Two-electron states spotted in bilayer graphene quantum dots useful for qubits

Researchers at the Laboratory for Solid State Physics at ETH Zürich and the National Institute for Materials Science in Japan created bilayer graphene quantum dots, confining electrons to a space small enough to exhibit both long-lived spin and valley states. The work reports on spectroscopy of these few-carrier states using circuit quantum electrodynamics, a technique offering improved energy resolution compared to standard methods. Measurements reveal dispersive features of two- and three-electron states, enabling detection of Pauli spin and valley blockade, and characterization of the spin-orbit gap at zero magnetic field, consistently measured to be approximately 1.5 meV. The results deepen understanding of these confined electronic systems, crucial for implementing solid-state qubits…