Tunable decoherence in the vicinity of a normal metal–superconducting junction

Abstract

The decoherence rate of a quantum dot coupled to a fluctuating environment described by a normal-metal superconductor junction is considered. The density-density correlator at low frequencies constitutes the kernel which enters the calculation of the phase coherence time. The density fluctuations are connected to the finite frequency current-current correlations in the point contact via the continuity equation. Below and above the gap, at zero temperature the density correlator contains spatial oscillations at half of the Fermi wave length on the normal side. As the bias crosses the superconducting gap, the opening of new scattering channels enhances the decoherence rate dramatically, suggesting the possibility of tuning the decoherence rate in a controllable manner.

Quantum dot dephasing by fractional quantum Hall edge states

“…This is understood from the continuity equation, which relates the current operator to the density operator. 10 The theoretical predictions of noise in the weak and strong BS limits have been verified in point-contact experiments at filling factor =1/3,1/5. 19,20 At zero temperature, the nonequilibrium dephasing rate of Eq.…”

“…A general theoretical framework for describing dephasing has been presented in Ref. 7,8, and was applied to a quantum Hall geometry 9 , and to a normal metal-superconductor QPC 10 . In all the above, the dephasing rate typically increases when the voltage bias of the QPC is increased.…”

“…strong BS limit have been verified in point contact experiments at filling factor ν = 1/3, 1/5 19,20 . This is understood from the continuity equation, which relates the current operator to the density operator 10 . At zero temperature, the non-equilibrium dephasing rate of Eq.…”

Dephasing due to a fluctuating fractional quantum Hall edge current

“…Charge fluctuations in the QPC create a fluctuating potential at the dot, modulate its electron level, and destroy the coherence of the transmission through the dot 2 . Theoretical studies for describing this dephasing have been developped 3,4 , and were applied to a quantum Hall geometry 5 , and to a normal metal-superconductor QPC 6 .…”