Modular tunable coupler for superconducting qubits

TL;DR

This paper introduces a modular, tunable double-transmon coupler for superconducting qubits that enables fast, high-fidelity quantum operations with an internally controlled zero-coupling state, enhancing scalability.

Contribution

The paper presents a novel double-transmon coupler architecture with flux-controlled interference and an internal zero-coupling state, improving modularity and robustness in quantum circuits.

Findings

Achieves tunable coupling via flux-controlled interference.

Features an internally-defined zero-coupling state independent of qubits.

Suitable for high-fidelity two-qubit gates and quantum bus interfaces.

Abstract

The development of modular and versatile quantum interconnect hardware is a key next step in the scaling of quantum information platforms to larger size and greater functionality. For superconducting quantum systems, fast and well-controlled tunable circuit couplers will be paramount for achieving high fidelity and resource efficient connectivity, whether for performing two-qubit gate operations, encoding or decoding a quantum data bus, or interfacing across modalities. Here we propose a versatile and internally-tunable double-transmon coupler (DTC) architecture that implements tunable coupling via flux-controlled interference in a three-junction dcSQUID. Crucially, the DTC possesses an internally defined zero-coupling state that is independent of the coupled data qubits or circuit resonators. This makes it particular attractive as a modular and versatile design element for realizing fast and robust linear coupling in several applications such as high-fidelity two-qubit gate operations, qubit readout, and quantum bus interfacing.