Keeping a Single Qubit Alive by Experimental Dynamic Decoupling

TL;DR

This paper demonstrates that dynamic decoupling techniques, specifically Uhrig and CPMG sequences, can significantly extend the coherence time of a single trapped-ion qubit by nearly 100 times, enhancing quantum memory stability.

Contribution

The study extends the Hahn spin-echo technique to arbitrary polynomial frequency variations and analytically shows that Uhrig dynamic decoupling sequences are optimal for this purpose.

Findings

Nearly two orders of magnitude increase in qubit coherence time.

Uhrig and CPMG sequences provide comparable protection in ambient noise.

Analytical proof linking polynomial correction to Uhrig sequence.

Abstract

We demonstrate the use of dynamic decoupling techniques to extend the coherence time of a single memory qubit by nearly two orders of magnitude. By extending the Hahn spin-echo technique to correct for unknown, arbitrary polynomial variations in the qubit precession frequency, we show analytically that the required sequence of pi-pulses is identical to the Uhrig dynamic decoupling (UDD) sequence. We compare UDD and CPMG sequences applied to a single Ca-43 trapped-ion qubit and find that they afford comparable protection in our ambient noise environment.