The quantum electrodynamical theory of coherent fluorescence resonance energy transfer (FRET) between two dipoles (free atoms, molecules or dopant centres in crystalline matrices at low temperature conditions) in an arbitrary non-dissipative environment is elaborated using a canonical quantization scheme. It is shown that population dynamics of both atoms can be expressed in terms of a classical Green function. This general theory corresponds well to the problem of description of controllable quantum manipulations under the donor-acceptor system (e.g. its application for FRET scanning near-field optical microscopy-based quantum computing). In addition, its usefulness is illustrated for the case of coherent FRET in free space and for the case when atoms are placed near an ideally conducting plane. The possibility of creating an entangled state of three atoms is demonstrated.
The quantum electrodynamical theory of coherent fluorescence resonance energy transfer (FRET) between two dipoles (free atoms, molecules or dopant centres in crystalline matrices at low temperature conditions) in an arbitrary non-dissipative environment is elaborated using a canonical quantization scheme. It is shown that population dynamics of both atoms can be expressed in terms of a classical Green function. This general theory corresponds well to the problem of description of controllable quantum manipulations under the donor-acceptor system (e.g. its application for FRET scanning near-field optical microscopy-based quantum computing). In addition, its usefulness is illustrated for the case of coherent FRET in free space and for the case when atoms are placed near an ideally conducting plane. The possibility of creating an entangled state of three atoms is demonstrated.
The coherent Fluorescence Resonance Energy Transfer (FRET) combined with Scanning Near-Field Optical Microscopy (SNOM) are proposed for the creation of complex and nonlocal entangled states involving hundreds of atoms. Micro- and milli-second decoherence times of the electron excitation occur for rare-earth dopant ions in crystals at low temperatures, and we show that the characteristic coherent FRET distances for such systems are of the order of 20 nm. Thus, both position and time precision necessary for the quantum manipulation can be attained by modern SNOM technology. Potential applications for quantum computing are discussed.
The coherent energy transfer efficiency of a pair of two-level atoms is studied theoretically and its mathematical expression has been deduced. The problem of atoms coherent energy transfer theory is treated by quantum perturbation theory and equivalent method replacing atomic dipole field with light field of the same frequency. The detuning between the donor atom transition frequency and the acceptor atom transition frequency has been studied in the theory. With the increase of the detuning of the two-atomic transition frequency, the energy transfer efficiency decays rapidly. In the case of two-atomic transition frequency resonance, the coherent resonance energy transfer efficiency is directly proportional to the square of the sine of the minus three power of the distance between two atoms and the energy transfer efficiency is periodically decaying over time. The coherent resonance energy transfer efficiency is inversely proportional to the six power of the distance between the two atoms in the first-order approximation.
The polarization of the resonance fluorescence of interacting atoms and the transfer of coherence, due to the exchange of excitation, are studied theoretically. The treatment is for the general case where both the excited and the ground states can have arbitrary angular momenta, except that they can be connected to each other by an allowed transition. Electrostatic dipole–dipole interaction and electromagnetic radiative interaction are considered simultaneously as the perturbations on the system. Heitler and Ma's generalized time-dependent perturbation method is used. The system is quantized with respect to the space-fixed z axis and a static magnetic field along the z axis may be present, so that the magnetic sublevels (m, m′, etc., for the excited state J, and α, β, etc., for the ground state J′) are not necessarily degenerate. The intensity of the scattered light of a given polarization, in a given direction, is expressed as a function of kR (where ℏck is the energy of excitation and R is the internuclear distance), and of the orientation of R with respect to z axis. The matrix elements (ℏ / 2)γmβ,αm′ and Vmβ,αm′, which cause resonant transfer of excitation between two atoms through radiative and electrostatic interaction, respectively, are also expressed as a function of kR, and of the orientation of R. For randomly oriented atoms, the polarization after being averaged over the random orientation of R becomes a function of kR. Numerical calculations have been carried out for S01 → 1P1 transition. The coherence is shown to be conserved upon resonant transfer of excitation when R is parallel to the quantization axis.
We investigate the interaction between light and molecular systems modeled as quantum emitters coupled to a multitude of vibrational modes via a Holstein-type interaction. We follow a quantum Langevin equations approach that allows for analytical derivations of absorption and fluorescence profiles of molecules driven by classical fields or coupled to quantized optical modes. We retrieve analytical expressions for the modification of the radiative emission branching ratio in the Purcell regime and for the asymmetric cavity transmission associated with dissipative cross-talk between upper and lower polaritons in the strong coupling regime. We also characterize the Forster resonance energy transfer process between donor-acceptor molecules mediated by the vacuum or by a cavity mode.
We study coherent energy transfer of a single excitation and quantum entanglement in a dimer, which consists of a donor and an acceptor modeled by two two-level systems. Between the donor and the acceptor, there exists a dipole-dipole interaction, which provides the physical mechanism for coherent energy transfer and entanglement generation. The donor and the acceptor couple to two independent heat baths with diagonal couplings that do not dissipate the energy of the noncoupling dimer. Special attention is paid to the effect on single-excitation energy transfer and entanglement generation of the energy detuning between the donor and the acceptor and the temperatures of the two heat baths. It is found that, the probability for single-excitation energy transfer largely depends on the energy detuning in the low temperature limit. Concretely, the positive and negative energy detunings can increase and decrease the probability at steady state, respectively. In the high temperature limit, however, the effect of the energy detuning on the probability is negligibly small. We also find that the probability is negligibly dependent on the bath temperature difference of the two heat baths. In addition, it is found that quantum entanglement can be generated in the process of coherent energy transfer. As the bath temperature increases, the generated steady-state entanglement decreases. For a given bath temperature, the steady-state entanglement decreases with the increase of the absolute value of the energy detuning.
A Green's function formulation of the problem of resonance fluorescence from a system of identical two level atoms is presented. The general formulation is suitable for the investigation of a variety of nonlinear phenomena, e.g., propagation of electromagnetic waves inside the medium, fluorescence from a finite medium, optical bistability, atomic correlations, and additional side bands. Translational motion, collisions, Coulomb dipole–dipole interaction, excitation transfer, and local field corrections are also included in the basic equations. The effect of atom–atom correlations in the relaxation mechanism (radiative or collisional) is also taken into account. Finally, the results are also presented in the "generalized dressed atom" (GDA) representation. Applications of the general theory will be given in a future paper.