Proposal for erasure conversion in integer fluxonium qubits

TL;DR

This paper proposes an erasure conversion scheme for integer fluxonium qubits that enhances coherence times by detecting and mitigating dominant energy relaxation errors, improving quantum error correction.

Contribution

It introduces a novel erasure conversion protocol for fluxonium qubits that leverages their noise insensitivity and symmetry properties to improve quantum coherence.

Findings

Erasure errors can be efficiently detected using dispersive readout.

Proper circuit design and gate sets enhance effective coherence times.

The scheme significantly improves quantum error correction performance.

Abstract

We propose an erasure conversion scheme on the $|e\rangle-|f\rangle$ and $|g\rangle-|f\rangle$ qubits in integer fluxonium qubits (IFQs), which are both first-order insensitive to $1/f$ flux noise. The $|e\rangle-|f\rangle$ transition is identical to that of a usual fluxonium qubit and hence is expected to have excellent coherence time, while the $|g\rangle-|f\rangle$ transition is additionally protected from the energy relaxation by the parity symmetry. The dominant error in both qubits arises due to the energy relaxation: from $|e\rangle$ to $|g\rangle$ in the $e\text{--}f$ qubit and from $|f\rangle$ to $|e\rangle$ in the $g\text{--}f$ qubit. Such errors can be treated as erasure events, and their efficient detection improves the performance of quantum error-correcting codes. We consider a protocol for such erasure conversion based on the dispersive readout. Our main finding is that, with proper circuit parameter choice, carefully designed gate sets, and the integration of erasure conversion, IFQs promise high effective coherence times.