  We answer an open question about Quantum Key Recycling (QKR): Is it possible
to put the message entirely in the qubits without increasing the number of
qubits? We show that this is indeed possible. We introduce a
prepare-and-measure QKR protocol where the communication from Alice to Bob
consists entirely of qubits. As usual, Bob responds with an authenticated
one-bit accept/reject classical message. Compared to Quantum Key Distribution
(QKD), QKR has reduced round complexity. Compared to previous qubit-wise QKR
protocols, our scheme has far less classical communication. We provide a
security proof in the universal composability framework and find that the
communication rate is asymptotically the same as for QKD with one-way
postprocessing.
