Infrared superconducting
single-photon detectors
Robert Hadfield
Heriot-Watt University, Edinburgh, UK
Chandra Mouli Natarajan, Mike Tanner, John O’Connor Heriot-Watt University, UK
Burm Baek, Marty Stevens, Sae Woo Nam NIST, USA
Shigehito Miki, Zhen Wang, Masahide Sasaki NICT, Japan
Sander Dorenbos, Val Zwiller TU Delft, The Netherlands
Jonathan Habif, Chip Elliot BBN Technologies, USA
Hiroke Takesue NTT, Japan
Qiang Zhang, Yoshihisa Yamamoto Stanford, USA
Alberto Peruzzo, Damien Bonneau, Mirko Lobino, Mark Thompson, Jeremy O’Brien U. Bristol, UK
Infrared superconducting
single-photon detectors
• Introduction to photon counting
• Superconducting nanowire single photon detectors
(SNSPDs): device concept and evolution.
• Applications of SNSPDs in quantum information science:
measurements of quantum emitters, quantum key
distribution, quantum waveguide circuits.
• Outlook: challenges and opportunities for this
technology.
Robert Hadfield – RIT Detector Virtual Workshop 2011
What is a Photon?
• The term ‘Photon’ coined in 1926 following Einstein’s explanation of the photoelectric
effect. Quantum of electromagnetic radiation E=hn.
Robert Hadfield – RIT Detector Virtual Workshop 2011
What is a Photon?
• The term ‘Photon’ coined in 1926 following Einstein’s explanation of the photoelectric
effect. Quantum of electromagnetic radiation E=hn.
• Some prominent detractors:
Willis Lamb ‘Anti-Photon’ Appl. Phys. B 60 77 (1995)
Indian Proverb:
Six wise men went
to see an elephant
(though all of them
were blind)..
Robert Hadfield – RIT Detector Virtual Workshop 2011
What is a Photon?
• The term ‘Photon’ coined in 1926 following Einstein’s explanation of the photoelectric
effect. Quantum of electromagnetic radiation E=hn.
• Some prominent detractors:
Willis Lamb ‘Anti-Photon’ Appl. Phys. B 60 77 (1995)
• The following definition appears to cut the Gordian Knot:
‘A photon is what a photodetector detects’ (Roy Glauber)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Photon-counting detectors
• Human eyes are sensitive down
to the (few) photon level.
• Photomultipliers photocathode +
dynode multiplication
• Semiconductor single-photon
avalanche photodiodes (SPADs)
• Superconductors
numerous detector examples,
including superconducting
nanowires
Robert Hadfield – RIT Detector Virtual Workshop 2011
Photon-counting detectors
• Human eyes are sensitive down
to the (few) photon level.
• Photomultipliers photocathode +
dynode multiplication
• Semiconductor single-photon
avalanche photodiodes (SPADs)
• Superconductors
numerous detector examples,
including superconducting
nanowires
Robert Hadfield – RIT Detector Virtual Workshop 2011
Photon-counting detectors
• Human eyes are sensitive down
to the (few) photon level.
• Photomultipliers photocathode +
dynode multiplication
• Semiconductor single-photon
avalanche photodiodes (SPADs)
• Superconductors
numerous detector examples,
including superconducting
nanowires
Robert Hadfield – RIT Detector Virtual Workshop 2011
Photon-counting detectors
• Human eyes are sensitive down
to the (few) photon level.
• Photomultipliers photocathode +
dynode multiplication
• Semiconductor single-photon
avalanche photodiodes (SPADs)
• Superconductors
numerous detector examples,
including superconducting
nanowires
Robert Hadfield – RIT Detector Virtual Workshop 2011
Single-photon detectors
& applications
Astronomy
Applications
Life Sciences
FLIM/FRET
Quantum
Optics
Free space comms
and LIDAR
IC Testing
Wavelength
Photomultipliers
Detectors
Si SPADs
IR PMTs
InGaAs SPADs
Superconducting detectors
Robert Hadfield – RIT Detector Virtual Workshop 2011
Quantum Atmospheric
cryptography Sensing
in fibre
Characteristics of single-photon detectors
• High quantum detection efficiency at wavelength of interest.
