All-photonic two-way quantum repeaters with multiplexing based on concatenated bosonic and discrete-variable quantum codes

Long distance quantum communication will require use of quantum repeaters which allow for overcoming exponential signal attenuation with distance. One class of such repeaters utilizes quantum error correction to overcome losses in the communication channel. Here we propose a novel strategy of using the Gottesman-Kitaev-Preskill (GKP) code in a two-way repeater architecture with multiplexing. The crucial feature of the GKP code that we make use of, is the fact that GKP qubits easily admit deterministic two-qubit gates, hence allowing for multiplexing without the need for generating large cluster states as proposed in previous all-photonic architectures based on discrete variable codes. Furthermore, thanks to the availability of the analog information generated during the measurement of the GKP qubits, we can design better entanglement swapping procedures. To boost the loss-resilience of our encoded qubits, we consider a concatenation of the GKP code with the discrete variable [[7,1,3]] code which has already proven effective in the context of quantum repeater schemes. We find that our architecture allows for high-rate near-deterministic end-to-end entanglement generation and is resilient to imperfections arising from finite squeezing in the GKP state preparation.