Long-Range Big Quantum-Data Transmission

We introduce an alternative type of quantum repeater for long-range quantum communication with improved scaling with the distance. We show that by employing hashing, a deterministic entanglement distillation protocol with one-way communication, one obtains a scalable scheme that allows one to reach arbitrary distances, with constant overhead in resources per repeater station, and ultrahigh rates. In practical terms, we show that, also with moderate resources of a few hundred qubits at each repeater station, one can reach intercontinental distances. At the same time, a measurement-based implementation allows one to tolerate high loss but also operational and memory errors of the order of several percent per qubit. This opens the way for long-distance communication of big quantum data.

Figure 1

Illustration of a quantum repeater based on hashing. The channel is divided into $N$ elementary segments, where short-distance entangled pairs are generated over all segments, i.e., between all repeater stations, in parallel. Entanglement distillation via hashing and entanglement swapping are performed in a measurement-based way, by coupling the elementary pairs via Bell measurements to the locally stored resource state. In contrast to quantum repeaters based on recurrence protocols, no nesting is required. Direct encoded transmission would consist in sending encoded information sequentially through the channel. Please note that this is only an illustration; the real resource states contain at least the order of 100 qubits.

Figure 2

Plot of the global, private fidelity and yield as a function of the number of initial pairs for $\delta =n^{-1/5}$ (a),(b) and $\delta =n^{-1/3}$ (c),(d). $F$ denotes the fidelity of the initial Bell pairs, and the number of repeater links is $N=100$. We assume a local depolarizing noise of 1% per qubit. The fact that the blue curve in (a) seems to starts “out of the blue” at around $n\approx 600$ is a consequence of the vanishing yield below this number [see (b)]. In the choice of $\delta$, there is trade-off between a higher fidelity (larger $\delta$) and a higher yield (smaller $\delta$). Additional data for more links can be found in Ref. [37].