A Ge heavy hole spin qubit

The interest in hole spins as potential qubits has strongly increased in the past few years. Due to the intrinsically large spin orbit coupling, hole spin qubits should be electrically tunable and show high Rabi frequencies. Indeed in 2016, the first electrically tunable hole spin qubit with Rabi frequencies as high as 70MHz was demonstrated [1]. In our group we work with Ge. Results on the first Ge hole spin qubit will be presented. The qubit is formed in a Ge hut wire [2] double quantum dot. Rabi-frequencies of 140 MHz were reached [3] and Ramsey experiments revealed dephasing times T2* exceeding 130 ns. Furthermore, by measuring the spin relaxation time of holes in Ge hut wires an upper bound for the coherence time could be extracted [4]. While these experiments underline the potential of hole spins in Ge, randomly grown nanowires are not very appealing for the creation of more complex qubit devices. Latest results on positioned hut wires which emphasize the potential of this material platform for scalable quantum devices will be presented.

[1] R. Maurand et al., Nature Communications 7, 13575 (2016).
[2] J. J. Zhang et al., Phys. Rev. Lett. 109, 085502 (2012).
[3] H. Watzinger, J. Kukucka et al., Nature Communications 9, 3902 (2018).
[4] L. Vukušić et al., arXiv:1803.01775.