Detecting single photons. Andrea Fiore

Transcription

1 Detecting single photons

2 Why single-photon detectors? Measure "very efficient" nonlinear frequency conversion... A PhD student "under Rosencher's rule": Will I ever get a few photons and my thesis? Wikipedia Solution n. 1: Change field and work on lasers...

3 Single-photons again... "Les photons... présentent un certain nombre de comportements paradoxaux" Emmanuel Rosencher, Optoélectronique, Masson ed. "We estimate the potential market for Quantum Cryptography is likely to reach $1 billion per annum" Bob Gelfond, MagiQ Corporation, New York id201 Singlephoton APD Presently limits system performance Let's get this fixed for good: Single-photon detectors

4 Nanowire Superconducting Single-Photon Detector NbN Golts'man et al., APL (2001) + V - R hs T>T C J>J C t w 3-10nm I~I C nm

5 Meander SSPDs 100nm 150nm 5μm 5μm Marsili et al., Optics Express 2008 Nanofabrication: CNR-IFN Rome

6 SSPD operation Bias T + V - i Voltage (a.u.) ns Time(ns) 1000x more sensitive than InGaAs APDs at nm Can run in continuous mode, with counting rates>80 MHz Timing resolution <30 ps Dominant technology for single-photon detection in the telecom range

7 Photon-number-resolving detectors Meander SSPDs do not resolve the photon number Time Light Single-φ PNR det. Voltage Time Bias T + V -? i R hs R hs R L PNR functionality needed in many quantum protocols

8 Parallel-Nanowire Detector Bias T + V - Output pulse photon number if: N. wires >> N. photons Other wires do no shunt switching wire

9 + V OUT R A - Electrical equivalent circuit S l Rhs S l S l Rhs S l S l Rhs S l S l + - I RL I b I b I b Rhs Lkin V b I b R0 Lkin Lkin Lkin R0 R0 R0

10 Fabricated PNDs R R Film growth and EPFL,

11 Experimental PND output PND output voltage under illumination with laser pulses: Simulation: Experimental I out (a.u.) Time (ns) Divochiy et al., Nature Photonics, 2008

12 Proving the PNR functionality Pulse height statistics with a sampling scope: Voltage 4 wires PND-R 66 nw Most promising technology for fast and sensitive PNR detection in the telecom range Time Collaboration with MSPU Detected pulses follow Poissonian statistics Proof of PNR operation Divochiy et al., Nature Photonics, 2008

13 Curiosity-driven: A singlephoton nanodetector? Detection mechanism in SSPDs is nanoscale, but meander SSPDs usually cover large areas We lose spatial information 30 nm Near-field imaging Sub-λ quantum imaging Det. Direct detection in near-field Smaller detector Lower noise D'Angelo et al., Phys. Rev. Andrea Lett Fiore

14 Nanoscale single-φ detector QE 50 nm < 30 nm active area possible

15 n-sspd performance Proof of single-φ detection: Counts (s -1 ) I b =8.5μA 50 nm Slope=0.99 Data Linear fit Light power (a. u.) Diffraction spot of microscope objective: Bitauld et al., Nano Lett Able to image submicrometer (down to 500 nm) features with single-photon sensitivity Expected detector resolution nm

16 Nanoscale PNR? High bias current: Single-φ response

17 Nanoscale PNR detection Count rate (s -1 ) I b =17μA s=1.9 I b =14.4μA Low bias current: s=2.98 ( n)-photon detector I b =11.2μA s=3.99 I b =9.2μA C n s=1.03 s Average n. photons/pulse Linear Fits

18 Multiphoton imaging Detection prob. 1,2 1 0,8 0,6 0,4 N=1 N=2 N=3 N=4 FWHM (μm) N=1: FWHM=0.9 μm N=4: FWHM=0.41 μm FWHM S = N 1 N 0, Position (μm) Increased contrast Bitauld et al., Nano Lett Increased resolution possible with entangled light

19 Summary Photodetection in superconducting nanowires opens new avenues in single- and multi-photon detection PNRs detection possible at telecom wavelengths Nanoscale detection opens the way to nanoscale quantum photonics Integration with GaAs-based (quantum) photonics possible

20 Acknowledgements Contributors: - F. Marsili, D. Bitauld, S. Jahanmiri Nejad, J.P. Sprengers, D. Sahin, G.J. Hamhuis, R. Notzel (TU Eindhoven) - A. Gaggero, R. Leoni, F. Mattioli (CNR Rome, Italy) - F. Lévy, R. Sanjines (EPF Lausanne) Funding: EU-FP6 SINPHONIA and FP7 QUANTIP Dutch STW-Vici, Swiss NCCR Quantum Photonics