Long-range tunable coupler for modular fluxonium quantum processors

TL;DR

This paper introduces a long-range tunable coupler for fluxonium qubits, enabling modular quantum processors with high-fidelity, low-error inter-module gates over distances exceeding one centimeter.

Contribution

It proposes a novel coupler design that supports scalable, long-range interconnects for fluxonium qubits, facilitating modular quantum computing architectures.

Findings

Potential to achieve sub-100-ns two-qubit gates with errors below 10^-4

Supports inter-module coupling over distances greater than one centimeter

Enables modular fluxonium quantum processors with low crosstalk

Abstract

The path toward practical superconducting quantum processors requires the integration of a large number of high-performance qubits. Modular architectures could offer a way to address the scaling limitations of monolithic designs by partitioning a large quantum processor into physically separated modules, or chiplets, linked through long-range interconnects. In this context, although fluxonium qubits have emerged as a compelling platform for quantum computing due to their long coherence times and high-fidelity gates, existing coupling schemes remain restricted to qubits in close proximity on a single chip. This limitation inherently precludes the long-range interconnects essential for modular integration. In this work, we propose a long-range tunable coupler designed to interconnect fluxonium qubits separated by more than one centimeter, thereby supporting the realization of modular fluxonium quantum processors. Under realistic assumptions, the proposed coupler has the potential to achieve inter-module two-qubit gate performance, specifically sub-100-ns gates with intrinsic errors below $10^{-4}$, comparable to that of intra-module (intra-chiplet) gates, while enabling modular integration with low quantum crosstalk, a key requirement for scalable systems. We further discuss the integration of this coupler into modular fluxonium lattices and explore its feasibility for achieving the higher connectivity and longer coupling range required for complex quantum error correction codes. This work could contribute to the development of large-scale fluxonium quantum processors by bridging their demonstrated potential with modular scalability.