QuTech and Kavli Institute for Nanoscience, Delft University of Technology, 2600 GA, Delft, The Netherlands.
Advanced Materials Laboratory, National Institute for Materials Science, 1-1 Namiki, Tsukuba, 305-0044, Japan.
Nat Commun. 2018 Nov 5;9(1):4615. doi: 10.1038/s41467-018-07124-x.
Circuit quantum electrodynamics has proven to be a powerful tool to probe mesoscopic effects in hybrid systems and is used in several quantum computing (QC) proposals that require a transmon qubit able to operate in strong magnetic fields. To address this we integrate monolayer graphene Josephson junctions into microwave frequency superconducting circuits to create graphene based transmons. Using dispersive microwave spectroscopy we resolve graphene's characteristic band dispersion and observe coherent electronic interference effects confirming the ballistic nature of our graphene Josephson junctions. We show that the monoatomic thickness of graphene renders the device insensitive to an applied magnetic field, allowing us to perform energy level spectroscopy of the circuit in a parallel magnetic field of 1 T, an order of magnitude higher than previous studies. These results establish graphene based superconducting circuits as a promising platform for QC and the study of mesoscopic quantum effects that appear in strong magnetic fields.
电路量子电动力学已被证明是探测混合系统中介观效应的有力工具，并被用于几项需要能够在强磁场中工作的超导量子比特的量子计算 (QC) 方案中。为了解决这个问题，我们将单层石墨烯约瑟夫森结集成到微波频率超导电路中，以创建基于石墨烯的超导量子比特。使用色散微波光谱法，我们解析了石墨烯的特征能带色散，并观察到相干电子干涉效应，证实了我们的石墨烯约瑟夫森结的弹道性质。我们表明，石墨烯的单原子厚度使器件对施加的磁场不敏感，这使我们能够在 1 T 的平行磁场中对电路进行能级光谱测量，比以前的研究高一个数量级。这些结果确立了基于石墨烯的超导电路作为 QC 和研究强磁场中出现的介观量子效应的有前途的平台。
