A quantum state router based on parametrically driven photon exchange

Precisely controlled couplings between qubits are a vital part of all quantum information processing. For superconducting qubits, most efforts seek to implement a “surface code” architecture, which only couples nearest-neighbor qubits. However, longer range couplings are very desirable as they reduce the overhead of interactions between distant qubits. We present a design that can realize long range couplings between qubits through a modular quantum router. The design contains a 3D superconducting waveguide ‘trunk’ of microwave modes and a Superconducting Nonlinear Asymmetric Inductive eLement (SNAIL) to generate parametric photon exchange couplings between each pair of modes. We couple individual modules via a communication cavity deliberately detuned from a corresponding waveguide mode, with resulting (weaker) parametric couplings directly from module to module. Quantum information is exchanged between modules by driving the SNAIL at the difference of the communication modes’ frequencies. We will present a theory treatment of our router’s performance, as well as experimental results from our realization in an aluminum waveguide prototype.