LN01.02.03 : Gate-Controlled Quantum Dots and Superconductivity in Planar Germanium

3:30 PM–4:00 PM Apr 3, 2018

PCC West, 100 Level, Room 101 AB

David Franke1 Menno Veldhorst1

1, Delft University of Technology, Delft, , Netherlands

Quantum materials exhibit unique properties to study the most fundamental aspects of quantum mechanics. Exploiting these phenomena for future quantum technology will require a materials platform that can combine them with reproducibility, uniformity, and scalability. Silicon germanium heterostructures offer the capability to combine the unparalleled industrial semiconductor technology with key elements of the quantum toolbox, including long quantum coherence, strong spin-orbit coupling, and superconductivity. We present our latest results on gate-defined quantum dots and superconductivity in Ge/SiGe quantum wells [1] and give a perspective on the wide possibilities that this materials system offers in the domain of quantum information.
Because of the abundance of their nuclear-spin-free isotopes, Si and Ge can host spin qubits with long quantum coherence and excellent qubit control, enabling the recent implementation of two-qubit quantum algorithms and strong electron phonon coupling in Si/SiGe devices. While these results are promising, quantum hardware beyond the few qubit regime will need to overcome additional challenges, such as gate connection bottlenecks. Here, an excellent reproducibility and uniformity are key and can enable qubit arrays with shared control [2] using the leverage of today’s semiconductor manufacturing.
Holes in Ge/SiGe heterostructures can provide the necessary high mobility and come with strong spin-orbit coupling for fast qubit operation. As an added bonus, Ge readily forms Ohmic contacts with metal leads which are diffused into the heterostructure. This not only significantly simplifies the fabrication and tuning processes for quantum dot devices, but also enables proximity-induced superconductivity in Ge quantum wells. We present the confinement of heavy holes with mobilities exceeding 500,000 cm2/Vs in quantum dots and find a remarkable uniformity of the gate control. Furthermore, gate-controlled superconductivity is demonstrated in these heterostructures. These first results confirm the great potential of Germanium as a leading material for quantum computing as well as a versatile platform for semiconductor – superconductor hybrids and the exploration of emergent physics.
[1] N.W. Hendrickx, D.P. Franke, A. Sammak, M. Kouwenhoven, D. Sabbagh, L. Yeoh, R. Li, M.L.V. Tagliaferri, M. Virgilio, G. Capellini, G. Scappucci, and M. Veldhorst, preprint at arxiv:1801.08869 (2018)
[2] R. Li, L. Petit, D.P. Franke, J.P. Dehollain, J. Helsen, M. Steudtner, N.K. Thomas, Z.R. Yoscovits, K.J. Singh, S. Wehner, L.M.K. Vandersypen, J.S. Clarke, and M. Veldhorst, preprint at arxiv:1711.03807 (2017)