Suppression of electron spin decoherence in a quantum dot

TL;DR

This paper demonstrates that dynamical decoupling protocols can significantly extend electron spin coherence times in quantum dots by effectively mitigating hyperfine-induced decoherence, even with realistic pulse delays.

Contribution

It provides a detailed numerical analysis of various dynamical decoupling protocols under realistic conditions, highlighting their effectiveness in prolonging electron spin coherence.

Findings

Both deterministic and randomized protocols improve coherence time.

Effective decoupling is possible with pulse separations larger than the coupling spectrum's upper cutoff.

The coupling spectrum's total width is a key factor in decoupling performance.

Abstract

The dominant source of decoherence for an electron spin in a quantum dot is the hyperfine interaction with the surrounding bath of nuclear spins. The decoherence process may be slowed down by subjecting the electron spin to suitable sequences of external control pulses. We investigate the performance of a variety of dynamical decoupling protocols using exact numerical simulation. Emphasis is given to realistic pulse delays and the long-time limit, beyond the domain where available analytical approaches are guaranteed to work. Our results show that both deterministic and randomized protocols are capable to significantly prolong the electron coherence time, even when using control pulse separations substantially larger than what expected from the {\em upper cutoff} frequency of the coupling spectrum between the electron and the nuclear spins. In a realistic parameter range, the {\em total width} of such a coupling spectrum appears to be the physically relevant frequency scale affecting the overall quality of the decoupling.