Gate-based microwave quantum repeater via grid-state encoding
Phys. Rev. Applied 26, 024003 – Published 5 August, 2026
DOI: https://doi.org/10.1103/pg3m-jx2k
Abstract
In autonomous quantum error correction, the lifetime of a logical bosonic qubit can be extended beyond its physical constituents without feedback measurements. Leveraging autonomous error correction, we propose a gate-based microwave quantum repeater (GBMQR) with encoded bosonic grid states. Each repeater station comprises a transmon and two bosonic resonators: one resonator serves as a stationary quantum memory utilizing autonomous error correction and the other serves as an information bus for entanglement generation. Entanglement is generated sequentially through the successful absorption of a microwave photon wave packet. This method enables deterministic entanglement generation, in contrast to a probabilistic mixing of two heralding signals on a balanced beam splitter. Furthermore, our GBMQR employs an all-bosonic entanglement swapping Bell-state measurement. This is implemented via a bosonic controlled- gate and two separate -basis projective homodyne measurements on the stationary stored code words. Our approach circumvents mode-mismatch losses associated with routing and interfering heralding modes on a beam splitter and confines losses to those arising from stationary storage. We evaluate the performance of the proposed quantum repeater by calculating its secret key rate under realistic laboratory environments. Moreover, we explicitly demonstrate that at the stationary damping rate of , GBMQR can achieve entanglement generation and swapping success probabilities of approximately 0.75 and 0.58, respectively, surpassing the hallmark success probability of set by ideal linear beam-splitter-based Bell-state measurements. The proposed device can be implemented using currently available superconducting microwave technology and is suited for secure chip-to-chip communication and distributed quantum computing.
