Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction

• URL: http://arxiv.org/abs/2106.05882v1
• Date: Thu, 10 Jun 2021 16:09:36 GMT
• Title: Geometric superinductance qubits: Controlling phase delocalization across a single Josephson junction
• Authors: Matilda Peruzzo, Farid Hassani, Gregory Szep, Andrea Trioni, Elena Redchenko, Martin \v{Z}emli\v{c}ka, Johannes Fink
• Abstract summary: We present a large variety of qubits all stemming from the same circuit but with drastically different characteristic energy scales. The use of a geometric inductor results in high precision of the inductive and capacitive energy as guaranteed by top-down lithography.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: There are two elementary superconducting qubit types that derive directly from the quantum harmonic oscillator. In one the inductor is replaced by a nonlinear Josephson junction to realize the widely used charge qubits with a compact phase variable and a discrete charge wavefunction. In the other the junction is added in parallel, which gives rise to an extended phase variable, continuous wavefunctions and a rich energy level structure due to the loop topology. While the corresponding rf-SQUID Hamiltonian was introduced as a quadratic, quasi-1D potential approximation to describe the fluxonium qubit implemented with long Josephson junction arrays, in this work we implement it directly using a linear superinductor formed by a single uninterrupted aluminum wire. We present a large variety of qubits all stemming from the same circuit but with drastically different characteristic energy scales. This includes flux and fluxonium qubits but also the recently introduced quasi-charge qubit with strongly enhanced zero point phase fluctuations and a heavily suppressed flux dispersion. The use of a geometric inductor results in high precision of the inductive and capacitive energy as guaranteed by top-down lithography - a key ingredient for intrinsically protected superconducting qubits. The geometric fluxonium also exhibits a large magnetic dipole, which renders it an interesting new candidate for quantum sensing applications.

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