Persistent narrowing of nuclear-spin fluctuations in InAs quantum dots using laser excitation

TL;DR

This paper demonstrates a method to suppress nuclear spin fluctuations in InAs quantum dots using laser excitation, significantly extending electron spin coherence times by stabilizing nuclear spins through dynamic nuclear polarization feedback.

Contribution

It introduces a laser-based technique to achieve long-lasting nuclear spin narrowing in quantum dots, simplifying coherence enhancement without complex pulse sequences.

Findings

Nuclear spin fluctuations are suppressed for over one second in dark conditions.

Electron spin coherence time (T2*) is significantly increased.

The method is simpler than traditional spin echo or dynamic decoupling techniques.

Abstract

We demonstrate the suppression of nuclear spin fluctuations in an InAs quantum dot and measure the timescales of the spin narrowing effect. By initializing for tens of milliseconds with two continuous wave diode lasers, fluctuations of the nuclear spins are suppressed via the hole assisted dynamic nuclear polarization feedback mechanism. The fluctuation narrowed state persists in the dark (absent light illumination) for well over one second even in the presence of a varying electron charge and spin polarization. Enhancement of the electron spin coherence time (T2*) is directly measured using coherent dark state spectroscopy. By separating the calming of the nuclear spins in time from the spin qubit operations, this method is much simpler than the spin echo coherence recovery or dynamic decoupling schemes.