Mónica Benito, from the Institute of Quantum Technologies, German Aerospace Center (DLR), Ulm, will give a seminar entitled «Hole spin qubits in elongated quantum dots».
Date: March 9th, 2022, 11:00 h.
Location: Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)
Abstract: Rapid development has positioned quantum wells in planar germanium heterostructures at the head of semiconductor quantum dot platforms for quantum information processing [1,2]. We find nuclear-spin-free isotopes, low charge noise and low disorder. The focus is on hole states, due to the absence of valley states, a technically advantageous low effective mass, and the strong spin-orbit coupling that allows for all-electric operation. These works employ heavy-hole spin qubits, which constitute the ground states in these planar devices. Theory predicts an even more promising future for germanium and/or silicon based quantum dots fabricated in nanowires, based on tunable and even stronger spin-orbit coupling relying on the high degree of heavy-light hole mixtures . I will present recent theoretical efforts to understand and experimentally identify the low-energy physics of hole germanium nanowires, including the effect of orbital effects of the magnetic field . We predict optimal qubit operation at a sweet spot with Rabi frequencies in the GHz regime. We find that they can present strong and tunable spin-orbit coupling if the confinement potential is properly squeezed . This confinement-induced spin-orbit coupling, and therefore the qubit-resonator coupling, could be turned on and off, overcoming present scalability challenges.
 Hendrickx et al., Nature 591, 580 (2021)
 F. van Riggelen, et al., arXiv:2202.11530
 C. Kloeffel, et al., Phys. Rev. B 84, 195314 (2011)
 C. Adelsberger, M. Benito, S. Bosco, J. Klinovaja, and D. Loss, PRB 105, 075308 (2022)
 S. Bosco, M. Benito, C. Adelsberger, and D. Loss, PRB 104, 115425 (2021)