  Modular quantum computing architectures require fast and efficient
distribution of quantum information through propagating signals. Here we report
rapid, on-demand quantum state transfer between two remote superconducting
cavity quantum memories through traveling microwave photons. We demonstrate a
quantum communication channel by deterministic transfer of quantum bits with
76% fidelity. Heralding on errors induced by experimental imperfection can
improve this to 87% with a success probability of 0.87. By partial transfer of
a microwave photon, we generate remote entanglement at a rate that exceeds
photon loss in either memory by more than a factor of three. We further show
the transfer of quantum error correction code words that will allow
deterministic mitigation of photon loss. These results pave the way for scaling
superconducting quantum devices through modular quantum networks.
