QDev Seminar: Marco Tagliaferri – University of Copenhagen

QDev Seminar: Marco Tagliaferri

QuTech, TU Delft and Kavli Institute of Nanoscience, Delft, The Netherlands

Spin-qubits in group-IV semiconductors: Challenges and opportunities in Si and Ge

Following the seminal proposal of Loss and Di Vincenzo [1], impressive results have been obtained with spin qubits based on quantum dots. The long coherence times obtained by isotopic purification and the fabrication processes compatible with industrial standards made them good candidate for large-scale computation.
In silicon, recent experiments have shown the building blocks for fault- tolerant quantum computation and proposals of scalable quantum dots arrays have been presented [2]. Here I will show that the high fidelity readout required for fault tolerant operations is possible even in presence of the valley degree of freedom [3]. Indeed the tunability of the valley splitting typical of Si-MOS devices allows qubit operation in the few kelvin regime, enabling to co-integrate on-chip quantum and classical electronic for improved scalability.
On the other hand, recent experiments showing high mobility in germanium heterostructures have led to a revival of germanium as host material for quantum computation [5]. The possible advantages range from all electrical control to semiconductor/superconductor hybrid in the same platform usable as long-range couplers. In the final part of my talk I will review recent experiments on proximity-induced superconduction in Ge-Josephson junctions.

[1] D. Loss et al., Phys. Rev. A, 57, 120 (1998);

[2] T. Watson et al., Nature, 555, 633 (2018); R. Li et al., Sci. Adv., 4, 3960 (2018); N. Samkharadze et al., Science, 359, 1123 (2018);

[3] M.Tagliaferri et al., Phys. Rev. B, 97, 245412 (2018);

[4] L. Petit et al., arXiv: 1803.01774 (2018);

[5] N. Hendickx et al., Nature Comm., 9, 2835 (2018).