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.

A quantum key distribution device is provided with an encoding unit which encodes an optical pulse train; an intensity modulating unit which subjects the encoded optical pulse train to N (where N is an integer at least equal to 3) types of intensity modulation having mutually different intensities, with different timings; and a first key distillation processing unit which generates an encryption key on the basis of a data sequence obtained by removing data obtained from an optical pulse having a specific modulation pattern from a data sequence used by the encoding unit and the intensity modulating unit.

A quantum key distribution device is provided with an encoding unit which encodes an optical pulse train; an intensity modulating unit which subjects the encoded optical pulse train to N (where N is an integer at least equal to 3) types of intensity modulation having mutually different intensities, with different timings; and a first key distillation processing unit which generates an encryption key on the basis of a data sequence obtained by removing data obtained from an optical pulse having a specific modulation pattern from a data sequence used by the encoding unit and the intensity modulating unit.

A circuit configured to transmit frequency multiplexed signals from a superconducting domain to a higher temperature domain. The circuit comprising a multiplexed signal output and a plurality of superconducting oscillator circuits each configured to output a different carrier frequency, each superconducting oscillator circuit comprising an oscillator output connected to the multiplexed signal output. Each superconducting oscillator circuit comprising a converter stage configured to convert an input of a superconducting logic signal to a Single Flux Quantum (SFQ) bit value, a splitter stage electrically connected to an output of the converter stage, the splitter stage configured to change between a first current state and a second current state based at least in part on the SFQ bit value, and an oscillator stage magnetically coupled to an output of the splitter stage and electrically coupled to the oscillator output. The oscillator stage comprising a direct current superconducting quantum interference device (DC SQUID).

A circuit configured to transmit frequency multiplexed signals from a superconducting domain to a higher temperature domain. The circuit comprising a multiplexed signal output and a plurality of superconducting oscillator circuits each configured to output a different carrier frequency, each superconducting oscillator circuit comprising an oscillator output connected to the multiplexed signal output. Each superconducting oscillator circuit comprising a converter stage configured to convert an input of a superconducting logic signal to a Single Flux Quantum (SFQ) bit value, a splitter stage electrically connected to an output of the converter stage, the splitter stage configured to change between a first current state and a second current state based at least in part on the SFQ bit value, and an oscillator stage magnetically coupled to an output of the splitter stage and electrically coupled to the oscillator output. The oscillator stage comprising a direct current superconducting quantum interference device (DC SQUID).

A quantum communication system that includes a multiphoton entanglement generator, a plurality of photon detector units, and a plurality of optical fiber links. The plurality of photon detector units include a first photon detector unit and a second photon detector unit. The multiphoton entanglement generator is structurally configured to output more than two entangled photons. The plurality of optical fiber links comprise a first optical fiber link optically coupled to the multiphoton entanglement generator and disposed between the multiphoton entanglement generator and the first photon detector unit. The plurality of optical fiber links comprise a second optical fiber link optically coupled to the multiphoton entanglement generator and disposed between the multiphoton entanglement generator and the second photon detector unit. Further, at least one of the plurality of optical fiber links has a core, a cladding, and a scattering region having a plurality of scattering structures.

A quantum communication system that includes a multiphoton entanglement generator, a plurality of photon detector units, and a plurality of optical fiber links. The plurality of photon detector units include a first photon detector unit and a second photon detector unit. The multiphoton entanglement generator is structurally configured to output more than two entangled photons. The plurality of optical fiber links comprise a first optical fiber link optically coupled to the multiphoton entanglement generator and disposed between the multiphoton entanglement generator and the first photon detector unit. The plurality of optical fiber links comprise a second optical fiber link optically coupled to the multiphoton entanglement generator and disposed between the multiphoton entanglement generator and the second photon detector unit. Further, at least one of the plurality of optical fiber links has a core, a cladding, and a scattering region having a plurality of scattering structures.

A node may receive, from a quantum key-distribution (QKD) device, a first message that includes an identifier associated with a key. The node may send, to another node, a second message that includes the identifier and a request to perform at least one task. A node may receive, from the other node, a third message that includes information associated with performance of the at least one task by the other node and information indicating a time of performance. The node may receive, from the QKD device, a fourth message that includes the key and information indicating a time window associated with the quantum key; wherein the fourth message is received after expiration of the time window. The node may process, based on the fourth message, the third message to determine whether the third message is valid and thereby cause one or more actions to be performed.

Aspects of the present disclosure describe techniques for controlling coherent crosstalk errors that occur in multi-channel acousto-optic modulators (AOMs) by applying cancellation tones to reduce or eliminate the crosstalk errors. For example, a method and systems are described that include applying a first radio frequency (RF) tone to generate a first acoustic wave in a first channel of the multi-channel AOM, wherein a portion of the first acoustic wave interacts with a second channel to cause a crosstalk effect, and applying a second RF tone to generate a second acoustic wave in the second channel, wherein the second acoustic wave reduces or eliminates the crosstalk effect caused by the portion of the first acoustic wave.

An adiabatic coupling phase modulation module has an optical substrate, an asymmetric adiabatic coupling polarization beam splitter and two electro-optical phase modulators. The asymmetric adiabatic coupling polarization beam splitter performs band spatial filtering on a quantum light source signal to output a light source signal of a specific wavelength band, and performs polarization spatial filtering on the light source signal of specific wavelength band to output a first orthogonal polarization direction light source signal of the specific wavelength band and a second orthogonal polarization direction light source signal of the specific wavelength band. The two electro-optical phase modulators respectively perform phase coding processes on the first orthogonal polarization direction light source signal and the second orthogonal polarization direction light source signal.