Locking of electron spin coherence above 20 ms in natural silicon carbide

Abstract

One of the challenges in quantum information science is to achieve ultralong spin coherence in naturally grown solid-state systems. So far, isotope engineering is generally needed to suppress the main relaxation mechanism caused by the interaction with nuclear spins. The authors demonstrate here that this ambitious goal can be achieved in binary compounds with natural isotope abundance too. They attain a spin-locked subspace with a drastically reduced spin-decoherence rate through the combination of two effects. First, the suppression of heteronuclear spin cross-talk is achieved by applying a moderate magnetic field. This leads to two dilute and weakly interacting spin baths. Second, because the interaction between nuclei becomes weak, the mutual spin flip-flop processes occur at lower rate, which can be viewed as a reduction of the high-frequency part of the noise spectrum. As a result, dynamic decoupling protocols demonstrate high performance. Using this approach, the authors are able to preserve a coherent spin superposition above 20 ms, which is an improvement by more than one order of magnitude compared to the earlier reported value in SiC.