Superconducting Nanowire-Single Photon Detectors (SNSPDs) have emerged as the highest-performing single-photon detectors, with detection efficiencies reaching 98%, maximum count rates over 1 Gcount/s, and the ability to distinguish between single-photon and multi-photon events. SNSPDs have enabled our group to demonstrate loophole-free tests of Bell’s inequality and device-independent randomness expansion. In this talk I will discuss a new scheme using SNSPDs for high-rate, high-fidelity entanglement distribution between remote nodes of a quantum network. The scheme uses a high-quality heralded entangled source and all-optical quantum repeaters. I will discuss requirements for the SNSPDs and strategies for achieving interferometric stability across the network. Both will be crucial for achieving high-fidelity entanglement distribution at high rates.
Quantum optical approaches to biological measurement could enable unprecedented sensitivity, specificity, and resolution with minimal sample perturbation. Additionally, quantum optics provides new “knobs to turn” in imaging and spectroscopy that are not approachable with classical means. One such example is through entangled photons, in which groups of photons have properties that are intrinsically and inseparably linked. In this presentation, I will provide an introduction to entangled light applications, our experimental work in two-photon absorption with entangled light, and our experimental work establishing that even post-traversal through micrometers and millimeters of biological tissue/media, time-energy entangled light can maintain this unique linkage.
Entangled two-photon absorption (e2PA) employs advantages of classical two-photon absorption techniques while operating in a linear excitation regime at low fluxes and potentially having greatly enhanced absorption probabilities. A major challenge in measuring the e2PA cross section, σe2PA, is to discriminate e2PA from one- photon losses. Carefully designed transmittance measurements are required to distinguish the two mechanisms. For example, the e2PA signal should depend on the time delay between photons within an entangled pair (in contrast to one-photon losses). Here we present an experimental system implementing this characterization. We perform transmittance experiments for Zinc-tetraphenylporphyrin (ZnTPP) in toluene solution. We use entangled photons produced via spontaneous parametric downconversion at 810 nm wavelength as an excitation source. We show that the change in transmittance associated with e2PA in the sample is less than 1% in our experiment. From our measurements we conclude ZnTPP's σe2PA ≤1:7 x 10-19 cm2.
We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.
We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array, as well as characterization measurements are discussed.
Light emission at 1.54 μm from an Er-doped amorphous silicon nitride layer coupled to photonic crystal resonators
and plamonic arrays is studied. We observe the cavity resonances at cryogenic and room temperatures and under
varying optical pump powers. The results demonstrate that small mode volume, high quality factor resonators
enhance Er absorption rates dramatically at the cavity resonance. Photonic crystal cavity resonances exhibit
linewidth narrowing with pump power at cryogenic temperatures, signifying absorption bleaching and partial
inversion of the Er ions. In addition, we fabricate periodic metal-insulator-metal plasmonic structures with a
simple bottom-up fabrication technique. We observe a factor of 10 increase of Er emission coupled to plasmonic
structures.
We report on the photoresponse mapping of nanowire superconducting single-photon detectors using a focal spot
significantly smaller than the device area (10 μm x 10 μm). Using a solid immersion lens we achieve a spot size of 320
nm full-width half maximum onto the device at 470 nm wavelength. We compare the response maps of two devices: the
higher detection efficiency device gives a uniform response whereas the lower detection efficiency device is limited by a
single defect or constriction. A second optical setup is used to simultaneously image and measure the photoresponse of
the lower detection efficiency device, allowing the constriction location to be pinpointed.
We report use of a niobium nitride superconducting single-photon detector in a time-correlated single-photon counting experiment. The detector has a timing jitter of 68 ± 3 ps full width at half maximum with a Gaussian temporal profile. The detector's dark count rate and detection efficiency can be tuned by adjusting the bias current applied to the device. Typical values include a detection efficiency of ~1-2% and a dark count rate below 100 Hz. We use this detector to measure time-resolved photoluminescence at wavelengths up to 1650 nm, well beyond the range of conventional silicon detectors. We also use this superconducting detector to measure the emission of a quantum dot single-photon source.
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