Magiq Technologies, Inc.

Anton Zavriyev

Alexei Trifonov

Caleb A Christensen

Harry N Vig

A Craig Beal

J Howell Mitchell, Jr

Michael LaGasse

Malcolm Cummings

Keun Lee

Alexel Trifonov

Darius Subacius

A method for enhancing a sensitivity of an optical sensor having an optical cavity counter-propagates beams of pump light within the optical cavity to produce scattered light based on Stimulated Brillouin Scattering (SBS). The properties of the pump light are selected to generate fast-light conditions for the scattered light, such that the scattered light includes counter-propagating beams of fast light. The method prevents the pump light from resonating within the optical cavity, while allowing the scattered light to resonate within the optical cavity. At least portions of the scattered light are interfered outside of the optical cavity to produce a beat note for a measurement of the optical sensor. The disclosed method is particularly applicable to optical gyroscopes.

Optical sensors using stimulated brillouin scattering

A method determines a distance with a specified accuracy. The method transmits to an interferometer a test signal oscillating with a test frequency and receives, in response to the transmitting, an interferometric signal formed by interfering the test signal with a delayed signal produced by delaying a copy of the test signal over the distance equal to a path length difference in the interferometer. The test frequency is varying such that the test signal oscillates with different values of the test frequency. The method determines at least two values of the test frequency corresponding to particular values of the interferometric signal by beating the test signal with a reference signal having a reference frequency, wherein a value of the reference frequency is an absolute value predetermined with the specified accuracy. The method determines the distance using the two values of the test frequency.

Distance measurement by beating a varying test signal with reference signal having absolute frequency value predetermined with a specified accuracy

Disclosed is an optical seismic sensor system for measuring seismic events in a geological formation, including a surface unit for generating and processing an optical signal, and a sensor device optically connected to the surface unit for receiving the optical signal over an optical conduit. The sensor device includes at least one sensor head for sensing a seismic disturbance from at least one direction during a deployment of the sensor device within a borehole of the geological formation. The sensor head includes a frame and a reference mass attached to the frame via at least one flexure, such that movement of the reference mass relative to the frame is constrained to a single predetermined path.

Optical seismic sensor systems and methods

Methods for calibrating the modulators in a QKD system () are disclosed. The methods include setting the voltage (V) of Bob's modulator (MB) to a positive value and then adjusting the voltage (V) of Alice's modulator (MA) in both the positive and negative direction to obtain overall relative phase modulations that result in maximum and minimum photon counts (N) in the two single-photon detectors (). Bob's modulator voltage is then set to a negative value and the process repeated. When the basis voltages (V(), V(), V(), V(), V() and V()) are established, the QKD system is operated with intentionally selected incorrect bases at Bob and Alice to assess orthogonality of the basis voltages by assessing whether or not the probability of photon detection at the detectors is 50:50. If not, the modulator voltages are adjusted to be orthogonal. This involves changing Bob's basis voltage (V() and/or V()) and repeating the process until a 50:50 detector count distribution is obtained. The calibration method can be carried out periodically during QKD system operation to ensure optimum or near-optimum operation of the modulators.

Modulator autocalibration methods for quantum key distribution

A two-way actively stabilized QKD system that utilizes control signals and quantum signals is disclosed. Because the quantum signals do not traverse the same optical path through the system, signal collisions in the phase modulator are avoided. This allows the system to have a higher transmission rate than a two-way system in which the quantum signals traverse the same optical path. Also, the active stabilization process, which is based on maintaining a fixed relationship between an intensity ratio of interfered control signals, is greatly simplified by having the interferometer loops located all in one QKD station.

Two-way QKD system with active compensation

A one-way stabilized QKD system () that utilizes a control signal (CS) and a quantum signal (QS) that travel the same path through the system from a first QKD station (Alice) to a second QKD station (Bob). The control signal is detected at Bob and used to stabilize Bob's side of the interferometer against phase variations. The system also includes a polarization control stage () that controls (e.g., scrambles) the polarization of the photons entering Bob. The combination of the polarization control and the active phase stabilization of the interferometer at Bob's end allows for the stable operation of the interferometer when used as part of a one-way QKD system.

Active stabilization of a one-way QKD system

A compact, tunable, high-efficiency entangled photon source system that utilizes first and second periodically poled waveguides rather than bulk media in order to decrease the required pump power by up to several orders of magnitude. The first and second waveguides are arranged in respective arms of an interferometer. Each waveguide has partially reflecting ends, and are each placed on the Z-face of respective periodically poled KTP or LiNBO3 crystals to form respective first and second Fabry-Perot cavities. All waves (pump, idler, and signal) are co-polarized along the z-axis of the crystals. One of the waveguides is followed by a polarization rotator (shown as a half-wave-plate in the Figures) rotating the idler and signal wave polarization by 90 degrees. The outputs from two interferometer arms are combined by a polarization beam combiner and then split by a wavelength multiplexer into two spatially separated time-bin and polarization entangled beams. Another light source, a single frequency stabilized C-band laser (stabilization laser) is used to synchronize cavities spectral modes and phase-lock their outputs.

Compact tunable high-efficiency entangled photon source

A system and method for providing two-way communication of quantum signals, timing signals, and public data is provided. Generally, the system contains a first public data transceiver capable of transmitting and receiving public data in accordance with a predefined timing sequence, a first optical modulator/demodulator capable of transmitting and receiving timing signals in accordance with the predefined timing sequence, a first quantum transceiver capable of transmitting and receiving quantum signals in accordance with the predefined timing sequence, and a first controller connected to the first public data transceiver, the first optical modulator/demodulator, and the first quantum transceiver. The first controller is capable of controlling the transmission of the public data, the timing signals, and the quantum signals in accordance with the predefined timing sequence.

System and method for providing two-way communication of quantum signals, timing signals, and public data

A narrow-band single-photon source () is disclosed, along with a QKD system () using same. The single-photon source is based on spontaneous parametric downconversion that generates signal and idler photons (PS and PI) as an entangled photon pair. Narrow-band signal photons are generated by selectively narrow-band-filtering the idler photons. This results in a non-local filtering of the signal photons due to the time-energy entanglement of the photon pair. Subsequent detection of the filtered idler photon establishes the narrow-band signal photon. The narrow-band single-photon source is particularly useful in a QKD system, wherein the narrow-band signal photons are used as quantum signals to mitigate the adverse effect of chromatic dispersion on QKD system performance.

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Swampscott, MA, United States of America

Anton Zavriyev