BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:G.N. Goltsman DTSTART:20240909T074000Z DTEND:20240909T084000Z DTSTAMP:20260423T005711Z UID:QOART/41 DESCRIPTION:Title: S uperconducting single photon detector: research and applications\nby G .N. Goltsman as part of Quantum Optics and Related Topics\n\n\nAbstract\nD uring last twenty years\, a new generation of superconducting detectors ba sed on hot-electron-phenomena was developed. These sensors have already de monstrated performance that makes them devices-of-choice for many terahert z\, infrared and optical applications. The development of compact helium-f ree cryocoolers together with effective sources of terahertz\nand infrared radiation greatly expanded the field of application of superconducting de tectors including astronomy\, medicine\, security and quantum communicatio ns\, and made them friendly in use. To date\, due to the growing interest\ , the market for superconducting devices is gradually expanding\, as evide nced by the emergence of small companies engaged in the development\, impr ovement and commercialization of superconducting devices. \nOne such devic e is the superconducting nanowire single-photon detector (SNSPD or SSPD). SNSPDs combine high detection efficiency\, low dark count rate\, and high temporal resolution in a single device in visible and near IR range. SNSPD s have been successfully employed for classical and quantum optics applica tions ranging from optical time domain reflectometry (OTDR)\, light detect ion and ranging (LiDAR)\, space-to-ground communications\, quantum dot pho tonics\, quantum key distribution to experiments with indistinguishable an d entangled photon pairs and applications in the life sciences. \nFew year s ago\, a fully integrated circuit including a single photon source (carbo n nanotube)\, detectors (SNSPDs) and Si3N4 waveguides has already been imp lemented on a chip. Going beyond such proof-of-principle concepts\, the re alization of large scale QPICs is expected to have profound impact on scie nce and technology\, material engineering\, as well as quantum information processing including quantum computing\, simulation and metrology.\nIt ha s recently been shown that the nanosize of the current-carrying strip is n ot a necessary attribute for single-photon detection. Using a kinetic-equa tion approach\, the dynamics of electrons and phonons in current-carrying superconducting strip with a current close to the depairing current after the absorption of a single photon of the near-infrared or optical range wa s studied. Second\, it has been experimentally demonstrated that single-ph oton detection is indeed achieved in micrometer-wide NbN bridges biased by a direct current close to the experimental critical current\, which is es timated to be at least 50% of the theoretically expected depairing current . These results offer an alternative to the standard superconducting singl e-photon detectors\, based on nanometer-scale nanowires implemented in a l ong meandering structure. The results are consistent with improved theoret ical modeling based on the theory of nonequilibrium superconductivity\, in cluding the vortex-assisted mechanism of initial dissipation. To think abo ut practical devices\, we choose to work with wide wires fabricated with p hotolithography rather than narrower wires commonly fabricated with e-beam lithography. These wider wires consume more area\, which is problematic i n large integrated systems. We find that elimination of even a\nsingle e-b eam lithography step greatly simplifies fabrication process. \nFurther dev elopment of SSPDs associated with the implementation of complex integrated photonic (PICs) and quantum photonic integrated circuits (QPICs) on a sin gle chip. Integrated circuits are resistant to mechanical vibrations and t emperature fluctuations\, they do not require long alignment procedure and can be easily scaled. To date\, integrated SNSPDs have been implemented o n various material platforms\, such as silicon on insulator (SOI)\, galliu m arsenide (GaAs)\, silicon nitride (Si3N4) and polycrystalline diamond. E ach platform has its advantages and disadvantages\, so further development takes place in parallel. Despite the fact that all the building blocks fo r a fully-functional QPIC\, including single-photon sources\, detectors an d passive circuits\, have been demonstrated\, full integration of all the components on a single chip is still a somewhat challenging and complicate d task.\n LOCATION:https://researchseminars.org/talk/QOART/41/ END:VEVENT END:VCALENDAR