1,097 research outputs found
Dynamical suppression of telegraph and 1/f noise due to quantum bistable fluctuator
We study dynamical decoupling of a qubit from non gaussian quantum noise due
to discrete sources, as bistable fluctuators and 1/f noise. We obtain analytic
and numerical results for generic operating point. For very large pulse
frequency, where dynamic decoupling compensates decoherence, we found universal
behavior. At intermediate frequencies noise can be compensated or enhanced,
depending on the nature of the fluctuators and on the operating point. Our
technique can be applied to a larger class of non-gaussian environments.Comment: Revtex 4, 5 pages, 3 figures. Title revised and some other minor
changed. Final version as published in PR
Electron transfer in the nonadiabatic regime: Crossover from quantum-mechanical to classical behaviour
We study nonadiabatic electron transfer within the biased spin-boson model.
We calculate the incoherent transfer rate in analytic form at all temperatures
for a power law form of the spectral density of the solvent coupling. In the
Ohmic case, we present the exact low temperature corrections to the zero
temperature rate for arbitrarily large bias energies between the two redox
sites. Both for Ohmic and non-Ohmic coupling, we give the rate in the entire
regime extending from zero temperature, where the rate depends significantly on
the detailed spectral behaviour, via the crossover region, up to the classical
regime. For low temperatures, the rate shows characteristic quantum features,
in particular the shift of the rate maximum to a bias value below the
reorganization energy, and the asymmetry of the rate around the maximum. We
study in detail the gradual extinction of the quantum features as temperature
is increased.Comment: 17 pages, 4 figures, to be published in Chem. Phy
Decoherence due to telegraph and 1/f noise in Josephson qubits
We study decoherence due to random telegraph and 1/f noise in Josephson
qubits. We illustrate differences between gaussian and non gaussian effects at
different working points and for different protocols. Features of the
intrinsically non-gaussian and non-Markovian low-frequency noise may explain
the rich physics observed in the spectroscopy and the dynamics of charge based
devices.Comment: 6 pages, 4 figures. Proceedings of the International Symposium on
Mesoscopic Superconductivity and Spintronics 2004 (MS+S2004), Atsugi, Japa
Characterization of coherent impurity effects in solid state qubits
We propose a characterisation of the effects of bistable coherent impurities
in solid state qubits. We introduce an effective impurity description in terms
of a tunable spin-boson environment and solve the dynamics for the qubit
coherences. The dominant rate characterizing the asymptotic time limit is
identified and signatures of non-Gaussian behavior of the quantum impurity at
intermediate times are pointed out. An alternative perspective considering the
qubit as a measurement device for the spin-boson impurity is proposed.Comment: 4 pages, 5 figures. Replaced with published version, minor change
Hidden entanglement, system-environment information flow and non-Markovianity
It is known that entanglement dynamics of two noninteracting qubits, locally
subjected to classical environments, may exhibit revivals. A simple explanation
of this phenomenon may be provided by using the concept of hidden entanglement,
which signals the presence of entanglement that may be recovered without the
help of nonlocal operations. Here we discuss the link between hidden
entanglement and the (non-Markovian) flow of classical information between the
system and the environment.Comment: 9 pages, 2 figures; proceedings of the conference IQIS 2013,
September 24-26 2013, Como, Ital
Hidden entanglement in the presence of random telegraph dephasing noise
Entanglement dynamics of two noninteracting qubits, locally affected by
random telegraph noise at pure dephasing, exhibits revivals. These revivals are
not due to the action of any nonlocal operation, thus their occurrence may
appear paradoxical since entanglement is by definition a nonlocal resource. We
show that a simple explanation of this phenomenon may be provided by using the
(recently introduced) concept of "hidden" entanglement, which signals the
presence of entanglement that may be recovered with the only help of local
operations.Comment: 8 pages, 1 figure, submitted to Physica Scripta on September 17th
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