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[Advances In Atomic, Molecular, and Optical Physics] Volume 67 || Zeeman Spectroscopy in Penning Traps
摘要： Penning traps are the instruments of choice to determine the magnetic moments of long lived or stable charged particles. The virtual absence of collisions with background molecules when working in ultra-high vacuum, the small volume which the trapped particles occupy at low kinetic energies, and the extremely long observation and coherence times allow for very high precision in Zeeman spectroscopy. When applied to singly ionized multielectron atoms the experiments serve for tests of atomic structure calculations. The magnetic moments in few-electron systems such as hydrogen- or lithium-like highly charged ions can be calculated with remarkable precision in the frame of bound-state quantum electrodynamics. The results not only test corresponding calculations but also have impact on fundamental particle properties and fundamental constants. The chapter summarizes results obtained in recent years on various low- and highly charged systems.
关键词： magnetic moments,Penning traps,fundamental constants,quantum electrodynamics,Zeeman spectroscopy
更新于2025-09-10 09:29:36
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Microwave dual-mode resonators for coherent spin-photon coupling
摘要： We implement superconducting Yttrium barium copper oxide planar resonators with two fundamental modes for circuit quantum electrodynamics experiments. We first demonstrate good tunability in the resonant microwave frequencies and in their interplay, as emerges from the dependence of the transmission spectra on the device geometry. We then investigate the magnetic coupling of the resonant modes with bulk samples of 2,2-diphenyl-1-picrylhydrazyl organic radical spins. The transmission spectroscopy performed at low temperature shows that the coherent spin-photon coupling regime with the spin ensembles can be achieved by each of the resonator modes. The analysis of the results within the framework of the input-output formalism and by means of entropic measures demonstrates coherent mixing of the degrees of freedom corresponding to two remote spin ensembles and, with a suitable choice of the geometry, the approaching of a regime with spin-induced mixing of the two photon modes.
关键词： coherent spin-photon coupling,circuit quantum electrodynamics,Microwave dual-mode resonators,superconducting Yttrium barium copper oxide,2,2-diphenyl-1-picrylhydrazyl organic radical spins
更新于2025-09-10 09:29:36
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Purcell-Dicke enhancement of the Casimir-Polder potential
摘要： The emission by an initially completely inverted ensemble of two-level atoms in the long-wavelength regime is simultaneously enhanced by both collective effects (Dicke effect) and dielectric environments (Purcell effect), thus giving rise to a combined Purcell–Dicke effect. We study this effect by treating the ensemble of N atoms as a single effective N + 1-level "Dicke atom" which couples to the environment-assisted quantum electrodynamic field. We find that an environment can indeed alter the superradiant emission dynamics, as exemplified using a perfectly conducting plate. As the emission acquires an additional anisotropy in the presence of the plate, we find an associated resonant Casimir-Polder potential for the atom that is collectively enhanced and that exhibits a superradiant burst in its dynamics. An additional tuneability of the effect is introduced by applying an external driving laser field.
关键词： superradiant emission,quantum electrodynamics,Purcell-Dicke effect,Casimir-Polder potential
更新于2025-09-09 09:28:46
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Quadrature squeezing of the mechanical mode in a superconducting electromechanical system
摘要： We propose a scheme for realizing quadrature squeezing of the mechanical mode in a superconducting electromechanical system, where a nanomechanical resonator (NAMR) is coupled to a superconducting transmission line resonator (STLR) via a superconducting quantum interference device (SQUID), and the SQUID acts as a qubit. Under a large detuning condition, we use the Fr?hlich-Nakajima transformation to adiabatically eliminate the qubit and obtain an effective Hamiltonian for the STLR and the NAMR. Our results show that a strong squeezing effect (beyond 3 dB limit) can occur in the NAMR, and the squeezing degree can be optimized by controlling the strength of the driving field and the dissipation ratio of the system. One of the most notable features of our results is the universality, i.e. the results only depend on a few scaled quantities, not on too many parameters.
