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

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.

11 pages, 7 figures

References in corpus (6)

• Charge insensitive qubit design derived from the Cooper pair box
• Resolving photon number states in a superconducting circuit
• Superconducting qubit in waveguide cavity with coherence time approaching 0.1ms
• Implementation of low-loss superinductances for quantum circuits
• Quantum Superinductor with Tunable Non-Linearity
• Moving beyond the transmon: Noise-protected superconducting quantum circuits

Cited by in corpus (19)

• Scalable High-Performance Fluxonium Quantum Processor
• High-Energy Collision of Quarks and Mesons in the Schwinger Model: From Tensor Networks to Circuit QED
• Gralmonium: Granular Aluminum Nano-Junction Fluxonium Qubit
• Unimon qubit
• Fast high-fidelity gates for galvanically-coupled fluxonium qubits using strong flux modulation
• Consistent Quantization of Nearly Singular Superconducting Circuits
• Multi-mode architectures for noise-resilient superconducting qubits
• A superconducting qubit with noise-insensitive plasmon levels and decay-protected fluxon states
• Demonstration of dual Shapiro steps in small Josephson junctions
• Superconducting Levitated Detector of Gravitational Waves
• The quartic Blochnium: an anharmonic quasicharge superconducting qubit
• Bound states in the continuum in a fluxonium qutrit
• Parameter optimization for the unimon qubit
• Local bistability under microwave heating for spatially mapping disordered superconductors
• Circuit Quantisation from First Principles
• Spectral signature of high-order photon processes enhanced by Cooper-pair pairing
• Ultrastrong capacitive coupling of flux qubits
• Localized quasiparticles in a fluxonium with quasi-two-dimensional amorphous kinetic inductors
• High Impedance Granular Aluminum Ring Resonators