Progress towards coupling two electron-on-solid-neon qubits in the strong-dispersive regime

Electron-on-solid-neon (eNe) qubits have shown great promise as ideal qubits owing to their long coherence time, fast operation speed, and compact footprint. Previously, we have achieved strong coupling between an eNe charge qubit and microwave photons in a niobium (Nb) superconducting resonator, about 0.1-millisecond long relaxation and coherence times, and high-fidelity single-qubit gates and readout. Realization of two-qubit gates is the next step. Although we have demonstrated simultaneous coupling of two eNe qubits to a common Nb resonator, the coupling strength was not enough for two-qubit entangling gates. Here we report enhanced charge-photon coupling strength into 10-30 MHz range, with a high-impedance superconducting resonator made of 30 nm thick high-kinetic-inductance titanium nitride (TiN) films on intrinsic silicon substrates. This progress paves the way towards strong-dispersive coupling between two eNe qubits and realization of two-qubit gates. We have also observed avoided crossings on the 100 MHz scale between two qubits with near-field dipole-dipole interaction. All these results indicate the potential scalability of eNe qubits.