Nanosecond Dynamics of Single-Molecule Fluorescence Resonance Energy Transfer

Motivated by recent experiments on photon statistics from individual dye pairs planted on biomolecules and coupled by fluorescence resonance energy transfer (FRET), we show here that the FRET dynamics can be modelled by Gaussian random processes with colored noise. Using Monte-Carlo numerical simulations, the photon intensity correlations from the FRET pairs are calculated, and are turned out to be very close to those observed in experiment. The proposed stochastic description of FRET is consistent with existing theories for microscopic dynamics of the biomolecule that carries the FRET coupled dye pairs.Comment: 8 pages, 1 figure. accepted to J.Phys.Chem.

Nonclassical Imaging for a quantum search of trapped ions

We discuss a simple search problem which can be pursued with different methods, either on a classical or on a quantum basis. The system is represented by a chain of trapped ions. The ion to be searched is a member of that chain, consists, however, of an isotopic species different to the others. It is shown that the classical imaging may lead as fast to the final result as the quantum imaging. However, for the discussed case the quantum method gives more flexibility and higher precision when the number of ions considered in the chain is increasing. In addition, interferences are observable even when the distances between the ions is smaller than half a wavelength of the incident light.Comment: 5 pages, 5 figure

Quantum properties of the codirectional three-mode Kerr nonlinear coupler

We investigate the quantum properties for the codirectional three-mode Kerr nonlinear coupler. We investigate single-, two- and three-mode quadrature squeezing, Wigner function and purity. We prove that this device can provide richer nonclassical effects than those produced by the conventional coupler, i.e. the two-mode Kerr coupler. We show that it can provide squeezing and the quadrature squeezing exhibiting leaf-revival-collapse phenomenon in dependence on the values of the interaction parameters. In contrast to the conventional Kerr coupler two different forms of cat states can be simultaneously generated in the waveguides. We deduce conditions required for the complete disentanglement between the components of the system.Comment: 23 pages, 6 figure

Single microwave photon detection in the micromaser

High efficiency single photon detection is an interesting problem for many areas of physics, including low temperature measurement, quantum information science and particle physics. For optical photons, there are many examples of devices capable of detecting single photons with high efficiency. However reliable single photon detection of microwaves is very difficult, principally due to their low energy. In this paper we present the theory of a cascade amplifier operating in the microwave regime that has an optimal quantum efficiency of 93%. The device uses a microwave photon to trigger the stimulated emission of a sequence of atoms where the energy transition is readily detectable. A detailed description of the detector's operation and some discussion of the potential limitations of the detector are presented.Comment: 8 pages, 5 figure

Interference-induced peak splitting in EUV superfluorescence

We investigate the laser-induced quantum interference in EUV superfluorescence occurring in a dense gas of $\Lambda$-type helium atoms coupled by a coherent laser field in the visible region. Due to the constructive interatomic and intraatomic interferences, the superfluorescence can split in two pulses conveniently controlled by the gas density and intensity of the driving field, suggesting potential applications for pump-probe experiments.Comment: 3 pages, 3 figure

Higher-order squeezing for the codirectional Kerr nonlinear coupler

In this Letter we study the evolution of the higher-order squeezing, namely, $n$th-order single-mode squeezing, sum- and difference-squeezing for the codirectional Kerr nonlinear coupler. We show that the amount of squeezing decreases when $n$, i.e. the squeezing order, increases. For specific values of the interaction parameters squeezing factors exhibit a series of revival-collapse phenomena, which become more pronounced when the value of $n$ increases. Sum-squeezing can provide amounts of squeezing greater than those produced by the $n$th higher-order ($n\geq 2$) squeezing for the same values of interaction parameters and can map onto amplitude-squared squeezing. Further, we prove that the difference-squeezing is not relevant measure for obtaining information about squeezing from this device.Comment: 13 pages, 3 figure

Entanglement of bosonic modes of nonplanar molecules

Entanglement of bosonic modes of material oscillators is studied in the context of two bilinearly coupled, nonlinear oscillators. These oscillators are realizable in the vibrational-cum-bending motions of C-H bonds in dihalomethanes. The bilinear coupling gives rise to invariant subspaces in the Hilbert space of the two oscillators. The number of separable states in any invariant subspace is one more than the dimension of the space. The dynamics of the oscillators when the initial state belongs to an invariant subspace is studied. In particular, the dynamics of the system when the initial state is such that the total energy is concentrated in one of the modes is studied and compared with the evolution of the system when the initial state is such wherein the modes share the total energy. The dynamics of quantities such as entropy, mean of number of quanta in the two modes and variances in the quadratures of the two modes are studied. Possibility of generating maximally entangled states is indicated.Comment: 21 pages, 6 figure

Quantum dynamics via a hidden Liouville space

Quantum dynamics for arbitrary system are traditionally realized by time evolutions of wave functions in Hilbert space and/or density operators in Liouville space. However, the traditional simulations may occasionally turn out to be challenging for the quantum dynamics, particularly those governed by the nonlinear Hamiltonians. In this letter, we introduce a nonstandard iterative technique where time interval is divided into a large number of discrete subintervals with an ultrashort duration; and the Liouville space is briefly expanded with an additional (virtual) space only within these subintervals. We choose two-state spin raising and lowering operators for virtual space operators because of their simple algebra. This tremendously reduces the cost of time-consuming calculations. We implement our technique for an example of a charged particle in both harmonic and anharmonic potentials. The temporal evolutions of the probability for the particle being in the ground state are obtained numerically and compared to the analytical solutions. We further discuss the physics insight of this technique based on a thought-experiment. Successive processes intrinsically 'hitchhiking' via virtual space in discrete ultrashort time duration, are the hallmark of our simple iterative technique. We believe that this novel technique has potential for solving numerous problems which often pose a challenge when using the traditional approach based on time-ordered exponentials.Comment: 7 pages, 3 figure

The study of the spatio-temporal dynamics of intracellular ATP in macrophage efferocytosis

自治医科大学博士（医学）令和4年度thesi