Enhancement of quantum coherence in solid-state qubits via interface engineering
Wing Ki Lo, Yaowen Zhang, H. Chow, Jiahao Wu, Man Yin Leung, Kin On Ho, Xuliang Du, Yi‐Fan Chen, Yang Shen, Ding Pan, Sen Yang
Abstract
Shallow nitrogen-vacancy (NV) centers in diamond are promising quantum sensors but suffer from noise-induced short coherence times due to bulk and surface impurities. We present interfacial engineering via oxygen termination and graphene patching, extending shallow NV coherence to over 1 ms, approaching the T1 limit. Raman spectroscopy and density-functional theory reveal surface termination-driven graphene charge transfer reduces spin noise by pairing surface electrons, supported by double electron-electron resonance spectroscopy showing fewer unpaired spins. Enhanced sensitivity enables detection of single weakly coupled 13C nuclear spins and external 11B spins from a hexagonal boron nitride (h-BN) layer, achieving nanoscale nuclear magnetic resonance. A protective h-BN top layer stabilizes the platform, ensuring robustness against harsh treatments and compatibility with target materials. This integrated approach advances practical quantum sensing by combining extended coherence, improved sensitivity, and device durability. Shallow NV centers in diamond are promising quantum sensors but suffer from reduced coherence times due to surface spin impurities. Here the authors improve coherence times to over 1 ms through interface engineering by oxygen-terminating the diamond surface and patching it with graphene.