Abstract: A quantum communications system may include a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter, a pulse divider downstream from the pulse transmitter, and at least one first waveplate upstream from the pulse divider and configured to alter a polarization state of pulses travelling therethrough. The receiver node may include at least one second waveplate being a conjugate of the at least one first waveplate, a pulse recombiner upstream from the at least one second waveplate, and a pulse receiver downstream from the at least one second waveplate.

Abstract: A quantum communications system includes a communications system that operates with a quantum key distribution (QKD) system, which includes a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to transmit to the receiver node a bit stream of optical pulses, and switch between first and second QKD protocols based upon at least one channel condition.

Abstract: A sensor receiver may include a Rydberg cell configured to be exposed to a radio frequency (RF) signal, and a probe source configured to generate a plurality of spaced apart pulsed probe beams within the Rydberg cell. The pulsed probe beams may be offset in time from one another. A plurality of excitation sources may be coupled to the Rydberg cell. A detector may be positioned downstream from the Rydberg cell.

Abstract: A sensor receiver may include a Rydberg cell configured to be exposed to a radio frequency (RF) signal having an RF data rate, and a probe source configured to generate a plurality of spaced apart pulsed probe beams within the Rydberg cell. Each pulse may have a temporal pulse width so that the RF data rate is greater than the reciprocal of the temporal pulse width. At least one excitation source may be coupled to the Rydberg cell. A detector may be positioned downstream from the Rydberg cell. The sensor receiver may be used in a RADAR system.

Abstract: A quantum communications system may include a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter, a pulse divider downstream from the pulse transmitter, and at least one first waveplate upstream from the pulse divider and configured to alter a polarization state of pulses travelling therethrough. The receiver node may include at least one second waveplate being a conjugate of the at least one first waveplate, a pulse recombiner upstream from the at least one second waveplate, and a pulse receiver downstream from the at least one second waveplate.

Abstract: A quantum communications system may include a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter and pulse divider downstream therefrom. The receiver node may include a pulse recombiner and a pulse receiver downstream therefrom.

Abstract: A sensor receiver includes a Rydberg cell configured to be exposed to a radio frequency (RF) signal, and a probe source configured to generate a plurality of spaced apart pulsed probe beams within the Rydberg cell. The pulsed probe beams are offset in time from one another. A detector is positioned downstream from the Rydberg cell.

Abstract: A sensor receiver may include a Rydberg cell configured to be exposed to a radio frequency (RF) signal, and a probe source configured to generate a plurality of spaced apart pulsed probe beams within the Rydberg cell. The pulsed probe beams may be offset in time from one another. A plurality of excitation sources may be coupled to the Rydberg cell. A detector may be positioned downstream from the Rydberg cell.

Abstract: A sensor receiver includes a Rydberg cell configured to be exposed to a radio frequency (RF) signal, and a probe source configured to generate a plurality of spaced apart pulsed probe beams within the Rydberg cell. The pulsed probe beams are offset in time from one another. A detector is positioned downstream from the Rydberg cell.

Abstract: Systems and methods for operating a quantum network system. The methods comprise, by a network node: generating optical clock pulses and photons using the optical clock pulses; generating a combined signal by combining the optical clock pulses with at least some of the photons such that a consistent temporal offset exits between the optical clock pulses and the first photons and/or a wave function of each photon at least partially overlaps an envelope of a respective one of the optical clock pulses; and transmitting the combined signal over a first quantum channel in which the optical clock pulses co-propagate with the photons.

Abstract: An underwater communications system may include a first device and a second device being movable relative to one another. The first device may include a first laser transmitter configured to generate a first laser beam having a selectable spatiotemporal beam shape from among a plurality thereof, and a first controller coupled to the first laser transmitter and configured to select a spatiotemporal beam shape for the first laser beam from among the spatiotemporal beam shapes. The second device may include a second laser receiver configured to receive the first laser beam, and a second controller coupled to the second laser receiver.

Abstract: A quantum communications system may include transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to co-propagate a first pulse for a quantum state and a second pulse to stabilize the quantum state through the quantum communications channel.

Abstract: A communications system may include a transmitter node, a receiver node, and an optical communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter and a pulse divider downstream therefrom. The receiver node may include a pulse recombiner and a pulse receiver downstream therefrom.

Abstract: A quantum communications system includes a communications system that operates with a quantum key distribution (QKD) system, which includes a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to transmit to the receiver node a bit stream of optical pulses, and switch between first and second QKD protocols based upon at least one channel condition.

Abstract: An underwater communications system may include a first device and a second device being movable relative to one another. The first device may include a first laser transmitter configured to generate a first laser beam having a selectable spatiotemporal beam shape from among a plurality thereof, and a first controller coupled to the first laser transmitter and configured to select a spatiotemporal beam shape for the first laser beam from among the spatiotemporal beam shapes. The second device may include a second laser receiver configured to receive the first laser beam, and a second controller coupled to the second laser receiver.

Abstract: A quantum communications system may include a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter and a pulse divider downstream therefrom. The pulse divider may be configured to divide each pulse having a plurality of X photons into a plurality of Y time bins with Y>X. The receiver node may include a pulse recombiner and a pulse receiver downstream from the pulse recombiner.

Abstract: A communications system may include a transmitter node, a receiver node, and an optical communications channel coupling the transmitter node and receiver node. The transmitter node may include a pulse transmitter and a pulse divider downstream therefrom. The receiver node may include a pulse recombiner and a pulse receiver downstream therefrom.

Abstract: A quantum communications system may include transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to co-propagate a first pulse for a quantum state and a second pulse to stabilize the quantum state through the quantum communications channel.

Abstract: A quantum communications system includes a communications system that operates with a quantum key distribution (QKD) system, which includes a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The transmitter node may be configured to transmit to the receiver node a bit stream of optical pulses, and switch between first and second QKD protocols based upon at least one channel condition.

Abstract: A quantum communications system may include a transmitter node, a receiver node, and a quantum communications channel coupling the transmitter node and receiver node. The receiver node may be configured to arrange a received bit stream of optical pulses from the transmitter node into time bins, convert the optical pulses in the time bins into corresponding optical pulses in frequency bins, and detect respective optical pulse values from each of the frequency bins.