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Filip Rozpedek, University of Chicago/University of Massachusetts Amherst

Quantum repeaters based on concatenated bosonic and discrete-variable quantum codes

Abstract:

Long distance quantum communication will require the use of quantum repeaters to overcome the exponential attenuation of signal with distance. One class of such repeaters utilizes quantum error correction to overcome losses in the communication channel. We propose two architectures of quantum-error-correction-based quantum repeaters that combine techniques used in discrete- and continuous-variable quantum information. Our first scheme is a one-way repeater architecture, while the second scheme is a two-way all-photonic repeater scheme. In these schemes, we propose to encode the qubits in a concatenated code consisting of two levels. On the first level we use a continuous-variable GKP code encoding the qubit in a single bosonic mode. On the second level we use a small discrete-variable code. The crucial feature of our schemes is the use of the GKP analog information which serves multiple purposes. Firstly, it enhances the error-correcting capabilities of the second-level code. Secondly, it allows for designing better entanglement swapping strategies where multiplexed links can be connected according to their expected quality. We find that our architectures allow for high-rate end-to-end entanglement generation and are resilient to imperfections arising from finite squeezing in the GKP state preparation.

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