Time delay of superconducting stripe when jjc in the sidewalks

1
GHz-Rate Superconducting Photon Counting Detector

• Verevkin, R. Sobolewski
• Department of Electrical and Computing
  Engineering
• and Laboratory of Laser Energetics
• University of Rochester, Rochester NY 14627
• G. N. Goltsman
• Moscow State Pedagogical University

NIST Single Photon Workshop April 1, 2003
2
Acknowledgements

• Dr. A.Semenov (DLR, Berlin, Germany)
• Dr. C. Williams (Corning, Corning NY)
• J. Zhang, X. Zheng, Y. Xu,A. Pearlman, UR
• O.Okunev, G. Chulkova, A. Lipatov, A. Korneev,
  N.Kaurova, V. Drakinsky, K. Smirnov, B. Voronov
  (MSPU, Moscow)
• - Dr. D. Nicholson, AFRL/IFGC, Rome, NY
• Dr. K. Wilsher, Dr. W. Lo, NPTest, San Jose, CA
• - Support NSF, AFOSR, ONR, NPTest Inc.

3
Outline
Introduction and Motivation NbN Superconducting
Single-Photon Detector - how does it work? -
performance and experimental results Applications
- quantum cryptography and communications
- noninvasive testing of VLSI
chips Conclusions
4
Why superconducting detectors are promising?

• Semiconductors
• One optical photon creates only one
• electron-hole pair
• (typical bandgap 1-2 eV)
• At low temperatures,
• relaxation and response times are long in APDs

• Superconductors
• One optical photon creates 1001000 excited
  quasiparticles
• (superconducting gap
• 2 meV for NbN)
• b) Relaxation is ultrafast
• even at low temperatures

Low temperature environment reduces background
noise and thermal fluctuations responsible for
dark counts.
5
(No Transcript)
6
Hotspot formation in a thin superconducting
metallic film occurs upon the absorption of a
photon
- Initial hotspot forms due to electron
thermalization and the generation of a large
number of excited quasiparticles (quasiparticle
avalanche process). - The hotspot grows due to
the quasiparticle diffusion and electro-phonon
secondary excitation. - The hotspot collapses
due to the quasiparticle recombination and
out-diffusion.
7
(No Transcript)
8
(No Transcript)
9
(No Transcript)
10
Meander-structured thin-film NbN SSPDs
10x10 mm2 meander-type 10-nm-thick SSPD structures
early devices
later devices
Due to the device geometry, some radiation flux
in not absorbed. Intrinsic Quantum Efficiency
(QE) is larger than experimental Detection
Efficiency (DE)
11
Inter-digitated structure of thin-film NbN SSPD
Tc of 3.5-nm-thick NbN SSPD is gt10 K
3.5-nm-thick device with 0.5 fill factor
12
SSPD experimental setup
13
SSPD response versus the incident photon flux
A
20000 photons/pulse 2400 photons/pulse 2400
photons/pulse 80 photons/pulse 1
photon/pulse 1 photon/pulse
In the single-photon counting regime, the number
of photoresponse pulses is proportional to the
incident photon flux.
B
C
D
E
F
Illumination source 100-fs pulses, 810-nm
wavelength, 82-MHz repetition rate
14
Photoresponse statistics of a 3.5-nm-thick NbN
SSPD illuminated by photons with810-nm and
1540-nm wavelengths
15
Hotspot size is a function of incident photon
energy (wavelength)
16
Detection efficiency is an exponential function
of the SSPD bias current
10-nm-thick device
2
17
Spectral dependence of the detection efficiency
(DE) for 3.5-nm and 10-nm SSPDs
10 x 10 mm2 devices
SSPDs are effective from UV to IR
Intrinsic QE is approx. 30 larger than
experimental DE
For visible-light photons QE reaches 100
18
Dark counts and NEP for 3.5-nm-thick SSPD
19
SSPD jitter measurements
The system jitter is 35 ps with Tsunami
TiSapphire laser, which includes contributions
from the laser the amplifier. Signal FWHM lt 150
ps, negative voltage due to quasiparticle recombin
ation is observed.
20
1-GHz-rate photoresponse trainof a 3.5-nm-thick
NbN SSPD
(Pritel Inc. fiber laser)
21
SSPD Counting speed is above 2GHz
Jitter is lt18 ps at 775 nm and 1550 nm fiber
Pritel Mode-locked laser
22
Quantum Cryptography (QC) based on single-photon
communication assures unconditional security
Bob (Receiver)
Alice (Transceiver)
from Simon Benjamin, Science 290, 2273 (2000)

• Unconditionally secret, quantum key distribution
  is possible in actual physical environments due
  to Heisenberg Indeterminacy Principle
• It is impossible to measure the state of a
  quantum bit without altering it.
• Ultrafast Alice (Transceiver) already exists
• Ultrafast Bob (Receiver) we propose to implement
  a novel SSPD counter.

23
Fiber optics versus optical free spacequantum
cryptography channels

• - The best optical fibers have losses 0.2 dB/km
  and introduce uncontrolled polarization changes.
• - Quantum amplifiers/repeaters are questionable.
• Fiber-based QC channels are applicable for
  local networks (below 100 km).
• Global communications and, especially,
  satellite links require optical free-space QC.

24
Ultrafast Alice
25
Ultrafast Bob
26
Comparison of our SSPD performance with the best
commercially available single-photon detectors at
1.3 mm wavelength
Gated regime with 0.1 per gate after-count
probability. Calculated with 10-4 per gate
probability. Data for a high-speed version
standard devices exhibit 1 105 s-1.
27
PICA System with NbN SSPD at Schlumberger ATT
(now NPTest Inc.)
28
IR radiation image of normally working CMOS

• Weak IR pulsed radiation emitted by switching
  CMOS inverter.
• When Vout is switching from 1 to 0, nMOS emits
  photons. When Vout is switching from 0 to 1, pMOS
  emits photons.

29
Single-photon emission from CMOS transistors
0.35-mm linewidth, 3.3-V bias CMOS circuit
running at 100 MHz
Mepsicron II detector
0.13-mm linewidth, 1.3-V bias CMOS circuit
running at 100 MHz
NbN SSPD detector
30
Single-photon emission from bothnMOS and pMOS
transistors
0.13-mm linewidth, 1.3-V bias CMOS circuit
running at 100 MHz
nMOS
pMOS
31
Conclusions

• - NbN single-photon devices are sensitive to
  radiation from UV to mid-IR. In terms of speed
  and sensitivity they outperform any semiconductor
  photon counters.
• Our best devices reach DE 10 at 1.3 mm and
• DE gt 15 at 0.4 mm - 0.8 mm, leading to
  intrinsic QE close to 100 for visible light
  photons.
• NEP is below 210-18 W/Hz1/2.
• SSPD photoresponse time is 150 ps and jitter
  18-35 ps. Measured counting speed is up to 2 GHz.
• - Implemented in IDS PICA system for VLSI
  circuit testing.
• - Devices-of-choice for fast quantum
  communications.