Berlin 2024 – scientific programme

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QI: Fachverband Quanteninformation

QI 2: Semiconductor Qubits (joint session QI/HL)

QI 2.4: Invited Talk

Monday, March 18, 2024, 10:30–11:00, HFT-FT 131

Gate defined electron and hole quantum dots in bilayer graphene — •Luca Banszerus — Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark — JARA-FIT and 2nd Institute of Physics A, RWTH Aachen University, Aachen, Germany

Bilayer graphene (BLG) quantum dots (QDs) have long been regarded as an attractive platform for hosting spin qubits since the low nuclear spin densities and weak spin-orbit interaction in BLG promise long spin coherence times. In addition to the spin, BLG exhibits a tunable valley degree of freedom, which is associated with a strong out-of-plane magnetic moment with opposite signs for the K- and K'-valley. This allows controlling the valley splitting in BLG and to use valley space as an additional qubit platform.

In contrast to conventional semiconductors, the band structure of BLG is (almost) perfectly electron/hole symmetric and exhibits an electrically tuneable band gap, which we use to form ambipolar electron/hole double QDs. We observe the creation of single electron-hole pairs with opposite quantum numbers and use the electron-hole symmetry to achieve a protected spin-valley blockade in electron-hole double quantum dots. The latter allows for spin-to-charge conversion and valley-to-charge conversion, which is essential for the operation of spin and valley qubits.

Keywords: Bilayer Graphene; Quantum Dot; Pauli Blockade; Spin