# Scalable quantum computer with superconducting circuits in the ultrastrong coupling regime

## TL;DR

This paper proposes a scalable superconducting quantum computing architecture that uses ultrastrong coupling in a quantum bus to enable fast, switchable interactions between distant qubits, overcoming connectivity limitations.

## Contribution

It introduces a novel architecture employing ultrastrong coupling in flux qubits to enhance qubit interactions and scalability in superconducting quantum computers.

## Key findings

- Enables simultaneous distant qubit coupling via a dispersive quantum bus.
- Achieves quantum gates on nanosecond timescales.
- Maintains qubit coherence during interactions.

## Abstract

So far, superconducting quantum computers have certain constraints on qubit connectivity, such as nearest-neighbor couplings. To overcome this limitation, we propose a scalable architecture to simultaneously connect several pairs of distant qubits via a dispersively coupled quantum bus. The building-block of the bus is composed of orthogonal coplanar waveguide resonators connected through ancillary flux qubits working in the ultrastrong coupling regime. This regime activates virtual processes that boost the effective qubit-qubit interaction, which results in quantum gates on the nanosecond timescale. The interaction is switchable and preserves the coherence of the qubits.