A device for routing arbitrary microwave quantum states in waveguide quantum electrodynamics

Routing traveling photons in a controlled directional manner is essential for operating a quantum network. Communicating information between arbitrary quantum nodes using itinerant photons requires controllable directionality. In addition, such a network will require high fidelity signal routing and loss resilience. However, implementing such a network in the microwave domain is currently limited by losses due to commercially available directional devices such as circulators and isolators [1-3]. Recent efforts having been made [4] to address this issue and have demonstrated controlled directional emissions of flying qubit states in the 0/1 Fock state basis. Here we present a theoretical proposal that extends this functionality to arbitrary quantum states, such as error-correctable bosonic states. We have designed a parametrically controllable lossless directional device that utilizes the interference between a memory mode and two SNAIL (Superconducting Nonlinear Asymmetric Inductive eLement) modes coupled to a common transmission line. By parametrically tuning the interaction between the memory mode and the SNAILs via microwave pumps, the device can emit and absorb arbitrary photonic wave packets with in-situ tunable directionality and negligible loss. We will present both analytical and numerical analysis for our design, along with preliminary data on parametrically controlling the couplings between the SNAIL and memory modes. Our result demonstrates a powerful design for routing arbitrary quantum states with in-situ control, which will be an enabling component for remote entanglement distribution and state transfer in error-corrected modular quantum networks.



[1] Campagne-Ibarcq, P., et al. Physical review letters 120.20 (2018): 200501.

[2] Axline, Christopher J., et al. Nature Physics 14.7 (2018): 705-710.

[3] Kurpiers, Philipp, et al. Nature 558.7709 (2018): 264-267.

[4] Kannan, Bharath, et al. arXiv preprint arXiv:2203.01430 (2022).