NASA Glenn Research Center’s quantum metrology approach is to combine measurements and models. Measurement results and models are subsequently integrated with NASA’s aerospace competency needs to provide an understanding of how spaceflight components work together in quantum network architectures. Trade studies and device measurements are performed within NASA’s Quantum Metrology Laboratory (NQML) whereas dynamic quantum network modeling occurs via the NASA Quantum Communications Analysis Suite (NQCAS) simulation tool. In illustrating the synthesis of the network model and metrology for quantum network development, we have focused on the evaluation of a degenerate Spontaneous Parametric Down Conversion (SPDC) source. Here we present an overview of Hong-Ou-Mandel and Joint Spectral Intensity measurements of the degenerate SPDC source. Results of these experiments are input into NQCAS to evaluate source suitability for entanglement swapping. This demonstrates the technology development approach of coupling of quantum measurement and free space quantum network models.
A periodically poled MgO – doped LiNbO3 (MgO:LN) non-degenerate photon pair source is utilized for spontaneous parametric down-conversion of 532 nm photons into time-energy entangled pairs of 794 and 1614 nm photons. The entangled photons are separated using previously detailed sorting optics, such that each wavelength is independently directed through one of two modified Mach-Zehnder interferometers – also known as a Franson interferometer – after which they are fiber-optically guided to high-efficiency photon detectors. Output from the detectors is sent to a high resolution time tagger, where coincidences between the entangled photons are recorded. By varying the length of the long path in one Mach-Zehnder interferometer, it is possible to observe high visibility sinusoidal fringes in the measured coincidence rates (while no variation is seen in single photon detection rates). These fringes – due to interference between the photon probability amplitudes – are indicative of a violation of the Bell inequality, and confirm inconsistencies with local hidden variable theory for the correlations of the time-energy entangled photon pairs.
KEYWORDS: Sensors, Nanowires, Silicon, Avalanche photodetectors, Photodetectors, Quantum efficiency, Single photon detectors, Superconductors, Time correlated photon counting, Signal to noise ratio
Time-energy entangled photon pairs are created by a system consisting of a 1064 nm pump diode laser that is fiber coupled to a high generation rate photon pair source. The source is a dual element periodically poled Magnesium Oxide doped Lithium Niobate (MgO:LN) waveguide that upconverts 1064 nm photons to single 532 nm photons in the first stage. In the second stage, the green photons are down converted to time-energy entangled photon pairs at 794 nm and 1614 nm. The output photon pairs are guided by fiber to sorting optics where they are separated and sent into high-efficiency photon detectors. In particular, the 1614 nm photons are detected by a superconducting nanowire with efficiency near 85% and dead time less than 30 ns. Detector output electrical signals are sent to a time tagger with bin resolution as narrow as 25 ps for coincidence counting. The ultimate goal of this setup is to demonstrate a single-source, high efficiency, high data rate, low noise, quantum communication system to enable Earth-space quantum networks. Test results that characterize the time-energy entangled photon pair creation rates of our source will be presented, via measures of accidental and true coincidence rates versus pump current. To reduce noise (accidentals) as much as possible, and for better understanding of our overall quantum system path-efficiency, studies of fluorescence caused by our pump’s 1064 nm and 532 nm photons will be investigated and discussed. Finally, characteristic measurements of our superconducting nanowire detector, such as dead time and detection efficiency versus electrical bias, will be offered. Please verify that (1) all pages are present, (2) all figures are correct, (3) all fonts and special characters are correct, and (4) all text and figures fit within the red margin lines shown on this review document. Complete formatting information is available at http://SPIE.org/manuscripts Return to the Manage Active Submissions page at http://spie.org/submissions/tasks.aspx and approve or disapprove this submission. Your manuscript will not be published without this approval. Please contact author_help@spie.org with any questions or concerns.
Entangled photon pairs are created by a system consisting of a 1064 nm pump diode laser that is fiber coupled to a high generation rate photon pair source. The source is a dual element periodically poled potassium titanyl phosphate (KTP) waveguide that up-converts 1064 nm photons to single 532 nm photons in the first stage. In the second stage, the green photons are down converted to energy entangled photon pairs at 800 nm and 1600 nm. The output photon pairs are guided by fiber to sorting optics where they are separated and sent into high-efficiency photon detectors. In particular, the 1600 nm photons are detected by a superconducting nanowire with efficiency over 60% and dead time less than 50 ns. Detector output electrical signals are sent to a time tagger with bin resolution as narrow as 25 ps for coincidence counting. The ultimate goal of this setup is to demonstrate a singlesource, high efficiency, high data rate, quantum communication system to enable Earth-space quantum networks. Of particular interest is a source of entangled photons that is amenable to utilization in aircraft and spacecraft under rigorous flight and environmental conditions. Test results that characterize the entangled photon pair creation and detection capabilities of our system will be presented.
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