Flux-Tunable Regimes and Supersymmetry in Twisted Cuprate Heterostructures

TL;DR

This paper explores flux-tunable regimes and supersymmetry in twisted cuprate heterostructures, demonstrating protected qubits and artificial atoms in Josephson junctions with potential applications in quantum computing.

Contribution

It introduces a novel flux-tunable Josephson junction system in twisted cuprates that exhibits protected qubit regimes and supersymmetric quantum circuits.

Findings

Flowermon qubit regime is maintained up to a critical magnetic field.

The system can be protected against charge and flux noise.

Implementation of artificial atoms and supersymmetric circuits is demonstrated.

Abstract

Van der Waals assembly allows for the creation of Josephson junctions in an atomically sharp interface between two exfoliated Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (Bi-2212) flakes that are twisted relative to each other. In a narrow range of angles close to $45^\circ$, the junction exhibits a regime where time-reversal symmetry can be spontaneously broken and it can be used to encode an inherently protected qubit called flowermon. In this work we investigate the physics emerging when two such junctions are integrated in a SQuID circuit threaded by a magnetic flux. We show that the flowermon qubit regime is maintained up to a finite critical value of the magnetic field and, under appropriate conditions, it is protected against both charge and flux noise. For larger external fluxes, the interplay between the inherent twisted d-wave nature of the order parameter and the external magnetic flux enables the implementation of different artificial atoms, including a flux-biased protected qubit and a supersymmetric quantum circuit.