5,383 research outputs found
Coherent manipulation of electronic states in a double quantum dot
We investigate coherent time-evolution of charge states (pseudo-spin qubit)
in a semiconductor double quantum dot. This fully-tunable qubit is manipulated
with a high-speed voltage pulse that controls the energy and decoherence of the
system. Coherent oscillations of the qubit are observed for several
combinations of many-body ground and excited states of the quantum dots.
Possible decoherence mechanisms in the present device are also discussed.Comment: RevTe
Tunneling magnetoresistance in (La,Pr,Ca)MnO3 nanobridges
The manganite (La,Pr,Ca)MnO3 is well known for its micrometer scale phase
separation into coexisting ferromagnetic metallic and antiferromagnetic
insulating (AFI) regions. Fabricating bridges with widths smaller than the
phase separation length scale has allowed us to probe the magnetic properties
of individual phase separated regions. We observe tunneling magnetoresistance
across naturally occurring AFI tunnel barriers separating adjacent
ferromagnetic regions spanning the width of the bridges. Further, near the
Curie temperature, a magnetic field induced metal-to-insulator transition among
a discrete number of regions within the narrow bridges gives rise to abrupt and
colossal low-field magnetoresistance steps at well defined switching fields.Comment: 13 pages, 3 figures, submitted to Applied Physics Letter
Electron counting of single-electron tunneling current
Single-electron tunneling through a quantum dot is detected by means of a radio-frequency single-electron transistor.. Poisson statistics of single-electron-tunneling events are observed from frequency domain measurements, and individual tunneling events are detected in the time-domain measurements. Counting tunneling events gives an accurate current measurement in the saturated current regime, where electrons tunnel into the dot only from one electrode and tunnel out of the dot only to the other electrode. (C) 2004 American Institute of Physics.X119698sciescopu
Cross-Kerr-based information transfer processes
The realization of nonclassical states is an important task for many
applications of quantum information processing. Usually, properly tailored
interactions, different from goal to goal, are considered in order to
accomplish specific tasks within the general framework of quantum state
engineering. In this paper we remark on the flexibility of a cross-Kerr
nonlinear coupling in hybrid systems as an important ingredient in the
engineering of nonclassical states. The general scenario we consider is the
implementation of high cross-Kerr nonlinearity in cavity-quantum
electrodynamics. In this context, we discuss the possibility of performing
entanglement transfer and swapping between a qubit and a continuous-variable
state. The recently introduced concept of entanglement reciprocation is also
considered and shown to be possible with our scheme. We reinterpret some of our
results in terms of applications of a generalized Ising interaction to systems
of different nature.Comment: 8 pages, 4 figures, RevTeX
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