At&t Intellectual Property I, L.p.

US Government As Represented by the Secretary of the Army

Michael Brodsky

Cristian Antonelli

Jungmi Oh

Daniel E Jones

Brian T Kirby

Robert James Drost

Xiang Zhou

Martin Birk

Sheryl Leigh Woodward

Mark David Feuer

Lynn Nelson

Vladimir S Malinovsky

Terrence Joseph Moore

Gabriele Riccardi

Siddhartha Santra

Dashiell L Vitullo

Michael Sumetsky

Sajid Zaki

Various embodiments are directed to systems, apparatus and methods for characterizing evanescent coupling parameters of a waveguide coupled to a resonator through variation of their relative positions. Various embodiments extend a local coupling approach with novel fitting capabilities that robustly determine the bare resonator modes and coupling parameters with quantified residual error and coupling parameter uncertainty estimates.

Control of resonant optical evanescent coupling between waveguides and resonators

Systems, apparatus and methods for defining an impairment profile along a polarization quantum channel such as in terms of modal loss and decoherence. The disclosed impairment profile or characterization methods may be used as part of a tool such as to inform a network operator of a weakest span of the communication channel, thus facilitating optimal signal routing decisions.

Method and apparatus for mapping out sources of decoherence in quantum channels

A quantum key distribution system is deployed in an optical fiber network transporting classical data traffic. A source of entangled photon pairs is used to generate quantum keys. Classical data traffic is typically transported over channels in the C-band. If a pair of channels for transport of quantum data is available within the C-band, then the source of entangled photon pairs is tuned to emit in a pair of channels in the C-band. If a pair of channels for transport of quantum data is not available within the C-band, then the source of entangled photon pairs is tuned to emit in a pair of channels in a combined S-band and L-band. When a periodically-poled lithium niobate waveguide pumped with a laser is used for the source of entangled photon pairs, the output spectral properties are tuned by varying the temperature of the waveguide.

Bandwidth provisioning for an entangled photon system

A novel methodology for characterizing and calibrating an entangled photon distribution system is disclosed. The entangled photon distribution system includes at least a source of entangled photon pairs, two photon detectors which detect photons among two channels and a controller. The methodology includes: for at least two different operational setting levels of the source of entangled photon pairs, measuring count rates for photons detected by the two photon detectors, individually and coincidently; fitting the measured individual and coincidence count rate data for the at least two different operational setting levels with theoretical models of detection probability; and determining operational parameters of the system from the fitting. The determined operational parameters of the system include the rate of generated entangled photon pairs by the source, the rates of Raman-scattered photons generated in the first and second channels, respectively, and the efficiency of the two photon detectors, respectively.

Methodology for in situ characterizing and calibrating an entangled photon distribution system

Methods and apparatuses are provided that compensate for the polarization dependent loss (PDL) of fiber-optic quantum channels. Compensation is accomplished by inserting a compensating PDL into another quantum channel carrying entangled photons that are entangled with photons in the first channel having losses that are to be compensated for. By selecting the optimum magnitude and orientation for the compensating PDL, compensation for the PDL in the first channel is maximized.

Compensating for entanglement loss in communication lines

Methods and systems for measuring interferometric visibility of telescopic signals using resources having imperfect quantum entanglement are disclosed. The novel methodology employed by embodiments of the present invention takes into account the difficulty in creating entanglement between distance telescopes, and describes how to incorporate problems associated with distributing quantum entanglement into the measurement procedure. This allows the distance that two telescopes in an optical array are spaced apart to be increased while still interacting.

Method and system for measuring interferometric visibility of telescopic signals having imperfect quantum entanglement

Operational parameters of a single-photon detector are determined with a continuous wave laser source. At a fixed trigger, a dark count probability and a series of count probabilities at different optical powers are determined. A particular optical power is selected by using a wide-range variable attenuator to attenuate the optical power of the continuous wave laser. The dark count probability and the count probabilities are determined for different trigger rates. The operational parameters include efficiency, afterpulsing constant, and detrap time. The operational parameters are computed by fitting the computed dark count probabilities and count probabilities to a user-defined relationship.

Characterization of single-photon detectors using a continuous wave laser source

Quantum networking systems and methods for routing entangled photons pairs are described herein. One quantum networking system includes entangled photon sources which generate entangled photons; optical output ports; a reconfigurable switching network connecting to the entangled photon sources and the output ports, which include a regular repeating structure of optical crossbar switches and interconnections for selectively routing individual ones of entangled photons pairs input to the network to and amongst the outputs; and a control module. The control module is configured to receive a request for entangled photons at the output ports; execute a routing algorithm to determine the state of the switches in the reconfigurable switching network to satisfy the request; and generate and transmit control signals to the switching network in order to set the states of the switches according to the executed routing algorithm. The reconfigurable switching network may be a Bene&#x161; or a banyan-type network architecture.

Method and systems for routing entangled photons to quantum network users via a reconfigurable switch networks of optical crossbar switches

A method for determining a network configuration for the delivery of entangled photons individually to a plurality of users, the network comprising a plurality of inputs, switches, and outputs operatively connected by optical fibers;

Method and system of network switch optimization

A fiber optic system includes a transmitter for transmitting high-speed streaming electrical data to a receiver for receiving the high-speed data. In order to transmit multiple channels in the system at high-speeds, an electrical data signal is converted into multiple optical sub-signals. Each of the multiple optical sub-signals are transmitted at the common wavelength on multi-spatial mode media. The receiver receives the multiple optical sub-signals as a multi-spatial mode optical signal and separates the multi-spatial mode optical signal into branch signals having a common wavelength. The receiver mixes each of the branch signals with optical carrier waves having the common wavelength and converts the branch signals into electrical signals. Digital signal processing is used to recover the data sub-signals which are used to recover the original data signal.

Optical networks using multi-spatial mode media

A quantum key distribution system comprises a source of entangled photon pairs and two single-photon detectors. The source is coupled to each of the single-photon detectors by optical fiber. Operational systems parameters include the efficiency of the first single-photon detector, the efficiency of the second single-photon detector, and the maximum average number of photon pairs per unit time generated by the source. To characterize the operational systems parameters, the transmittances between the source and each single-photon detector are determined. The dark count probability of the first single-photon detector and the dark count probability of the second single-photon detector are determined. The count probability at the first single-photon detector, the count probability at the second single-photon detector, and the coincidence count probability are determined as a function of the optical power from the source. By fitting the values to a set of relationships, the operational systems parameters are computed.

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Millburn, NJ, United States of America

Michael Brodsky