82 research outputs found
Realization of a two-channel Kondo model with Josephson junction networks
We show that- in the quantum regime- a Josephson junction rhombi chain (i.e.
a Josephson junction chain made by rhombi formed by joining 4 Josephson
junctions) may be effectively mapped onto a quantum Hamiltonian describing
Ising spins in a transverse magnetic field with open boundary conditions. Then,
we elucidate how a Y-shaped network fabricated with 3 Josephson Junction Rhombi
chains may be used as a quantum device realizing the two channel Kondo model
recently proposed by Tsvelik. We point out that the emergence of a 2 channel
Kondo effect in this superconducting network may be probed through the
measurement of a pertinent Josephson current.Comment: 5 pages, 4 figures. To appear in EP
Classical and quantum Brownian motion in an electromagnetic field
The dynamics of a Brownian particle in a constant magnetic field and
time-dependent electric field is studied in the limit of white noise, using a
Langevin approach for the classical problem and the path-integral
Feynman-Vernon and Caldeira-Leggett framework for the quantum problem. We study
the time evolution in configuration space of the probability distribution of an
initial pure state represented by an asymmetrical Gaussian wave function and
show that it can be described as the superposition of (a) the classical motion
of the center of mass, (b) a rotation around the mean position, and (c) a
spreading processes along the principal axes.Comment: Presented at FQMT15-Frontiers of Quantum and Mesoscopic
Thermodynamics, July 27-August 1, 2015, Prague, Czech Republi
Entanglement Routers Using Macroscopic Singlets
We propose a mechanism where high entanglement between very distant boundary
spins is generated by suddenly connecting two long Kondo spin chains. We show
that this procedure provides an efficient way to route entanglement between
multiple distant sites. We observe that the key features of the entanglement
dynamics of the composite spin chain are remarkably well described using a
simple model of two singlets, each formed by two spins. The proposed
entanglement routing mechanism is a footprint of the emergence of a Kondo cloud
in a Kondo system and can be engineered and observed in varied physical
settings.Comment: 4 pages, 5 figures. Slightly longer than the published versio
Kondo Cloud Mediated Long Range Entanglement After Local Quench in a Spin Chain
We show that, in the gapless Kondo Regime, a single local quench at one end
of a Kondo spin chain induces a fast and long lived oscillatory dynamics. This
quickly establishes a high quality entanglement between the spins at the
opposite ends of the chain. This entanglement is mediated by the Kondo Cloud,
attains a constant high value independent of the length for large chains, and
shows thermal robustness. In contrast, when the Kondo cloud is absent, e.g. in
the gapped dimer regime, only finite size end to end effects can create some
entanglement on a much longer time-scale for rather short chains. By decoupling
one end of the chain during the dynamics one can distinguish between this
end-end effect which vanishes, and the global Kondo cloud mediated
entanglement, which persists. This quench approach paves the way to detect the
elusive Kondo cloud through the entanglement between two individual spins. Our
results show that non-perturbative cooperative phenomena from condensed matter
may be exploited for quantum information.Comment: 4 pages, 4 figures. All comments are welcome
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