5,621 research outputs found
Theoretical analysis of continuously driven dissipative solid-state qubits
We study a realistic model for driven qubits using the numerical solution of
the Bloch-Redfield equation as well as analytical approximations using a
high-frequency scheme. Unlike in idealized rotating-wave models suitable for
NMR or quantum optics, we study a driving term which neither is orthogonal to
the static term nor leaves the adiabatic energy value constant. We investigate
the underlying dynamics and analyze the spectroscopy peaks obtained in recent
experiments. We show, that unlike in the rotating-wave case, this system
exhibits nonlinear driving effects.We study the width of spectroscopy peaks and
show, how a full analysis of the parameters of the system can be performed by
comparing the first and second resonance. We outline the limitations of the NMR
linewidth formula at low temperature and show, that spectrocopic peaks
experience a strong shift which goes much beyond the Bloch-Siegert shift of the
Eigenfrequency.Comment: Accepted for publication in Phys. Rev.
Stationary and transient leakage current in the Pauli spin blockade
We study the effects of cotunneling and a non-uniform Zeeman splitting on the
stationary and transient leakage current through a double quantum dot in the
Pauli spin blockade regime. We find that the stationary current due to
cotunneling vanishes at low temperature and large applied magnetic field,
allowing for the dynamical preparation of a pure spin ground state, even at
large voltage bias. Additionally, we analyze current that flows between
blocking events, characterized, in general, by a fractional effective charge
. This charge can be used as a sensitive probe of spin relaxation
mechanisms and can be used to determine the visibility of Rabi oscillations.Comment: v1: 4 pages; v2: 4 pages+ additional supplementary material, version
to appear in PR
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