Ultra-long relaxation of a Kramers qubit formed in a bilayer graphene quantum dot

• DOI: 10.48550/arxiv.2403.08143
• Publication Date: 2024-03-12
• Authors: Artem O. Denisov; Veronika Reckova; Solenn Cances; Max J. Ruckriegel; Michele Masseroni; Christoph Adam; Chuyao Tong; Jonas Daniel Gerber; W. Huang; Kenji Watanabe; Takashi Taniguchi; Thomas Ihn; K. Ensslin; Hadrien Duprez
• Keywords: Bilayer graphene

The intrinsic valley degree of freedom makes bilayer graphene a unique platform for emerging types semiconducting qubits. single-carrier quantum dot ground state exhibits two-fold degeneracy where the two states have opposite spin and numbers. By breaking time-reversal symmetry this with an out-of-plane magnetic field, novel type qubit (Kramers qubit), encoded in two-dimensional spin-valley subspace, becomes accessible. Kramers is robust against known spin- valley-mixing mechanisms, as it requires simultaneous change both numbers, potentially resulting long relaxation coherence times. We measure time single carrier excited at small ($\sim \mathrm{mT}$) zero fields. demonstrate ultra-long times exceeding $30~\mathrm{s}$, which about orders magnitude longer than $400~\mathrm{ms}$. demonstrated high-fidelity single-shot readout are foundation novel, long-lived semiconductor