Downloading many-qubit entanglement from continuous-variable cluster states

Synopsis

Many-body entanglement is the essential resource for many quantum technologies, but its scalable generation has been challenging on qubit platforms. On the other hand, the generation of continuous-variable (CV) entanglement can be extremely efficient, over a million entangled bosonic modes have already been realized. In our work, we introduce a hybrid approach to generate many-qubit entanglement by downloading it from the efficiently generated CV cluster states. Our protocol is based on teleporting to qubits the correlation encoded in the displaced Gottesman-Kitaev-Preskill basis. To characterize the practical performance of our scheme, we develop an equivalent circuit to map dominant CV errors to single qubit preparation errors. For finite squeezing error, we show that only 5.4 dB squeezing is sufficient for robust qubit memory, and 11.9 dB for fault-tolerant quantum computation. We also show that although channel loss and detection inefficiency introduce correlated dephasing, the error can be localized by compensating the correlation through linearly transforming the initial CV cluster state. Our protocol can be implemented with the operations that can be commonly found in many bosonic platforms and does not require strong hybrid coupling.