Circuit QED with a graphene double quantum dot and a reflection-line resonator

Graphene has attracted considerable attention in recent years due to its unique physical properties and potential applications. Graphene quantum dots have been proposed as quantum bits, and their excited-state relaxation rates have been studied experimentally. However, their dephasing rates remain unexplored. In addition, it is still not clear how to implement long-range interaction among qubits for future scalable graphene quantum computing architectures. Here we report a circuit quantum electrodynamics (cQED) experiment using a graphene double quantum dot (DQD) charge qubit and a superconducting reflection-line resonator (RLR). The demonstration of this capacitive coupling between a graphene qubit and a resonator provides a possible approach for mediating interactions between spatially-separated graphene qubits. Furthermore, taking advantage of sensitive microwave readout measurements using the resonator, we measure the charge-state dephasing rates in our hybrid graphene nanostructure, which is found to be of the order of GHz. A spectral analysis method is also developed to simultaneously extract: the DQD-resonator coupling strength, the tunneling rate between the DQD charge states, and the charge-state dephasing rate. Our results show that this graphene cQED architecture can be a compelling platform for both graphene physics research and potential applications.