A communications system comprises first circuitry for receiving and processing a plurality of data streams to associate with each of the plurality of data streams an orthogonal function to cause each of the plurality of data streams to be mutually orthogonal to each other on a link to enable transmission of each of the plurality of data streams on the link at a same time. First quantum key processing circuit generates a secret key for transmissions to second circuitry over the link using a quantum key generation process based on E91 protocol. The first quantum key processing circuit further encoding the plurality of data streams for transmission on the link using the generated secret key based on the E91 protocol. Third circuitry transmits the encoded plurality of data streams on the link.