Low crosstalk modular flip-chip architecture for coupled superconducting qubits

TL;DR

This paper introduces a modular flip-chip architecture for superconducting qubits that reduces crosstalk and simplifies assembly, validated with a chain of flux qubits demonstrating high on/off coupling ratio and minimal crosstalk.

Contribution

The paper presents a novel electrically floating flip-chip design for superconducting qubits, enhancing modularity and reducing crosstalk compared to existing approaches.

Findings

Achieved a coupling on/off ratio of approximately 50.

Measured zz-crosstalk of about 0.7 kHz between resonant qubits.

Demonstrated isolation between qubit enclosures exceeding 60 dB.

Abstract

We present a flip-chip architecture for an array of coupled superconducting qubits, in which circuit components reside inside individual microwave enclosures. In contrast to other flip-chip approaches, the qubit chips in our architecture are electrically floating, which guarantees a simple, fully modular assembly of capacitively coupled circuit components such as qubit, control, and coupling structures, as well as reduced crosstalk between the components. We validate the concept with a chain of three nearest neighbor coupled generalized flux qubits in which the center qubit acts as a frequency-tunable coupler. Using this coupler, we demonstrate a transverse coupling on/off ratio $\approx$ 50, zz-crosstalk $\approx$ 0.7 kHz between resonant qubits and isolation between the qubit enclosures > 60 dB.