Atomic and Molecular Physics

Atomic and molecular physics addresses the structure and interactions of atoms and molecules, uniting quantum theory with experimental observation to explain phenomena from spectral lines to collision dynamics. Atoms, composed of a dense, positively charged nucleus surrounded by orbiting electrons, exhibit discrete energy levels that govern emission and absorption spectra. Quantum mechanics replaces classical orbits with wave-functions whose square magnitudes yield probabilities of electron position, and whose boundary conditions define quantised angular momenta and spins. Molecules introduce additional complexity through vibrational and rotational states, intermolecular forces and transition pathways. Together, atomic and molecular theories underpin our understanding of plasmas, astrophysical media, chemical reaction rates, spectroscopy and emerging applications in quantum technologies. Advances in precision measurement, computational methods and ultrafast probing continue to reveal subtle effects in Rydberg interactions, electron scattering, quantum defect structures and non-radiative decay mechanisms.

Research from Nature Portfolio

High-fidelity entangling gates have been demonstrated on arrays of up to sixty neutral atoms excited to Rydberg levels, achieving two-qubit gate fidelities of 99.5 percent in parallel. The experiment employs optimal single-pulse excitation and engineered atomic dark states to suppress photon scattering, surpassing thresholds for surface-code quantum error correction and enabling scalable multi-qubit operations under realistic conditions. A complementary study revealed a quantum processor architecture in which entangled atoms are coherently transported across layers of single- and two-qubit operations by optical tweezers. Dynamic, reconfigurable connectivity permitted programmable generation of graph and surface-code states, hybrid analog–digital simulations and direct measurement of many-body entanglement dynamics. Further progress in Floquet-frequency modulation has broken the conventional Rydberg-blockade radius limit, extending the range of coherent interactions and unlocking new connectivity regimes for quantum simulation and computation.

Research from all publishers

Complete cross-section data for electron scattering from 1-methyl-5-nitroimidazole were obtained by combining low-energy multichannel variational calculations with high-energy independent-atom models. The resulting elastic, inelastic and ionisation cross sections support detailed simulations of electron transport through radiosensitiser molecules in plasma and biological environments. In a separate theoretical investigation, relativistic partial-wave analyses with complex optical potentials yielded differential, momentum-transfer and total cross sections for electron and positron collisions with ethane from 1 eV to 1 MeV, including the first predictions of spin-polarisation observables. These results expose screening effects at forward angles and highlight differences between electron and positron scattering. On the quantum defect front, a new Python library—mqdtfit—implements empirical multichannel quantum defect theory calculations. It fits experimental Rydberg series to eigenchannel- and reactance-matrix parametrisations, computes channel mixing coefficients and generates Lu–Fano plots, greatly simplifying the analysis of complex perturbed spectra in multielectron atoms.

Atomic and Molecular Physics publication trend

The graph below shows the total number of articles in atomic and molecular physics across all publications each year (not limited to Nature Index journals).

Technical terms

Rydberg blockade: The inhibition of simultaneous Rydberg excitation within a characteristic radius due to strong dipole interactions, enabling controlled multi-atom logic operations.

Surface-code threshold: The minimum gate fidelity required for fault-tolerant error correction in a surface-code architecture.

Independent atom model (IAM): A scattering approximation that treats molecules as collections of isolated atoms, later corrected for interatomic screening effects.

Multichannel quantum defect theory (MQDT): A framework that parameterises deviations of Rydberg series from hydrogenic energies through channel-coupling matrices and effective quantum defects.

Lu–Fano plot: A graphical representation of quantum defects versus energy that reveals channel mixing and perturber states in Rydberg spectra.

Electron scattering cross section: A measure of the probability of a specified collision process, such as elastic, inelastic or ionising scattering, expressed as an effective area.

References

1. High-fidelity parallel entangling gates on a neutral-atom quantum computer. Nature (2023).
2. A quantum processor based on coherent transport of entangled atom arrays. Nature (2022).
3. Floquet-tailored Rydberg interactions. Nature Communications (2023).
4. Electron Scattering from 1-Methyl-5-Nitroimidazole: Cross-Sections for Modeling Electron Transport through Potential Radiosensitizers. International Journal of Molecular Sciences (2023).
5. Scattering of e± by C2H6 Molecule over a Wide Range of Energy: A Theoretical Investigation. Molecules (2023).
6. mqdtfit: A collection of Python functions for empirical multichannel quantum defect calculations. Computer Physics Communications (2024).