Dipole coupling of a bilayer graphene quantum dot to a high-impedance microwave resonator

In this work, we probe quantum dots in bilayer graphene by means of hybrid circuit quantum electrodynamics (circuit QED). The presented circuit QED architecture combines high-impedance microwave resonators with quantum dots electrostatically defined in a graphene-based van der Waals heterostructure [1].

Bilayer graphene is a rapidly developing material system for spin and valley qubits. Electrostatically defined quantum dots in bilayer graphene have successfully demonstrated time-resolved charge detection [2], switchable Pauli spin and valley blockade [3] and long-lived spin and valley states [4], critical prerequisites for a material platform to host spin or valley qubits.

We show results from a high-impedance resonator coupled to a bilayer graphene double quantum dot. Dipole coupling allows the resonator to sense the electric susceptibility of the double quantum dot from which we can reconstruct its charge stability diagram. The charge-photon interaction is quantified in the dispersive and resonant regimes by comparing the coupling-induced change in resonator response to input-output theory. Our results introduce a versatile circuit QED architecture to probe quantum dots in van der Waals materials. We highlight the technical challenges and indicate a path towards coherent charge-photon coupling with bilayer graphene quantum dots.



[1] Ruckriegel, M. J. et al. Electric Dipole Coupling of a Bilayer Graphene Quantum Dot to a High-Impedance Microwave Resonator. Nano Lett. 2024, 24, 24, 7508–7514, DOI: 10.1021/acs.nanolett.4c01791

[2] Gächter, L. M. et al. Single-Shot Spin Readout in Graphene Quantum Dots. PRX Quantum 2022, 3, 020343, DOI: 10.1103/PRXQuantum.3.020343

[3] Tong, C. et al. Pauli Blockade of Tunable Two-Electron Spin and Valley States in Graphene Quantum Dots. Phys. Rev. Lett. 2022, 128, 067702, DOI: 10.1103/PhysRevLett.128.067702

[4] Denisov, A. O. et al. Ultra-long relaxation of a Kramers qubit formed in a bilayer graphene quantum dot. arXiv Preprint , arXiv:2403.08143, 2024. DOI: 10.48550/arXiv.2403.08143