A. Tarascio1, S. Svab1, O. Sharifi1, L. C. Camenzind1, T. Patlatiuk1, P. Scarlino2, D. M. Zumbühl1
1Department of Physics, University of Basel, Switzerland
2Department of Physics, Ecole Polytechnique Federal de Lausanne, Switzerland
One of the grand challenges of quantum computing is achieving good connectivity as required for scaling-up. The goal of this project is to couple semiconductor qubits via a quantum bus based on Surface Acoustic Waves (SAWs). The interaction between the qubit and the SAW phonons follow the same formalism of the Jaynes-Cummings model used cavity QED and circuit QED, suggesting that it’s possible to realize analogous experiments. Unlike the majority of photonic resonators, SAW resonators can operate in strong magnetic fields and up to high temperatures without significant loss of quality.
It has been shown that SAW resonators have quality factors exceeding 100,000 at 4K. SAW phonons have a different phase velocity than bulk phonons. This means that they cannot phase match to any bulk wave, resulting in high Q. 
As a proof of concept for the SAW quantum bus the substrate chosen is GaAs, since it is piezoelectric, thus allowing fabrication of SAW resonators using well established lithography. Moreover, GaAs heterostructures have very high mobility 2DEGs. The nuclear spin bath of GaAs limits the coherence of spin qubits but it should still be possible to observe SAW-spin strong coupling.
Once that the fundamental mechanism is investigated we imagine that this technique could be implemented on other non-piezoelectric substrates such as Si using thin films, and eventually allowing for highly scalable qubit networks.
Funding Acknowledgement: Supported by the Swiss National Science Foundation (SNSF), the Swiss Nanoscience Institute (SNI), and the European Microkelvin Platform (EMP).
 Schütz, M. J. (2017). Universal quantum transducers based on surface acoustic waves. In Quantum Dots for Quantum Information Processing: Controlling and Exploiting the Quantum Dot Environment (pp. 143-196). Springer, Cham.