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Concentric transmon qubit featuring fast tunability and an anisotropic magnetic dipole moment



Jochen Braumuller, Martin O. Sandberg, Michael Vissers, Andre Schneider, Steffen Schlor, Lukas Grunhaupt, Hannes Rotzinger, Michael Marthaler, Alexander Lukashenko, Amadeus Dieter, Alexey V. Ustinov, Martin Weides, David P. Pappas


We present a planar qubit design based on a superconducting circuit that we call concentric transmon. While employing a straightforward fabrication process using Al evaporation and lift-off lithography, we observe qubit lifetimes and coherence times in the order of 10 μs. We systematically characterize loss channels such as incoherent dielectric loss, Purcell decay and radiative losses. The implementation of a gradiometric SQUID loop allows for a fast tuning of the qubit transition frequency and therefore for full tomographic control of the quantum circuit. Due to the large loop size, the presented qubit architecture features a strongly increased magnetic dipole moment as compared to conventional transmon designs. This renders the concentric transmon a promising candidate to establish a site-selective passive direct Ẑ coupling between neighboring qubits, being a pending quest in the field of quantum simulation.
Applied Physics Letters


planar qubit design, superconducting circuit, concentric transmon, Al evaporation, lift-off lithography, qubit lifetimes, coherence times, incoherent dielectric loss, qubit transition frequency, gradiometric SQUID loop, tomographic control, magnetic dipole moment, site-selective passive


Braumuller, J. , Sandberg, M. , Vissers, M. , Schneider, A. , Schlor, S. , Grunhaupt, L. , Rotzinger, H. , Marthaler, M. , Lukashenko, A. , Dieter, A. , Ustinov, A. , Weides, M. and Pappas, D. (2016), Concentric transmon qubit featuring fast tunability and an anisotropic magnetic dipole moment, Applied Physics Letters, [online], (Accessed April 20, 2024)
Created January 20, 2016, Updated October 12, 2021