. Depending on the Rydberg state generating the ULRM potentials, the transition towards population-imbalance can be on either the BCS or the Bose-Einstein condensation side of the Fermi superfluid. Additionally, spin-polarized bound states arise along with oscillatory ``clumpy states" to compensate for the local density difference. Finally, we discuss possible experimental realizations and measurements of the composite Rydberg atom-Fermi superfluid system.

cond-mat.quant-gas↗

arXiv2025

Competition of light- and phonon-dressing in microwave-dressed Bose polarons

We theoretically investigate the stationary properties of a spin-1/2 impurity immersed in a one-dimensional confined Bose gas. In particular, we consider coherently coupled spin states with an external field, where only one spin component interacts with the bath, enabling light dressing of the impurity and spin-dependent bath-impurity interactions. Through detailed comparisons with ab-initio many-body simulations, we demonstrate that the composite system is accurately described by a simplified effective Hamiltonian. The latter builds upon previously developed effective potential approaches in the absence of light dressing. It can be used to extract the impurity energy, residue, effective mass, and anharmonicity induced by the phononic dressing. Light-dressing is shown to increase the polaron residue, undressing the impurity from phononic excitations because of strong spin coupling. For strong repulsions-previously shown to trigger dynamical Bose polaron decay (a phenomenon called temporal orthogonality catastrophe), it is explained that strong light-dressing stabilizes a repulsive polaron-dressed state. Our results establish the effective Hamiltonian framework as a powerful tool for exploring strongly interacting polaronic systems and corroborating forthcoming experimental realizations.

cond-mat.quant-gas↗

arXiv2025

Universality class of a spinor Bose-Einstein condensate far from equilibrium

Scale invariance and self-similarity in physics provide a unified framework to classify phases of matter and dynamical properties near equilibrium in both classical and quantum systems. This paradigm has been further extended to isolated many-body quantum systems driven far from equilibrium, where physical observables exhibit dynamical scaling with universal scaling exponents. Universal dynamics appear in a wide range of scenarios, including cosmology, quark-gluon matter, ultracold atoms, and quantum spin magnets. However, how universal dynamics depend on the symmetry of the underlying Hamiltonian in nonequilibrium systems remain an outstanding challenge. Here, we report on the classification of universal coarsening dynamics in a quenched two-dimensional ferromagnetic spinor Bose gas. We observe spatiotemporal scaling of spin correlation functions with distinguishable scaling exponents that characterize binary and diffusive fluids. The universality class of the coarsening dynamics is determined by the symmetry of the order parameter and the dynamics of the topological defects, such as domain walls and vortices. Our results provide a categorization of the universality classes of far from equilibrium quantum dynamics based on symmetry properties of the system.

cond-mat.quant-gas↗

arXiv2024

Ultra precise determination of Cs($nS_{1/2}$) and Cs($nD_J$) quantum defects for sensing and computing: Evaluation of core contributions

We make absolute frequency measurements of Cs Rydberg transitions, $\vert 6S_{1/2}, F=3 \rangle \rightarrow \vert nS_{1/2}~(n=23\rm{-}90)\rangle$ and $\vert nD_{3/2,5/2}~(n=21\rm{-}90)\rangle$, with an accuracy of less than $ 72\,\rm kHz$. The quantum defect parameters for the measured Rydberg series are the most precise obtained to date. The quantum defect series is terminated at $δ_4$, showing that prior fits requiring higher order quantum defects reflect uncertainties in the observations. The precision of the measured quantum defects allow for the calculation of Rydberg electric-dipole transitions and fine-structure intervals extrapolated from high principal quantum numbers, to rival that of sophisticated many-body relativistic calculations carried out at low Rydberg principal quantum numbers. We quantitatively predict the contributions to the quantum defect parameters from core polarization and core penetration of Cs inner shell electrons. A new value for the ionization energy, consistent across the $ nS_{1/2}$ and $ nD_{3/2,5/2}$ Rydberg series, is reported at $31406.467 751 48 (14)~\rm{cm}^{-1}$.

physics.atom-ph↗

arXiv2024

Dynamical generation and transfer of nonclassical states in strongly interacting light-matter systems in cavities

We propose leveraging strong and ultrastrong light-matter coupling to efficiently generate and exchange nonclassical light and quantum matter states. Two initial conditions are considered: (a) a displaced quadrature-squeezed matter state, and (b) a coherent state in a cavity. In both scenarios, polaritons mediate the dynamical generation and transfer of nonclassical states between light and matter. By monitoring the dynamics of both subsystems, we uncover the emergence of beatings in the collective matter oscillations. The beating period depends on the particle density through the vacuum Rabi splitting and peaks sharply under light-matter resonance conditions. For initial condition (a), nonclassicality is efficiently transferred from matter to photons under strong and ultrastrong coupling. However, for initial condition (b), nonclassical photonic states are generated only in the ultrastrong coupling regime due to the counter-rotating terms, highlighting the advantages of ultrastrong coupling. Furthermore, in the ultrastrong coupling regime, distinctive asymmetries relative to cavity detuning emerge in dynamical observables of both light and matter. The nonclassical photons can be extracted through a semi-transparent cavity mirror, while nonclassical matter states can be detected via time-resolved spectroscopy. This work highlights that hybrid polariton states can be utilized for dynamically generating nonclassical states, with potential applications in quantum state transfer.

quant-ph↗

arXiv2024

Tunneling dynamics of $^{164}$Dy supersolids and droplets

The tunneling dynamics of a magnetic $^{164}$Dy quantum gas in an elongated or pancake skewed double-well trap is investigated with a time-dependent extended Gross-Pitaevskii approach. Upon lifting the energy offset, different tunneling regimes can be identified. In the elongated trap and for sufficiently large offset, the different configurations exhibit collective macroscopic tunneling. For smaller offset, partial reflection from and transmission through the barrier lead to density accumulation in both wells, and eventually to tunneling-locking. One can also reach the macroscopic self-trapping regime for increasing relative dipolar interaction strength, while tunneling vanishes for large barrier heights. A richer dynamical behavior is observed for the pancake-like trap. For instance, the supersolid maintains its shape, while the superfluid density gets distorted signifying the emergence of peculiar excitation patterns in the macroscopic tunneling regime. The findings reported here may offer new ways to probe distinctive dynamical features in the supersolid and droplet regimes.

cond-mat.quant-gas↗