Superconducting Nanowire Single Photon Detector (SNSPD) integrated with optical circuits

Transcription

1 Superconducting Nanowire Single Photon Detector (SNSPD) integrated with optical circuits Marcello Graziosi, ESR 3 within PICQUE (Marie Curie ITN project) and PhD student marcello.graziosi@ifn.cnr.it Istituto di Fotonica e Nanotecnologie IFN-CNR Quantum Optics Group, Dipartimento di Fisica, Sapienza Università di Roma Supervisor at Sapienza: Prof. Paolo Mataloni Supervisor at IFN-CNR: Dr. Roberto Leoni

2 Outline PICQUE and IFN-CNR Motivation Approaches for SNSPD optical integration SNSPD fabrication process SNSPD characterization and performances Conclusion and future steps

3 What s PICQUE? Photonic Integrated Compound Quantum Encoding (Sept 2013 Aug 2017) is a Marie Curie Initial Training Network (ITN) 10 full partners 8 associated partners 7 different European countries 11 Early Stage Researcher (ESR) PhD 7 Experienced Researcher (ER) Post-docs Scientific topic of PICQUE Development of the basic components of a photonic quantum processor Applications of integrated quantum photonics in the Quantum Information Science PICQUE Coordinator: Prof. Fabio Sciarrino fabio.sciarrino@uniroma1.it PICQUE Project Manager: Giuliana Pensa giulianapensa@gmail.com

4 NADIR group and IFN (Rome Unit) technologies Nanostructures, quantum-devices and detectors (NADIR) 3 Senior researcher, 3 Staff researchers 1 Fellow Researcher, 1 PhD student Working mostly on on SNSPDs Dr. Roberto Leoni Senior researcher, (my supervisor) Dr. Alessandro Gaggero Fellow researcher Dr. Francesco Mattioli Staff researcher Marcello Graziosi PhD student IFN - CNR Roma, via Cineto Romano, 42, ROMA, Some of the technologies available at IFN: Thin film deposition (e-beam vapor deposition, sputtering, etc.) Electron beam lithography and optical lithography Wet etching, RIE and deep RIE Nano-characterization instruments (AFM and SEM) Cryostats for electrical characterization at cryogenic temperature

5 Single Photon Detector for Quantum Information Quantum Walk for Bosonic and Fermionic statistic Boson Sampling Photonic Quantum processor Quantum cryptography such as Quantum Key Distibution (QKD) Why SNSPD? Telecom wavelength 1550 nm High efficiency ( > 70% (even > 90%)) Low dark count (few hundreds of Hz) No need to be gated Low time jitter ( < 40 ps) and Gaussian distribution Short dead time ( 10 ns) A.Crespi et al., Nature Photonics, vol.7 (2013) L.Sansoni et al., Physical Review Letters, 108 (2012) H.Takesue et al., Nature Photonics, vol.1 (2007)

6 Optical Integration SNSPDs integration on optical waveguides 1. Development and integration of SNSPD arrays in photonic circuits 2. Only one readout electrical circuit for the detector arrays SNSPDs stand-alone system for highly efficient optical fiber coupling

7 What are SNSPDs? Devices based on Si technology (cleanroom fabrication processes) L k Photon R d Photon absorption breaks Cooper pairs NbN 5 X 80 nm 2 Superconductivity is locally broken

8 Fabrication process 1. Si wafer (starting point) 2. Optical cavity thermal growth of λ 4 thickness ( 270 nm) of SiO 2 3. Superconductive layer sputtering at 750 C and 10 7 mbar 4. Lift off process for Au electrical pad 5. EBL lithography and RIE for patterning the NbN meander Au pads 1 mm NbN 5 nm SiO nm Si wafer 400 um Au 60 nm Ti 10 nm NbN 5 nm SiO nm Si wafer 400 um NbN meander 13 μm- diameter Au pads Au 60 nm Ti 10 nm NbN 5 nm H S Q SiO nm Si wafer 400 um 2 μm

9 Lollipop shape for optical fiber coupling Deep RIE to Lollipop shape the detector Optical Fiber All the wafer thickness is etched Lollipop 200u m Lollipop Top illuminated SNSPDs standalone system for highly efficient optical fiber coupling Au 60 nm Ti 10 nm NbN 5 nm H S Q SiO nm Si wafer 400 um NIST approach, Miller et al, OE 2011

10 Waveguides fabrication SOI wafer (Si waveguides on Silica) 500 nm wide X 220 nm thick SU8 (epoxy-based photoresist) waveguides on glass Next step will be to fabricate SNSPD on top of the waveguides

11 Characterization at cryogenic temperature 1. Low Frequency (LF) measurements for NbN nanowires quality testing (different nanowires width from 100 nm to 5.0 μm) 2. High frequency (HF) measurements for analyzing SNSPD performance LF setup SNSPD equivalent circuit Device electrical characterization at T 2.5 K by a Gifford-McMahon (GM) cryogen-free cryostat

12 Low frequency measurements NbN on SiC Different critical temperatures for different substrates I c = 55 μa w = 100 nm NbN on SiN Critical density current I c = 15 μa w = 100 nm I c = 150 μa w = 1 μm

13 High frequency measurements DC+RF arm DC arm RF arm Bias tee SNSPD Polarizer Attenuatore ottico Fibra Laser in continua (1.550 um) DC DC arm DC+RF arm Bias tee RF arm 13dB 13dB Oscilloscope Or Counter Electrical Setup SNSPD biased in DC I bias < I c Bias tee to split DC bias from pulse 2 amplifier at 13 db Optical Setup Laser at λ = μm Optical attenuator to decrease optical power at 10 6 photons sec 0.5 mw must be attenuated 100 db

14 Efficiency and Dark Count IV curve I c 21 μa Systen quantum efficiency SQE % Dark Count Rate Results from Single Quantum's SNSPDs (Delft, Netherlands) Amplified SNSPD pulse

15 Conclusion and next step Main achievement so far Fabrication and quality characterization of SNSPD on different material Development of cleanroom fabrication process to have a SNSPDs stand-alone system for highly efficient optical fiber coupling Ongoing and future steps To complete the realization of HF electrical setup for optical characterization SNSPD integration on SU8 and SOI waveguides Array of SNSPDs with only one readout electrical circuit Final step (hopefully ) Quantum Information experiment with SNSPDs fabricated by us at IFN-CNR Rome