Electrical properties of Ge spin-3/2 hole qubits


Martedì 3 Ottobre 2023, ore 14.30
Aula Seminari, I piano, U5

Titolo: Electrical properties of Ge spin-3/2 hole qubits
Relatore: prof. Dimi Culcer, The University of New South Wales, Sydney (Australia)

Dimitrie Culcer obtained his PhD from the University of Texas at Austin in 2005. He worked as a postdoctoral research fellow first at Argonne National Laboratory between 2006-2008, and subsequently at the University of Maryland, College Park, 2008-2010. He became a faculty member at the University of Science and Technology of China in Hefei in 2010, where he was a member of the International Center for Quantum Design of Functional Materials. In 2013 he moved to the University of New South Wales in Sydney where he is currently an Associate Professor, and a Chief Investigator in the Australian Research Council Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET). In 2019 he was awarded a Future Fellowship by the Australian Research Council.

Dimi Culcer's research interests include quantum information and computation, spin-orbit coupling and topological effects in condensed matter physics, quantum transport theory and nonlinear electrical and optical effects, with a focus on topological materials. He is actively working in all these areas.

Abstract: Strong spin-orbit interactions make hole quantum dots central to the quest for electrical spin qubit manipulation enabling fast, low-power, scalable quantum computation. Yet it is important to establish to what extent spin-orbit coupling exposes qubits to electrical noise, facilitating decoherence. Here, taking first Ge as an example, I will show that group IV gate-defined hole spin qubits generically exhibit sweet spots, defined by the top gate electric field, at which they are fast and long-lived: the dephasing rate vanishes to first order in electric field noise along all directions in space, the electron dipole spin resonance strength is maximised, while relaxation is drastically reduced at small magnetic fields. The existence of sweet spots is traced to group IV crystal symmetry and properties of the Rashba spin-orbit interaction unique to spin-3/2 systems. I will show that similar findings apply to Si. Our results overturn the conventional wisdom that fast operation implies reduced lifetimes, and suggest group IV hole spin qubits as ideal platforms for ultrafast, highly coherent scalable quantum computing [1].

1. Zhanning Wang, Elizabeth Marcellina, Alex Hamilton, James Cullen, Sven Rogge, Joe Salfi, and Dimi Culcer, NPJ Quantum Information 7, 54 (2021).