Superconducting tetrahedral quantum bits

TL;DR

This paper introduces a novel superconducting tetrahedral qubit design that offers enhanced noise resistance, degeneracy, and flexible manipulation, advancing quantum computing hardware.

Contribution

It presents a new tetrahedral superconducting qubit architecture with noise immunity and tunable degeneracy, supported by spectral analysis and numerical validation.

Findings

Degenerate ground state minimizes decoherence

Weak quadratic noise sensitivity due to symmetry

Effective manipulation and measurement schemes

Abstract

We propose a new design for a quantum bit with four superconducting islands in the topology of a symmetric tetrahedron, uniformly frustrated with one-half flux-quantum per loop and one-half Cooper-pair per island. This structure emulates a noise-resistant spin-1/2 system in a vanishing magnetic field. The tetrahedral quantum bit combines a number of advances such as a doubly degeneracy ground state minimizing decoherence via phonon radiation, a weak quadratic sensitivity to electric and magnetic noise, relieved constraints on the junction fabrication, a large freedom in manipulation, and attractive measurement schemes. The simultaneous appearance of a degenerate ground state and a weak noise sensitivity are consequences of the tetrahedral symmetry, while enhanced quantum fluctuations derive from the special magnetic frustration. We determine the spectral properties of the tetrahedral structure within a semiclassical analysis and confirm the results numerically. We show how proper tuning of the charge-frustration selects a doubly degenerate ground state and discuss the qubit's manipulation through capacitive and inductive coupling to external bias sources. The complete readout of all the spin-components is achieved through coupling of the internal qubit currents to external junctions driven close to criticality during the measurement.