Engineering topics

Koshino, Kazuki

Publications and source records attributed to Koshino, Kazuki.

5 records

DOE OSTI2011

Theory of resonance fluorescence from a solid-state cavity QED system: Effects of pure dephasing

We theoretically analyze the resonance fluorescence of a solid-state cavity quantum electrodynamics (QED) system that consists of a quantum dot and a cavity. We clarify the effects of pure dephasing by investigating the elastic and inelastic scattering probabilities, the fluorescence power spectrum, and the energy exchange with the environment. Pure dephasing interactions with the environment both enhance nonresonant coupling between the dot and the cavity and enable the pump light to continuously absorb energy from the environment under appropriate conditions.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2011

Up-conversion dynamics for temporally entangled two-photon pulses

We analyze the up conversion of a two-photon pulse having temporal entanglement on the basis of a full quantum formalism that treats both photons and optical media quantum mechanically. We derive a formula of the up-converted photon wave function, which is applicable to arbitrary input two-photon states for a three-level system, as the simplest second-order nonlinear optical system. As the input, we employ three kinds of temporally entangled two-photon pulses: correlated, uncorrelated, and anticorrelated. We observe the up-conversion efficiency and the temporal profile of the up-converted photon. Our results reveal the crossover behavior of the up conversion from anticorrelation to correlation and show how the temporal correlation in the input is reflected in the up-conversion process.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2010

Photon statistics of atomic fluorescence after {pi}-pulse excitation

The photon statistics of atomic fluorescence after {pi}-pulse excitation is investigated in a system in which the input and output ports are connected to an atom. Since spontaneous decay during input pulse excitation occurs, the output pulse generally contains a multiphoton component with a certain probability. We quantitatively evaluate the probability of the output pulse containing multiple photons and determine the conditions for ideal single-photon generation.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2010

Deterministic photon-photon {radical}(SWAP)gate using a {Lambda} system

We theoretically present a method to realize a deterministic photon-photon {radical}(SWAP) gate using a three-level {Lambda} system interacting with single photons in reflection geometry. The {Lambda} system is used completely passively as a temporary memory for a photonic qubit; the initial state of the {Lambda} system may be arbitrary, and active control by auxiliary fields is unnecessary throughout the gate operations. These distinct merits make this entangling gate suitable for deterministic and scalable quantum computation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2010

Evaluation of multiphoton effects in down-conversion

Multiphoton effects in down-conversion are investigated based on the full-quantum multimode formalism by considering a three-level system as a prototype nonlinear system. We analytically derive the three-photon output wave function for two input photons, where one of the two input photons is down-converted and the other one is not. Using this output wave function, we calculate the down-conversion probability, the purity, and the fidelity to evaluate the entanglement between a down-converted photon pair and a non-down-converted photon. It is shown that the saturation effect occurs by multiphoton input and that it affects both the down-conversion probability and the quantum correlation between the down-converted photon pair and the non-down-converted photon. We also reveal the necessary conditions for multiphoton effects to be strong.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