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The ability to slow down light at the single-photon level has applications in quantum information processing and other quantum technologies. We demonstrate two methods, both using just a single artificial atom, enabling dynamic control over microwave light velocities in waveguide quantum electrodynamics (QED). Our methods are based on two distinct mechanisms harnessing the balance between radiative decay and nonradiative decoherence rates of a superconducting artificial atom in front of a mirror. In the first method, we tune the radiative decay of the atom using interference effects due to the mirror; in the second method, we pump the atom to effectively control its nonradiative decoherence. When the half of the radiative decay rate exceeds the nonradiative decoherence rate, we observe positive group delay; conversely, dominance of the nonradiative decoherence results in negative group delay. Our results advance signal-processing capabilities in waveguide QED.
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http://dx.doi.org/10.1103/fkzb-fxv4 | DOI Listing |
Phys Rev Lett
August 2025
City University of Hong Kong, Department of Physics, Kowloon, Hong Kong SAR 999077, China.
The ability to slow down light at the single-photon level has applications in quantum information processing and other quantum technologies. We demonstrate two methods, both using just a single artificial atom, enabling dynamic control over microwave light velocities in waveguide quantum electrodynamics (QED). Our methods are based on two distinct mechanisms harnessing the balance between radiative decay and nonradiative decoherence rates of a superconducting artificial atom in front of a mirror.
View Article and Find Full Text PDFJ Chem Theory Comput
August 2025
Department of Chemistry, University at Buffalo, the State University of New York, Buffalo, New York 14260-3000, United States.
The paper reports a computational study of excited-state dynamics in pristine and divacancy-defect-containing monolayer black phosphorus (ML-BP), with the primary focus on the nonradiative recombination of the lowest energy exciton. The excitonic effects are treated using time-dependent density functional theory (TD-DFT) combined with several hybrid density functionals, while the excitonic dynamics is modeled using a variety of quantum-classical nonadiabatic molecular dynamics methods. Our calculations reveal that the nonradiative recombination rates obtained from the overcoherent quantum dynamics increase with the increase of the exact exchange fraction in hybrid functionals which increases the corresponding - energy gaps.
View Article and Find Full Text PDFJ Chem Phys
July 2025
College of Chemistry and Materials Science, Hebei University, Baoding 071002, People's Republic of China.
CdSexTe1-x is one of the most commercially successful absorber materials for thin-film solar cells, where Se doping is crucial for enhancing device efficiency. However, the microscopic control mechanisms are not yet clear. This study combines density functional theory-based electronic structure with nonadiabatic molecular dynamics to systematically analyze the nonradiative electron-hole recombination of CdTe and Se-doped systems.
View Article and Find Full Text PDFJ Phys Chem Lett
July 2025
College of Chemistry and Materials Science, Hebei University, Baoding 071002, P. R. China.
Nonradiative electron-hole recombination is a key factor in the performance bottleneck of perovskite optoelectronic devices, and its rate is highly dependent on nonadiabatic (NA) coupling and electron coherence. Traditional first-principles-based NA coupling calculations have the problems of high computational overhead and low efficiency, which limit their wide application in complex systems such as doping regulation. This work adopts a CsPbI and Ge-doped system as the research object, combines density functional theory with nonadiabatic molecular dynamics (NAMD), uses Hammes-Schiffer-Tully (HST) and norm-preserving interpolation (NPI) strategies to systematically evaluate four types of NA couplings, and introduces a variety of deep learning models (including four convolutional neural networks and three Transformer structures) to achieve efficient prediction.
View Article and Find Full Text PDFJ Phys Chem Lett
June 2025
Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States.
Nonadiabatic dynamics describe the nonradiative relaxation of excited states in semiconducting materials which determine the efficiency of optoelectronic devices. Due to the computational complexity of modeling the coupled electronic-nuclear dynamics approximations are required. In the solid state a common approximation is the independent orbital approximation (IOA) as the electronic basis for surface-hopping trajectories describing nuclear dynamics.
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