QDev Seminar: Giorgos Katsaros

Institute of Science and Technology Austria

Holes: a blessing or a curse?

In the past 10 years many groups have used electrons confined in silicon quantum dots in order to realize spin qubits [1]. Impressive progress in the extension of spin lifetimes has been achieved and record coherence times of about 1 second were reported in 2014 for 31P electrons in isotopically engineered 28Si substrates [2]. Holes on the other hand are much less studied [3]. Theory predicts that holes can show similar spin lifetimes as electrons [4] and should be promising for creating long distance two qubit gates [5]. However none of these predictions have been verified so far.

In this talk I will focus on holes confined in Ge self-assembled quantum dots. I will present our recent results which demonstrate the presence of purely heavy-hole states in ultra-thin Ge hut wires and discuss our progress in the realization of T-junction charge sensors and double quantum dot devices.

[1] F. A. Zwanenburg et al., Rev. Mod. Phys. 85, 961 (2013)
[2] J. T. Muhonen et al., Nature Nanotechnology 9, 986 (2014)
[3] Y. Hu et al., Nat. Nanotechn. 7, 47 (2012) ; A. P. Higginbotham et al., Nano Letters 14, 3582 (2014)
[4] D. V. Bulaev et al., Phys. Rev. Lett. 95, 076805 (2005)
[5] S. E. Nigg et al., Phys. Rev. Lett. 118, 147701 (2017)
[6] H. Watzinger et al. Nano Letters 16, 6879 (2016)