Shellee D. Dyer

Strong Loophole-Free Test of Local Realism

We performed an loophole-free test of Bells inequalities. The probability that local realism is compatible with our results is less than 5.9×10^-9.

Low-coherence interferometric measurements of the dispersion of multiple fiber Bragg gratings

We show that the dispersion of multiple fiber Bragg gratings can be obtained from a single low-coherence interferometric measurement. The individual gratings can be identified either from the spatial separation of the interferometric signatures or from the unique wavelength-reflection bands of the gratings.

High-resolution single-mode fiber-optic distributed Raman sensor for absolute temperature measurement using superconducting nanowire single-photon detectors

We demonstrate a distributed fiber Raman sensor for absolute temperature measurement with spatial resolution on the order of 1 cm at 1550 nm wavelength in a single-mode fiber using superconducting nanowire single-photon detectors. Rapid measurements are shown, with less than 60 s integration period, allowing the demonstration of temperature evolution in an optical fiber recorded at over 100 resolvable, 1.2 cm spaced positions along the fiber simultaneously. This distributed sensor has potential application as a primary reference standard, in which high-accuracy, high-spatial-resolution temperature measurements can be obtained without the need for a separate temperature calibration standard.

High-efficiency, ultra low-noise all-fiber photon-pair source

We demonstrate an all-fiber photon-pair source with the highest coincidence-to-accidental ratio (CAR) reported to date in the fiber-optic telecom C-band. We achieve this through careful optimization of pairproduction efficiency as well as careful characterization and minimization of all sources of background photons, including Raman generation in the nonlinear fiber, Raman generation in the single-mode fiber, and leakage of pump photons. We cool the nonlinear fiber to 4 K to eliminate most of the Raman scattering, and we reduce other noise photon counts through careful system design. This yields a CAR of 1300 at a pair generation rate of 2 kHz. This CAR is a factor of 12 higher than previously reported results in the C-band. Measured data agree well with theoretical predictions.

Fundamental limits in fiber Bragg grating peak wavelength measurements

We discuss the fundamental limits of fiber Bragg grating (FBG) wavelength metrology. High-accuracy wavelength measurements are critical for FBG strain sensors because a wavelength measurement uncertainty as small as 1 pm leads to an uncertainty of nearly 1 microstrain. We compare the measurement uncertainties for several common wavelength measurement systems, including tunable laser, optical spectrum analyzer (OSA), and interferometric. We show that when using an OSA it is difficult to achieve a measurement uncertainty better than 10 pm, and if the OSA is not accurately calibrated to a known wavelength reference, then the wavelength measurement uncertainty can be as large as 1 nm. We describe the uncertainties involved in determining peak and/or centroid wavelength from a measured data set. We also discuss calibration references for FBG sensor interrogation units. Wavelength references that are based on molecular absorption lines are often an excellent choice for FBG sensor calibration. However, some interrogation units require a wavelength reference unit based on narrow reflection lines rather than absorption lines. We investigated the application of athermally packaged FBGs as wavelength references, but we found that their wavelengths will drift with time and can undergo large jumps. We concluded that it is difficult to achieve stability better than 4 pm/year in athermally packaged FBGs.

Fast and accurate low-coherence interferometric measurements of fiber Bragg grating dispersion and reflectance.

We demonstrate fast and accurate measurements of fiber Bragg grating dispersion and spectral reflectance using low-coherence interferometry. Both dispersion and spectral reflectance are obtained in less than 60 seconds, rendering the results immune to errors caused by temperature variations and instrumental drift. To examine the accuracy of the low-coherence technique, we compare the results with independent measurements and demonstrate an agreement better than 1.5 ps for dispersion and 25 pm for spectral reflectance wavelength.

High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films

We report on MoSi SNSPDs which achieved high system detection efficiency (87.1 ± 0.5% at 1542 nm) at 0.7 K and we demonstrate that these detectors can also be operated with saturated internal efficiency at a temperature of 2.3 K in a Gifford-McMahon cryocooler. We measured a minimum system jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.3 ± 0.1%. The performance of MoSi SNSPDs at 2.3 K is similar to the performance of WSi SNSPDs at < 1 K. The higher operating temperature of MoSi SNSPDs makes these devices promising for widespread use due to the simpler and less expensive cryogenics required for their operation.

High-brightness, low-noise, all-fiber photon pair source.

We demonstrate an all-fiber photon pair source for the critical telecom C-band. We achieve high pair generation rates in excess of 10 MHz while maintaining coincidence-to-accidental ratios (CARs) greater than 100. This is one of the brightest and lowest-noise photon pair sources ever demonstrated. We achieve the high pair rate through CW-pumped spontaneous four-wave mixing in dispersion-shifted fiber. We achieve the high CAR by cooling the fiber to 4 K to suppress the Raman generation and detecting the photons with low jitter and low dark count superconducting single-photon detectors.

Demultiplexing of interferometrically interrogated fiber Bragg grating sensors using Hilbert transform processing

The peak reflectance wavelengths of gratings with reflectance maxima separated by less than 2 nm can be accurately determined through a demultiplexing method based on Hilbert transforms of interferograms. We demonstrate a wavelength demultiplexing of three fiber Bragg gratings (FBGs) with less than 4 pm crosstalk and repeatability and less than 19 pm uncertainty. We anticipate that a large number of gratings can be demultiplexed with a single broadband source and a single receiving interferometer, provided that the interferogram is sampled at accurate intervals slightly above the Nyquist rate.

Quantum teleportation over 100 km of fiber using highly efficient superconducting nanowire single-photon detectors

Quantum teleportation is an essential quantum operation by which we can transfer an unknown quantum state to a remote location with the help of quantum entanglement and classical communication. Since the first experimental demonstrations using photonic qubits and continuous variables, the distance of photonic quantum teleportation over free space channels has continued to increase and has reached >100 km. On the other hand, quantum teleportation over optical fiber has been challenging, mainly because the multi-fold photon detection that inevitably accompanies quantum teleportation experiments has been very inefficient due to the relatively low detection efficiencies of typical telecom-band single photon detectors. Here, we report efficient quantum teleportation over optical fiber using four high-detection efficiency superconducting nanowire superconducting single-photon detectors (SNSPD) based on MoSi. These SNSPDs make it possible to perform highly-efficient multi-fold photon measurements, allowing us to confirm that the quantum states of input photons were successfully teleported over 100 km of fiber.