Abstract: Methods, apparatus, and computer program products for quantum communications and quantum information processing are provided. An example method includes determining a received state of a qubit received via a quantum communication link where the received state includes one or more properties of the received qubit. The method further accesses a transmitted state of the qubit where the transmitted state includes one or more properties of the qubit as transmitted. The method continues by comparing the one or more properties of the qubit in the received state with the one or more properties of the qubit in the transmitted state. Finally, the method detects a condition of the quantum communication link based on the comparison between the received state and the transmitted state. In doing so, the embodiments operate to characterize the noise level, security, etc. of a quantum communication interconnect, link, or channel.

Abstract: Various embodiments of the present disclosure are directed to accessing a quantum communication channel undetected and/or characterizing this communication channel based upon attempted access. An example method includes accessing a quantum communication channel transmitting one or more qubits. The method includes the introduction of a noise signal to the quantum communication channel and then applying in its absence one or more weak or variable-strength measurements to the quantum communication channel. A strength of at least one measurement of the one or more measurements is based at least in part upon the current noise signal. The method further includes obtaining information associated with the one or more qubits based on the one or more measurements.

Abstract: Embodiments are disclosed for providing quantum-classical hybrid security. An example system includes a hybrid quantum-classical transmitter device. The hybrid quantum-classical transmitter device includes a classical transmitter and a quantum transmitter. The classical transmitter is configured to generate data based on a cryptography technique. The classical transmitter is also configured to generate a classical bitstream representation of the data, where the classical bitstream is configured for transmission via an optical communication channel. The quantum transmitter is configured to embed one or more qubits into the classical bitstream to generate a hybrid quantum-classical bitstream for transmission via the optical communication channel.