We theoretically propose a new way to realize qubits: a hybrid qubit system consisting of the quantized vertical motion (Rydberg states) and the spin states of electrons on the surface of liquid helium.

Introducing a local magnetic field gradient hybridizes the Rydberg and spin degrees of freedom, which allows us to benefit from both the long coherence time of the spin state and the long-range Coulomb interaction between electrons that couples the Rydberg state. We present concrete schemes to realize single- and two-qubit gates and quantum-non-demolition read-out. In our framework, the hybridization of the Rydberg state and the spin state is large enough to perform fast qubit gates and small enough not to degrade the coherence time of the spin state significantly, which leads to the realization of high-fidelity qubit gates.

consisting of the quantized vertical motion (Rydberg states) and the spin

states of electrons on the surface of liquid helium. Introducing a local

magnetic field gradient hybridizes the Rydberg and spin degrees of freedom,

w…