Self-consistent Noise Characterization of Quantum Devices

Won Kyu Calvin Sun | Paola Cappellaro

The power of quantum devices is limited by decoherence. The most accurate understanding of decoherence, requiring a full quantum-mechanical treatment of the system and (unknown) bath, is not only nontrivial in theory but also prohibitive in practice with increasing system size. Therefore, a noise model of decoherence that is both practical (i.e., classical) and predictive is desired, not only as a tool to characterize unknown (quantum) baths of interest (e.g., for quantum sensing or device characterization), but also to develop more robust quantum devices. While a classical noise model for a qubit under a fixed dynamics is known to be always possible, it is not guaranteed to be predictive for any different dynamics. To address this problem, we first propose a protocol to build a classical noise model of qubit decoherence that is self-consistent with a varied set of dynamics. If such a model is possible, it simultaneously characterizes the bath and is expected to be predictive under new dynamics; however, if it is not possible, it directly heralds a more complex, possibly quantum, bath that may be of interest for further investigation. Applying this protocol, we characterize the noise affecting our quantum device of interest, a nanoscale register of two electronic spins in diamond

Funding Sources: No.PHY1415345 | No. EECS1702716