Dynamical decoupling of a singlet-triplet qubit afflicted by a charge fluctuator

TL;DR

This paper investigates how dynamical decoupling sequences can mitigate charge noise in a singlet-triplet qubit, providing numerical and analytical insights into qubit decoherence and decay scaling.

Contribution

It introduces a numerical method for solving qubit dynamics under general pulse protocols and derives analytical solutions for different coupling regimes.

Findings

Qubit undergoes both dephasing and dissipative dynamics depending on the working point.

Decay time scales as a power law with the number of control pulses.

Analytical solutions elucidate the dynamics in weakly and strongly coupled regimes.

Abstract

The efficiency of dynamical decoupling pulse sequences in removing noise due to a charge fluctuator is studied for a singlet-triplet spin qubit. We develop a numerical method to solve the dynamical equations for all three components of the Bloch vector under a general pulse protocol, and with an arbitrary rotation axis. The qubit is shown to undergo both dephasing and dissipative dynamics, pending on its working point. Analytical solutions are found for the limits of weakly and strongly coupled fluctuators, shedding light on the distinct dynamics in the different parameter regimes. Scaling of the qubit decay time with the number of control pulses is found to follow a power law over a wide range of TLF parameters and qubit bias points.