Strong coupling of a superconducting flux qubit to single bismuth donors

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 behaviour. 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 distant spins. Here we demonstrate a protocol where single bismuth donors can coherently transfer their quantum information to a superconducting flux qubit, which may act as a mediator or quantum bus. This superconducting device allows to connect distant spins on-demand without compromising their coherent behaviour. 

References 

[1] M. Stern et al., Phys. Rev. Lett. 113, 123601 (2014). 

[2] T. Douce et al., Phys. Rev. A, 92, 052335 (2015). 

[3] A. Bienfait et al., Nature Nanotechnology, 282,1038 (2015). 

[4] T. Chang et al., Phys. Rev. Appl., 18, 064062 (2022). 

[5] T. Chang et al., Phys. Rev. Appl., 19, 024066 (2023).