Extending Quantum Coherence in Diamond

TL;DR

This paper demonstrates a significant extension of quantum coherence times in diamond nitrogen vacancy centers using decoupling techniques, achieving over 1.6 milliseconds of coherence in natural diamond.

Contribution

The study shows that simple equal pulse spacing decoupling performs as well as Uhrig decoupling and enables longer coherence times by exploiting echo revivals.

Findings

Coherence time extended from 2.7 microseconds to over 340 microseconds.

Pulse phase optimization compensates for pulse imperfections across all states.

Achieved coherence times exceeding 1.6 milliseconds in natural diamond.

Abstract

We experimentally demonstrate over two orders of magnitude increase in the coherence time of nitrogen vacancy centres in diamond by implementing decoupling techniques. We show that equal pulse spacing decoupling performs just as well as non-periodic Uhrig decoupling and has the additional benefit that it allows us to take advantage of "revivals" in the echo (due to the coherent nature of the bath) to explore the longest coherence times. At short times, we can extend the coherence of particular quantum states out from T_2*=2.7 us out to an effective T_2 > 340 us. For preserving arbitrary states we show the experimental importance of using pulse sequences, that through judicious choice of the phase of the pulses, compensate the imperfections of individual pulses for all input states. At longer times we use these compensated sequences to enhance the echo revivals and show a coherence time of over 1.6 ms in ultra-pure natural abundance 13C diamond.