Spin-valley locked excited states spectroscopy in a one-particle bilayer graphene quantum dot

Hadrien Duprez (), Solenn Cances, Andraz Omahen, Michele Masseroni, Max J. Ruckriegel, Christoph Adam, Chuyao Tong, Rebekka Garreis, Jonas D. Gerber, Wister Huang, Lisa Gächter, Kenji Watanabe, Takashi Taniguchi, Thomas Ihn and Klaus Ensslin
Additional contact information
Hadrien Duprez: ETH Zurich
Solenn Cances: ETH Zurich
Andraz Omahen: ETH Zurich
Michele Masseroni: ETH Zurich
Max J. Ruckriegel: ETH Zurich
Christoph Adam: ETH Zurich
Chuyao Tong: ETH Zurich
Rebekka Garreis: ETH Zurich
Jonas D. Gerber: ETH Zurich
Wister Huang: ETH Zurich
Lisa Gächter: ETH Zurich
Kenji Watanabe: National Institute for Materials Science
Takashi Taniguchi: National Institute for Materials Science
Thomas Ihn: ETH Zurich
Klaus Ensslin: ETH Zurich

Nature Communications, 2024, vol. 15, issue 1, 1-7

Abstract: Abstract Current semiconductor qubits rely either on the spin or on the charge degree of freedom to encode quantum information. By contrast, in bilayer graphene the valley degree of freedom, stemming from the crystal lattice symmetry, is a robust quantum number that can therefore be harnessed for this purpose. The simplest implementation of a valley qubit would rely on two states with opposite valleys as in the case of a single-carrier bilayer graphene quantum dot immersed in a small perpendicular magnetic field (B⊥ ≲ 100 mT). However, the single-carrier quantum dot excited states spectrum has not been resolved to date in the relevant magnetic field range. Here, we fill this gap, by measuring the parallel and perpendicular magnetic field dependence of this spectrum with an unprecedented resolution of 4 μeV. We use a time-resolved charge detection technique that gives us access to individual tunnel events. Our results come as a direct verification of the predicted spectrum and establish a new upper-bound on inter-valley mixing, equal to our energy resolution. Our charge detection technique opens the door to measuring the relaxation time of a valley qubit in a single-carrier bilayer graphene quantum dot.

Date: 2024
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DOI: 10.1038/s41467-024-54121-4

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