Abstract
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.
Highlights
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
Using dispersive microwave spectroscopy we resolve the characteristic band dispersion of graphene, and observe coherent electronic interference effects that confirm the ballistic nature of our graphene Josephson junction (JJ)
It consists of four λ/4 coplanar waveguide (CPW) resonators multiplexed to a common feedline
Summary
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 the characteristic band dispersion of graphene, and observe coherent electronic interference effects that confirm the ballistic nature of our graphene JJs. We perform energy level spectroscopy at B|| = 0 T to resolve a linewidth of ≃ 400 MHz. the large linewidths prevent coherent qubit control, we demonstrate the device is insensitive to the applied magnetic field up to B|| = 1 T. techniques. Device B is shaped (Fig. 1c) before a Ti/Au gate stack with a SiNx interlayer is deposited (Fig. 1d)
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