Rate of tunneling nonequilibrium quasiparticles in superconducting qubits

In superconducting qubits the lifetime of quantum states cannot be prolonged arbitrarily by decreasing temperature. At low temperature quasiparticles tunneling between the electromagnetic environment and superconducting islands takes the condensate state out of equilibrium due to charge imbalance. W...

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Bibliographic Details
Published in:Superconductor science & technology 2015-04, Vol.28 (4), p.45005-7
Main Author: Ansari, Mohammad H
Format: Article
Language:English
Subjects:
Fluctuation
Islands
Joining
Mathematical models
nonequilibrium quasiparticle
quantum state engineering
quantum tunneling in Josephson junctions
Qubits (quantum computing)
Superconductivity
Superconductors
Tunneling
Tunnelling
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Summary:In superconducting qubits the lifetime of quantum states cannot be prolonged arbitrarily by decreasing temperature. At low temperature quasiparticles tunneling between the electromagnetic environment and superconducting islands takes the condensate state out of equilibrium due to charge imbalance. We obtain the tunneling rate from a phenomenological model of non-equilibrium, where nonequilibrium quasiparticle tunnelling stimulates a temperature-dependent chemical potential shift in the superconductor. As a result we obtain a non-monotonic behavior for relaxation rate as a function of temperature. Depending on the fabrication parameters for some qubits, the lowest tunneling rate of nonequilibrium quasiparticles can take place only near the onset temperature below which nonequilibrium quasiparticles dominate over equilibrium one. Our theory also indicates that such tunnelings can influence the probability of transitions in qubits through a coupling to the zero-point energy of phase fluctuations.
ISSN:0953-2048
1361-6668
DOI:10.1088/0953-2048/28/4/045005