• Probability of noise-triggered ‘dark counts’ low.
• Time between detection of photon and generation of electrical
signal should be constant – low jitter.
• Short recovery time (‘dead time’).
• Ability to resolve photon number.
Review article: Hadfield RH ‘Single-photon detectors for optical quantum
information applications’ Nature Photonics 3 (12) 696 (2009)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Superconducting nanowire single photon
detectors (SSPDs or SNSPDs)
Key Properties:
• Wide spectral range (visible – mid IR)
• Free running (no gating required)
• Low dark counts
• Low timing jitter
• Short recovery time
Considerable scope for
further improvements!
Gol’tsman et al Applied Physics Letters 79 705 (2001)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Superconducting nanowire
single-photon detector
Bias Current
Sapphire
substrate
Incident
Photon
R=0
R>0
Hot spot
(R > 0)
NbN
T~ 4K
→ Voltage Drop = 0
Current density
above
3.5
nm critical
100 nm
Gol’tsman et al., Applied Physics Letters 79, 705 (2001)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Superconducting nanowire
single-photon detector
T~ 4K
Bias Current Reduced
Sapphire
substrate
R>0
Hotspot
Growth
→ Voltage Pulse Out
NbN
V(t)
Gol’tsman et al., Applied Physics Letters 79, 705 (2001)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Superconducting nanowire
single-photon detector
Bias current
Bias Current
suppressed
Sapphire
substrate
NbN
V(t)
Recovery:
• Hotspot shrinks as heat is dissipated into substrate
• Current builds up limited by inductance of nanowire
Robert Hadfield – RIT Detector Virtual Workshop 2011
Evolution of SNSPD design
Single
wire
Meander
Efficient optical coupling is a challenge:
Practical detection efficiency
= coupling efficiency x intrinsic quantum efficiency
=> Increase active area
100
100nm
nmwide
widewire,
wire,
~10 mm~5x mm
10 mm
longarea
Verevkin
Gol’tsman
APLAPL
2002
2001
Robert Hadfield – RIT Detector Virtual Workshop 2011
Evolution of SNSPD design
Next step:
Optical
Meander
Cavity
Practical detection efficiency
= coupling efficiency x intrinsic quantum efficiency
=> Boost absorption to increase intrinsic QE
100 nm wide
nanowire
wire,
~10 mm x 10 mm area
Light
substrate mirror
Verevkin
Rosfjord
APLOX
2002
2006
Robert Hadfield – RIT Detector Virtual Workshop 2011
Evolution of SNSPD design
Single wire
Practical detection
efficiency low
Meander
Increase coupling
Max intrinsic
efficiency ~20% at
1550 nm
Robert Hadfield – RIT Detector Virtual Workshop 2011
Optical Cavity
Increase absorption
Best reported
intrinsic efficiency
57% at 1550 nm
Other developments in SNSPD design
Photon number resolution with spatial multiplexing (SINPHONIA, MIT)
Dichovy et al Nature Photonics 2008
SNSPDs on Si substrates (Delft)
Dorenbos et al APL 2008
Dauler et al J. Modern Optics 2009
Detector embedded in waveguide (MIT, Yale, TUe)
Hu IEEE Trans Appl. Supercon. 2009;
Sprengers arXiv 1108.5107; Pernice arXiv 1108.5299
Robert Hadfield – RIT Detector Virtual Workshop 2011
Superconducting nanowire single-photon
detector system
•High efficiency SNSPDs from TU Delft
Tanner et al Applied Physics Letters 96 221109 (2010)
• 4 or more fiber-coupled SNSPDs can be implemented into a practical, closed-cycle
refrigerator system
Hadfield et al Optics Express 13 (26) 10864 (2005)
SNSPD system at Heriot-Watt
Robert Hadfield – RIT Detector Virtual Workshop 2011
Superconducting nanowire single-photon
detector system: practical performance
Tanner et al Applied Physics Letters 96 221109 (2010)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Quantum information science
with single photons
• Quantum systems can be used to encode and manipulate information.
• QIST promises dramatic improvements in secure communications
metrology, and computation.
