# Pseudo-2D superconducting quantum computing circuit for the surface code: the proposal and preliminary tests

## TL;DR

This paper proposes a novel pseudo-2D superconducting quantum circuit architecture that eliminates the need for complex 3D wiring, enabling scalable, planar quantum computing with high fidelity and minimal cross-talk.

## Contribution

Introduction of a pseudo-2D resonator network with airbridges for inter-qubit connections, simplifying wiring and enhancing scalability in superconducting quantum computers.

## Key findings

- Airbridge resonators have sufficient quality factor for high fidelity gates.
- The design reduces cross-talk and decoherence in large-scale chips.
- The architecture enables monolithic integration without additional packaging complexity.

## Abstract

Of the many potential hardware platforms, superconducting quantum circuits have become the leading contender for constructing a scalable quantum computing system. All current architecture designs necessitate a 2D arrangement of superconducting qubits with nearest neighbour interactions, compatible with powerful quantum error correction using the surface code. A major hurdle for scalability in superconducting systems is the so called wiring problem, where qubits internal to a chip-set become inaccessible for external control/readout lines. Current approaches resort to intricate and exotic 3D wiring and packaging technology which is a significant engineering challenge to realize, while maintaining qubit fidelity. Here we solve this problem and present a modified superconducting scalable micro-architecture that does not require any 3D external line technology and reverts back to a completely planar design. This is enabled by a new pseudo-2D resonator network that provides inter-qubit connections via airbridges. We carried out experiments to examine the feasibility of the newly introduced airbridge component. The measured quality factor of these new inter-qubit resonators is sufficient for high fidelity gates, below the threshold for the surface code, with negligible measured cross-talk. The resulting physical separation of the external wirings and the inter-qubit connections on-chip should reduce cross-talk and decoherence as the chip-set increases in size. This result demonstrates that a large-scale, fully error corrected quantum computer can be constructed by monolithic integration technologies without additional overhead and without special packaging know-hows.