Strong coupling of a superconducting flux qubit to single bismuth donors

TL;DR

This paper demonstrates a protocol where a superconducting flux qubit coherently transfers quantum information from single bismuth donors in silicon, enabling controlled long-distance quantum communication with minimal decoherence.

Contribution

It introduces a novel method for coupling bismuth donor spins to a superconducting flux qubit, acting as a quantum bus for scalable quantum information transfer.

Findings

Successful transfer of quantum information between bismuth donors and flux qubits.

Long coherence times of bismuth donor spins maintained during coupling.

Potential for scalable quantum computing architectures.

Abstract

The realization of a quantum computer represents a tremendous scientific and technological challenge due to the extreme fragility of quantum information. The physical support of information, namely the quantum bit or qubit, must at the same time be strongly coupled to other qubits by gates to compute information, and well decoupled from its environment to keep its quantum behavior. An interesting physical system for realizing such qubits are magnetic impurities in semiconductors, such as bismuth donors in silicon. Indeed, spins associated to bismuth donors can reach an extremely long coherence time -- of the order of seconds. Yet it is extremely difficult to establish and control efficient gates between these spins. Here we demonstrate a protocol where single bismuth donors can coherently transfer their quantum information to a superconducting flux qubit, which acts as a mediator or quantum bus. This superconducting device allows to connect distant spins on-demand with little impact on their coherent behavior.