Project: Smart photon detection system based on NbTiN superconducting detectors

SNaPy (Superconducting NAnowires Photodetection) is an ambitious two years market-oriented project aiming at the development of a smart photon detection system based on NbTiN (Niobium Titanium Nitride) superconducting nanowires optimized for detection at telecom wavelengths._x000D_Single photon detection at 1.31um and 1.55um is required in an increasing range of applications such as QKD (Quantum Key Distribution), quantum optics, OTDR (Optical Time DoCO Reflectometry), LIDAR-based measurements (LIght Detection And Ranging), spectroscopy or IC (Integrated Circuits) failure analysis. A common and urgent need for these applications is the asynchronous detection of high rates incoming photons. In the field of QKD for instance, free-running mode is essential in entanglement based technologies as most photon pair sources require asynchronous detection schemes._x000D_Superconducting nanowire single-photon detector (SNSPD) is emerging as a highly promising infrared single-photon detector technology. The wire is cryogenically cooled to 2-4K below its critical temperature Tc. Below Tc, the wire is superconducting and has zero electrical resistance. Above Tc, the wire is in its normal state and has a relatively high resistance. The wire is biased with a DC current slightly below the critical current, above which the superconductivity breaks down. A photon absorption by the wire results in a localized region known as a hot spot within which the temperature of the electrons is sufficiently elevated that the superconductivity is disrupted and the material reverts to the normal state. A small amplitude voltage pulse reflecting the photon arrival is then created. The use of nanowires that cover reduced area of typically 10um in diameter comes with tricky constraints for light coupling from a 9um core single mode fiber. _x000D_The SNaPy project is based on outstanding results recently obtained by the Quantum Transport Group at TU-Delft (TUD). NbTiN SNSPDs have been fabricated on silicon substrates and micromechanically coupled to a single mode fiber. Detection efficiency larger than 20% at DCR of 1kHz and timing resolution of 60ps have been demonstrated._x000D_The SNaPy project aims, not only at the industrialization of the achieved results, but at a significant improvement of the optical performance, both at the device and fiber coupling levels. The fabrication will be carried out with strict reliability and costs constraints and the device optimization market-oriented. A complete photon detection system will be developed including cost-effective cooling apparatus, core electronics dedicated to the operation of NbTiN SNSPDs and a smart electronic module providing application-oriented functionalities. The CO technical objectives related to the project are: _x000D_- the routine cost-effective fabrication of NbTiN superconducting meanders optimized for 1.31um and 1.55um,_x000D_- the design and validation of a self-alignment technique for the coupling of a single mode fiber allowing the achievement of a detection efficiency larger than 25%,_x000D_- the tests of innovative structures with enhanced efficiency and targeting 50% at telecom wavelengths,_x000D_- the construction of a reliable optical sub-system meeting high frequencies operation and electromagnetic compatibility, _x000D_- the design and fabrication of a cost-effective low-leakage cryogenic insert suited to most L-He (Liquid Helium) storage dewars,_x000D_- the design and fabrication of a closed-cycle cryocooler intended for a dual-channel optical sub-system,_x000D_- the development of a core electronics providing outstanding bias current stability, normal-to-superconductive reset functionality and low jitter amplification,_x000D_- the design of a smart dual-channel electronic module including, in particular, high-frequency counters, correlators, a post-gating function and a graphical user interface. _x000D_The Consortium brings together two complementary Ps: a swiss SME, ID Quantique (IDQ), and the Quantum Transport Group of the Delft University of Technology. Each P has a top-ranking expertise in the fields required to make the project a technical and a commercial success. IDQ is present on the instrumentation market since 2001. Thanks to a wide customer basis, IDQ is well aware of the market demands and emerging applications. Build around a team of physicists, hardware, software and tests engineers, IDQ has a leading expertise in products development for the instrumentation market. For years, the Quantum Transport Group of TU-Delft has been employing in-house facilities for the nanofabrication of opto-electronic devices. Besides its expertise in the fabrication of SNSPDs, the group has a perfect understanding of potential applications and a crucial knowledge in cryogenics in general. In addition to the Consortium, the "Superconducting single photon detectors" group lead by Robert Hadfield at Heriot Watt University will bring its expertise in closed-cycle cryocoolers as a subcontractor.

Acronym	SNaPy (Reference Number: 6623)
Duration	01/10/2011 - 30/11/2013
Project Topic	A dual-channel smart photon detection system based on high-efficiency NbTiN superconducting detectors is developed. It includes the necessary bias/amplification electronic circuits, the cooling apparatus and provides smart functionalities required by current applications at telecom wavelengths.
Project Results (after finalisation)	We have made superconducting nanowire single photon detectors and studied their fabrication recipes, steps were taken to reduce the fabrication costs. Photolithogrpahy was explored to produce electrical contacts at lower costs. Detectors were transfered to ID quantique for testing and evaluation.
Network	Eurostars
Call	Eurostars Cut-Off 6

Project partner

Number	Name	Role	Country
1	Delft University of Technology	Partner	Netherlands