9,165 research outputs found
Transport and Noise of Entangled Electrons
We consider a scattering set-up with an entangler and beam splitter where the
current noise exhibits bunching behavior for electronic singlet states and
antibunching behavior for triplet states. We show that the entanglement of two
electrons in the double-dot can be detected in mesoscopic transport
measurements. In the cotunneling regime the singlet and triplet states lead to
phase-coherent current contributions of opposite signs and to Aharonov-Bohm and
Berry phase oscillations in response to magnetic fields. We analyze the Fermi
liquid effects in the transport of entangled electrons.Comment: 9 pages, Latex, uses lamuphys.sty (included), 1 eps figure embedded
with epsf, to appear in Proceedings of the XVI Sitges Conference (Lecture
Notes in Physics, Springer
Full control of qubit rotations in a voltage-biased superconducting flux qubit
We study a voltage-controlled version of the superconducting flux qubit
[Chiorescu et al., Science 299, 1869 (2003)] and show that full control of
qubit rotations on the entire Bloch sphere can be achieved. Circuit graph
theory is used to study a setup where voltage sources are attached to the two
superconducting islands formed between the three Josephson junctions in the
flux qubit. Applying a voltage allows qubit rotations about the y axis, in
addition to pure x and z rotations obtained in the absence of applied voltages.
The orientation and magnitude of the rotation axis on the Bloch sphere can be
tuned by the gate voltages, the external magnetic flux, and the ratio alpha
between the Josephson energies via a flux-tunable junction. We compare the
single-qubit control in the known regime alpha<1 with the unexplored range
alpha>1 and estimate the decoherence due to voltage fluctuations.Comment: 12 pages, 12 figures, 1 tabl
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