Abstract: A scalable platform for generating time-frequency-multiplexed cluster states and utilizing them for large-scale quantum computing. Kerr microcombs and continuous-variable (CV) quantum information are used to formulate a one-way quantum computing architecture that can accommodate hundreds of simultaneously addressable entangled optical modes multiplexed in the frequency domain and an unlimited number of sequentially addressable entangled optical modes in time domain. One-dimensional, two-dimensional, and three-dimensional CV cluster states can be deterministically produced using robust integrated photonic circuit technology is leveraged that is readily available and experimentally viable.

Abstract: A system for entanglement-enhanced machine learning with quantum data acquisition includes a first variational circuit that generates a plurality of entangled probe light fields that interacts with a sample and is then processed by a second variational quantum circuit to produce at least one detection light field, a detector is used to measure a property of the at least one detection light field, and the first and second variational quantum circuits are optimized though machine learning. A method for entanglement-enhanced machine learning with quantum data acquisition includes optimizing a setting of a first and second variational quantum circuits, which includes probing a training-set with a plurality of entangled probe light fields generated by the first variational quantum circuit, and measuring a phase property of at least one detection light fields generated by the second variational quantum circuit from the plurality of entangled probe light fields after interaction with the training-set.

Abstract: A reconfigurable sensor network uses continuous-variable (CV) multipartite entangled quantum states for distributed RF sensing with uncertainties below the standard quantum limit. A CV multipartite entangled state is generated with a quantum circuit that splits a squeezed vacuum state into spatially separated optical modes that are entangled. Each optical mode is transmitted to a RF-photonic sensor that imposes, on the corresponding optical mode, a quadrature displacement based on the local properties of an RF signal. A homodyne detector then measures the quadrature displacement. A post-processor combines the measurements to estimate a global property of the RF signal, such as an angle-of-arrival. To enable distributed sensing over large distances, the RF-photonic sensors may be spatially separated by several kilometers, or more. Alternatively, the RF-photonic sensors may be integrated into a single photonic system, such as a photonic integrated circuit.

Abstract: A reconfigurable sensor network uses continuous-variable (CV) multipartite entangled quantum states for distributed RF sensing with uncertainties below the standard quantum limit. A CV multipartite entangled state is generated with a quantum circuit that splits a squeezed vacuum state into spatially separated optical modes that are entangled. Each optical mode is transmitted to a RF-photonic sensor that imposes, on the corresponding optical mode, a quadrature displacement based on the local properties of an RF signal. A homodyne detector then measures the quadrature displacement. A post-processor combines the measurements to estimate a global property of the RF signal, such as an angle-of-arrival. To enable distributed sensing over large distances, the RF-photonic sensors may be spatially separated by several kilometers, or more. Alternatively, the RF-photonic sensors may be integrated into a single photonic system, such as a photonic integrated circuit.

Abstract: A photonic integrated circuit (PIC) includes a first microresonator that generates a two-mode squeezed vacuum using spontaneous four-wave mixing. Specifically, the first microresonator uses a nonlinear optical medium to convert two pump photons into a pair of entangled signal and idler photons. Due to imperfect conversion efficiency, some of the pump light may co-propagate with the signal light and idler light. To remove this “unconverted” pump light, the PIC includes a second microresonator that is tuned to resonate with only the pump light. The second microresonator is located after the first microresonator and couples the unconverted pump light into a waveguide that guide the light off the PIC. Thus, the second microresonator acts as a notch filter. Integrating this pump filter onto the PIC adds negligibly to the path length of the squeezed light, and therefore saves the propagation losses incurred when using a much larger off-chip filter.

Abstract: A quantum receiver for decoding an optical signal includes a beamsplitter for interfering the optical signal with a local-oscillator field to generate a displaced field, and a single-photon detector for detecting the displaced field. The quantum receiver also includes a signal-processing circuit for determining, based on an electrical output of the single-photon detector, a measurement outcome. The signal-processing circuit also determines, based on the measurement outcome and a feed-forward machine-learning model, a next displacement. The quantum receiver also includes at least one modulator for modulating, based on the next displacement, one or both of the optical signal and the local-oscillator field. Like a Dolinar receiver, the quantum receiver implements adaptive measurements to reduce the error probability of the decoded symbol. The use of machine-learning reduces the latency of the signal-processing circuit, thereby increasing the number of measurements that may be performed for each received symbol.

Abstract: A quantum receiver for decoding an optical signal includes a beamsplitter for interfering the optical signal with a local-oscillator field to generate a displaced field, and a single-photon detector for detecting the displaced field. The quantum receiver also includes a signal-processing circuit for determining, based on an electrical output of the single-photon detector, a measurement outcome. The signal-processing circuit also determines, based on the measurement outcome and a feed-forward machine-learning model, a next displacement. The quantum receiver also includes at least one modulator for modulating, based on the next displacement, one or both of the optical signal and the local-oscillator field. Like a Dolinar receiver, the quantum receiver implements adaptive measurements to reduce the error probability of the decoded symbol. The use of machine-learning reduces the latency of the signal-processing circuit, thereby increasing the number of measurements that may be performed for each received symbol.

Abstract: An entangled, spatially distributed, quantum sensor network enhanced by quantum repeaters includes a probe-state generator for generating M entangled light fields, where M is an integer greater than one. The quantum sensor network also includes M spatially distributed sensor modules that communicate with the probe-state generator to receive the M entangled light fields, respectively, and conduct a measurement therewith. The quantum sensor network also includes one or more quantum repeaters, each of which is (a) located in a propagation channel of a respective one of the entangled light fields to its corresponding sensor module from the probe-state generator, and (b) includes a plurality of quantum scissors to amplify the entangled light field to at least partly compensate for loss in the propagation channel.

Abstract: A system for entanglement-enhanced machine learning with quantum data acquisition includes a first variational circuit that generates a plurality of entangled probe light fields that interacts with a sample and is then processed by a second variational quantum circuit to produce at least one detection light field, a detector is used to measure a property of the at least one detection light field, and the first and second variational quantum circuits are optimized though machine learning. A method for entanglement-enhanced machine learning with quantum data acquisition includes optimizing a setting of a first and second variational quantum circuits, which includes probing a training-set with a plurality of entangled probe light fields generated by the first variational quantum circuit, and measuring a phase property of at least one detection light fields generated by the second variational quantum circuit from the plurality of entangled probe light fields after interaction with the training-set.

Abstract: A method for distributing a quantum digital key is described. The method comprises the use of an optical broadband source to generate an optical broadband signal. The optical broadband signal may be transmitted from a first party to a second party through an optical communication channel. The optical broadband signal may be transmitted with a low brightness, such as less than one photon/(sec-Hz), so as to be immune from passive attacks. Furthermore, a method for detecting the presence of active attackers is described. The method may comprise a coincidence measurement configured to measure the level of entanglement between an optical detection signal and an optical idler signal.

Abstract: A method for distributing a quantum digital key is described. The method comprises the use of an optical broadband source to generate an optical broadband signal. The optical broadband signal may be transmitted from a first party to a second party through an optical communication channel. The optical broadband signal may be transmitted with a low brightness, such as less than one photon/(sec-Hz), so as to be immune from passive attacks. Furthermore, a method for detecting the presence of active attackers is described. The method may comprise a coincidence measurement configured to measure the level of entanglement between an optical detection signal and an optical idler signal.