Quantum information processing using quasiclassical electromagnetic interactions between qubits and electrical resonators

Electrical resonators are widely used in quantum information processing with any qubits that are manipulated via electromagnetic interactions. In nearly all examples to date they are engineered to interact with qubits via real or virtual exchange of (typically microwave) photons, and the resonator must therefore have both a high quality factor and strong quantum fluctuations, corresponding to the strong-coupling limit of cavity QED. Although great strides in the control of quantum information have been made using this so-called „circuit QED“ architecture, it also comes with some characteristic limitations. In this paper, we discuss a new paradigm for coupling qubits electromagnetically via resonators, in which the qubits do not exchange photons with the resonator, but instead where the qubits exert quasi-classical, effective „forces“ on it. We show how this type of interaction is similar to that induced between the internal state of a trapped atomic ion and its center-of-mass motion by the photon recoil momentum, and that the resulting multiqubit entangling operations are insensitive textit{both to the state of the resonator and to its quality factor}. The method we describe is potentially applicable to a variety of qubit modalities, including superconducting and semiconducting solid-state qubits, trapped molecular ions, and possibly even electron spins in solids.