  Quantum repeaters with multiple quantum memories provide high throughput, low
latency, and high fidelity quantum state (qubit) transfer over long distances.
However, conventional quantum repeater protocols require full connections among
the multiple quantum memories in a repeater node, which is technically
challenging. Here, we propose a quantum repeater protocol based on backward
propagating photon emission and absorption, where the quantum memories are
multiplexed in the time-domain to speed up a single transmission channel
without requiring full connectivity, drastically facilitating physical
implementation. Although the protocol is described with nitrogen-vacancy (NV)
centers in diamond, it is applicable to various physical systems and opens up
the possibility of high-speed high-fidelity quantum networks for distributed
quantum computation and quantum Internet.
