Schrodinger's catapult I: coherent launch of multi-photon cavity states

Quantum networks are a powerful paradigm for managing complexity in quantum information processing. Here we present a circuit QED tool to control the exchange of quantum information in such a network, dubbed "Schrodinger's catapult". It enables rapid conversion between complex, multi-photon states prepared in a cavity memory and a propagating output mode. Enabled by four-wave mixing in a single Josephson junction, this conversion rate is tunable up to three orders of magnitude faster than the intrinsic memory decay rate. In addition to such a large on/off ratio, we show that the mapping of cavity states to traveling states is faithful and state-independent. Amplitude and phase control of the conversion process anticipates the capture of propagating states using a reciprocal module.