关键词： squeezed states,quantum electrodynamics,quantum optics,coupled resonators
更新于2025-09-04 15:30:14
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Cavity-QED interactions of several atoms
摘要： We study many-atom van der Waals forces arising from reversible atom–field interactions in cavity quantum electrodynamics by using a dressed-state approximation. In the most general case, a single-mode Dicke model for atoms, sharing an arbitrary number of excitations, placed in an imperfect cavity has been developed that leads to the vdW potential of such system. As special cases, we consider the single-excitation Dicke model and also the case of one atom in the presence of multi-photon excitation inside the cavity. In most of the paper, it is assumed that the atoms are distributed symmetrically with respect to the mode structure. This will decouple all asymmetric states, allowing us to ignore them throughout our calculations. The impact of asymmetric states is taken into account for a system wherein one atom, freely placed in a cavity, together with n ? 1 equally-coupled atoms is interacting with the cavity field. By assuming broadened Lorentzian modes instead of sharp ones, the cavity imperfections have been added to the calculations. The position dependence of the effective Rabi frequency is studied for the example of a planar cavity.
关键词： cavity quantum electrodynamics,van der Waals forces,planar cavity,dressed-state approximation,Dicke model,Rabi frequency
更新于2025-09-04 15:30:14
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Entanglement, nonclassical properties, and geometric phase in circuit quantum electrodynamics with relativistic motion
摘要： In this work, we study qualitatively the nonclassical properties, nonlocal correlation, and geometric phase in a superconducting qubit system connected to a transmission line resonator (TLR) within a circuit quantum electrodynamics setup, where the modulation of the coupling strength can imitate the harmonic motion of the superconducting system at relativistic speeds. We analyze the effects of the relativistic motion on these quantum quantifiers under the influence of the physical parameters implicated in the whole quantum system state. Furthermore, the relationship between the different quantifiers is explored. Our results may open new perspectives to understand and explore the relativistic phenomena on the comportment of the quantum quantifiers for new applications in superconducting quantum technologies.
关键词： E. Nonclassical properties and correlation,B. Superconducting qubit system,A. Solid state systems,C. Transmission line resonator,D. Circuit quantum electrodynamics
更新于2025-09-04 15:30:14
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Conserving approximations in cavity quantum electrodynamics: Implications for density functional theory of electron-photon systems
摘要： By analyzing the many-body problem for nonrelativistic electrons strongly coupled to photon modes of a microcavity I derive the exact momentum/force balance equation for cavity quantum electrodynamics. Implications of this equation for the electron self-energy and the exchange-correlation potential of the quantum electrodynamic time-dependent density functional (QED-TDDFT) are discussed. In particular I generalize the concept of (cid:2) derivability to construct approximations which ensure the correct momentum balance. It is shown that a recently proposed optimized effective potential approximation for QED-TDDFT is conserving, and its possible improvements are discussed.
关键词： cavity quantum electrodynamics,density functional theory,conserving approximations,momentum balance,electron-photon systems
更新于2025-09-04 15:30:14
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Resonance Energy Transfer in Arbitrary Media: Beyond the Point Dipole Approximation
摘要： In this work, we present a comprehensive theoretical and computational study of donor/acceptor resonance energy transfer (RET) beyond the dipole approximation, in arbitrary inhomogeneous and dispersive media. The theoretical method extends Fo?rster theory for RET between particles (molecules or nanoparticles) to the case where higher multipole transitions in the donor and/or acceptor play a significant role in the energy transfer process. In our new formulation, the energy transfer matrix element is determined by a fully quantum electrodynamic expression, but its evaluation requires only classical electrodynamics calculations. By means of a time domain electrodynamical approach (TED), the matrix element evaluation involves the electric and magnetic fields generated by the donor and evaluated at the position of the acceptor, including fields associated with transition electric dipoles, electric quadrupoles, and magnetic dipoles in the donor, and the acceptor response to the electric and magnetic fields and to the electric field gradient. As an illustration of the benefits of the new formalism, we tested our method with a 512 atom lead sulfide (PbS) quantum dot as the donor/acceptor in vacuum, and with spherical nanoparticles (toy model) possessing designed transition multipoles. This includes an analysis of the effects of interferences between multipoles in the energy transfer rate. The results show important deviations from the conventional Fo?rster dipole theory that are important even in vacuum but that can be amplified by interaction with a plasmonic nanoparticle.
关键词： multipole transitions,resonance energy transfer,plasmonic nanoparticle,quantum electrodynamics,dipole approximation,RET
更新于2025-09-04 15:30:14