The paper discusses the analytical investigation of the occurrence of coherent optical transient processes such as dynamic Stark effect and free induction decay in direct-gap semiconductor quantum wires with thickness and width smaller than the bulk Wannier-Mott exciton Bohr radius. The role of a moderately strong magnetic field has been critically evaluated in the occurrence of the transient processes. The analysis is based upon the time dependent perturbation treatment of the coherent radiation-semiconductor interaction model under near band gap resonant excitation regime. The excitation intensity is kept below the Mott transition regime. Numerical estimates made for a GaAs/AlGaAs quantum wire irradiated by femtosecond pulse Ti:Sapphire laser establishes that the Stark shift, Stark broadening as well as free induction decay are all considerably influenced by the magnetic field. Moreover, the wire width also affects Stark splittings.The paper discusses the analytical investigation of the occurrence of coherent optical transient processes such as dynamic Stark effect and free induction decay in direct-gap semiconductor quantum wires with thickness and width smaller than the bulk Wannier-Mott exciton Bohr radius. The role of a moderately strong magnetic field has been critically evaluated in the occurrence of the transient processes. The analysis is based upon the time dependent perturbation treatment of the coherent radiation-semiconductor interaction model under near band gap resonant excitation regime. The excitation intensity is kept below the Mott transition regime. Numerical estimates made for a GaAs/AlGaAs quantum wire irradiated by femtosecond pulse Ti:Sapphire laser establishes that the Stark shift, Stark broadening as well as free induction decay are all considerably influenced by the magnetic field. Moreover, the wire width also affects Stark splittings.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIESep 25, 20010 citations

Experimental demonstration of a robust and scalable flux qubit

R. Harris, J. Johansson, A. J. Berkley +16 more

A rf--superconducting quantum interference device (SQUID) flux qubit that is robust against fabrication variations in Josephson-junction critical currents and device inductance has been implemented. Measurements of the persistent current and of the tunneling energy between the two lowest-lying states, both in the coherent and incoherent regimes, are presented. These experimental results are shown to be in agreement with predictions of a quantum-mechanical Hamiltonian whose parameters were independently calibrated, thus justifying the identification of this device as a flux qubit. In addition, measurements of the flux and critical current noise spectral densities are presented that indicate that these devices with Nb wiring are comparable to the best Al wiring rf SQUIDs reported in the literature thus far, with a $1/f$ flux noise spectral density at 1 Hz of ${1.3}_{\ensuremath{-}0.5}^{+0.7}\text{ }\ensuremath{\mu}{\ensuremath{\Phi}}_{0}/\sqrt{\text{Hz}}$. An explicit formula for converting the observed flux noise spectral density into a free-induction-decay time for a flux qubit biased to its optimal point and operated in the energy eigenbasis is presented.A rf--superconducting quantum interference device (SQUID) flux qubit that is robust against fabrication variations in Josephson-junction critical currents and device inductance has been implemented. Measurements of the persistent current and of the tunneling energy between the two lowest-lying states, both in the coherent and incoherent regimes, are presented. These experimental results are shown to be in agreement with predictions of a quantum-mechanical Hamiltonian whose parameters were independently calibrated, thus justifying the identification of this device as a flux qubit. In addition, measurements of the flux and critical current noise spectral densities are presented that indicate that these devices with Nb wiring are comparable to the best Al wiring rf SQUIDs reported in the literature thus far, with a $1/f$ flux noise spectral density at 1 Hz of ${1.3}_{\ensuremath{-}0.5}^{+0.7}\text{ }\ensuremath{\mu}{\ensuremath{\Phi}}_{0}/\sqrt{\text{Hz}}$. An explicit formula for converting the observed flux noise spectral density into a free-induction-decay time for a flux qubit biased to its optimal point and operated in the energy eigenbasis is presented.

arXiv:0909.4321Physical Review BApr 7, 2010180 citations

Impurity effects in quantum wires

G. Gómez-Santos

Springer eBooksApr 6, 20080 citations

Transport in Single Channel Quantum Wires

Hermann Grabert

arXiv:cond-mat/0107175Springer eBooksJan 1, 20024 citations

Femtosecond Free Induction Decay Beats in Nd3+:YAG Crystal

Ryuzi Yano, Naoshi Uesugi

Femtosecond free induction decay (FID) beats were observed for the 4F3/2 - 4I9/2 transition of Nd3+ ions doped in Y3Al5O12 (YAG) crystal at room temperature using a mode-locked Ti3+:Al2O3 laser. This is the first observation of room-temperature dephasing processes in the time domain for rare-earth ion doped materials. The FID beat signal shows a dip structure produced by the interference between the pump pulse and the FID signal, and a quantum beat. The FID signal became large and comparable to the pump pulse as the crystal length was increased. The FID intensity evolution due to the pulse propagation is explained well by phenomenological equations.Femtosecond free induction decay (FID) beats were observed for the 4F3/2 - 4I9/2 transition of Nd3+ ions doped in Y3Al5O12 (YAG) crystal at room temperature using a mode-locked Ti3+:Al2O3 laser. This is the first observation of room-temperature dephasing processes in the time domain for rare-earth ion doped materials. The FID beat signal shows a dip structure produced by the interference between the pump pulse and the FID signal, and a quantum beat. The FID signal became large and comparable to the pump pulse as the crystal length was increased. The FID intensity evolution due to the pulse propagation is explained well by phenomenological equations.

Japanese Journal of Applied PhysicsDec 1, 19971 citation

1/f

flux noise spectral density at 1 Hz of ${1.3}_{\ensuremath{-}0.5}^{+0.7}\text{ }\ensuremath{\mu}{\ensuremath{\Phi}}_{0}/\sqrt{\text{Hz}}$. An explicit formula for converting the observed flux noise spectral density into a free-induction-decay time for a flux qubit biased to its optimal point and operated in the energy eigenbasis is presented.