MULTIQUANTUM EPR

Alan Hájek, Jeffrey Bub

Małgorzata Jeleń, Wojciech Froncisz

A method to excite multiquantum transitions in a two-level system by application of continuous irradiation with a four-frequency microwave field is presented. The generated signal is composed of many intermodulation sidebands at different frequencies, which arise from the multiquantum transitions. These processes involve an odd number of photons, that are absorbed from, or emitted to two, three, or four fields. The correspondence between the frequency spectrum of the signal and possible pathways of multiquantum processes is found with recourse to the many mode Floquet theory. The reported experiments demonstrate the multiquantum origin of the detected intermodulation sidebands and their properties.

David Tong

Cheng Cheng

Doped with PbSe nanocrystals of different sizes, a multiquantum-dot-doped fiber amplifier (MQDFA) is proposed. Performance of the MQDFA is simulated by solving light-propagation equations and rate equations for a three-level system, and by applying superposed emission-absorption cross sections of the quantum dots (QDs). Pumped with 980 nm, this proposed MQDFA has characteristics of broader band, flatter gain, and lower noise than those of the erbium-doped fiber amplifiers at present. There is evidence to show that two factors, i.e., the equivalent Stokes shifts and the full wave at half maximum of the superposed spectra, dominate the performances of the MQDFA. Also, the equivalent Stokes shift and the FWHM are tunable by adopting the QDs in different sizes and choosing the doped number available. It is expected that such a MQDFA may be able to cover the all waveband in telecommunications if it is optimized on the doped number, sizes, and doped concentrations of the QDs.

Hidetsugu Sakaguchi, Kanji Umeda

The Gross–Pitaevskii equation for two-component rotating Bose–Einstein condensates with the Rashba-type spin–orbit (SO) coupling is studied with numerical simulations and variational analyses. A multiquantum vortex state becomes a ground state in a harmonic potential when mutual interaction is absent. When the attractive interaction is strong, the multiquantum vortex state exhibits modulational instability in the azimuthal direction, and a soliton-like state appears. When the repulsive interaction is strong, a vortex lattice state with a multiquantum vortex at the center is created. We find that the vortex lattice state is approximated at a linear combination of multiquantum vortex states.