• In principle many candidate quantum systems (trapped ions, spins in
semiconductor quantum dots, superconducting circuits..)
• Optical photon makes an ideal ‘flying qubit’
• Photons have low decoherence even at room temperature, easy to route
and manipulate
e.g. polarization
of photon
|0 +|1
Superconducting single-photon photon
detectors for
quantum information science
• Faithful detection of single photons is a key challenge.
Hadfield Nature Photonics 3 (12) 696 (2009)
• Superconducting nanowire single-photon detectors (SSPDs or SNSPDs)
have are an important emerging photon-counting technology.
• SNSPDs have an important role in new QIS applications:
Characterization of quantum emitters
Quantum Key Distribution (QKD)
Operation of quantum waveguide circuits
Robert Hadfield – RIT Detector Virtual Workshop 2011
Characterization of quantum emitters
1 ps, 780 nm
Ti:Sapphire
Laser
Fast Photodiode
Start
BS
82 MHz
Monochromator
@ 935 nm
Dichroic
BS
Sample
InGaAs/GaAs QW, Room Temp
Fiber
Cryostat
5
5
10
Conventional
Si APD
4
10
4
3
10
Fast
Si APD
2
10
Conventional
Si APD
10
Counts
Counts
Stop
SSPD
10
1
Fast
Si APD
3
10
2
10
SSPD
1
10
SSPD
0
10
-500
TAC/MCA
Timing Electronics
0
Instrument
Responses
500
Time (ps)
1000
1500
10
Decays
0
10
-500
0
500
Time (ps)
Stevens et al Applied Physics Letters 89 031109 (2006)
1000
1500
Quantum dot single-photon sources for
quantum information science applications
•Self-assembled quantum dots in III-V semiconductor are a promising source of single
photons for optical QIS.
Michler et al Nature 290 2282 (2001)
•Single photon emission is verified by g(2)(0) measurement.
•These measurements were on emitters at l ~900 nm; SNSPDs would also enable
measurements on telecom wavelength single-photon sources
Hadfield et al Optics Express 13 10846 (2005)
Hadfield et al Journal of Applied Physics 101 103104 (2007)
Long wavelength characterization of
quantum emitters using SNSPDs
•Si single photon avalanche photodiodes do not work at l>1 mm.
•SNSPDs can be used for characterization of long wavelength emitters.
3
Counts
10
InGaAs grown on InP
lDetect = 1650 nm
Fit:  = 290 ps
2
10
Stevens et al Applied Physics
Letters 89 031109 (2006)
1
10
IRF
Decay
Data
0
10
-500
0
500
1000
1500
2000
2500
Time (ps)
• These measurements were carried out on semiconductor single-photon emitters; this
technique would be equally applicable to studies of single photon emission from diamond
defect centers, FLIM and FRET for single molecules and singlet oxygen detection.
Robert Hadfield – RIT Detector Virtual Workshop 2011
Quantum Key Distribution
(Bennett & Brassard, 1984)
hn
Alice
Bob
Eve
R. Liechtenstein
•Quantum Key Distribution is a method for two parties (‘Alice’ and ‘Bob’) to create a
‘key’ for encrypting subsequent messages.
•Information encoded on single photons via phase or polarization
•Any attempted eavesdropping introduces errors and is therefore detectable.
Robert Hadfield – RIT Detector Virtual Workshop 2011
Quantum Key Distribution – range limitations
• Above a certain error rate (QBER) threshold, secure key can no longer be
generated.
• There are two contributions to the error rate (QBER):
QBER total = QBER interferometer + QBER dark counts
Fixed ~1%
Dark count rate / Sifted bit rate
11 %
Log(Key Rate)
QBER
• As the transmission distance increases, the number of detected bits falls, so the
error rate rises, causing the secret bit rate to eventually fall to zero.
Robert Hadfield - Heriot-Watt Quantum
DistancePhotonics Workshop
Sifted
Secret
Distance
Superconducting nanowire single-photon detectors
in Quantum Key Distribution
Superconducting nanowire single-photon detectors: benefits for
QKD in optical fibre:
- Single-photon sensitivity at 1550 nm
- Low dark counts
- Low timing jitter
- Gaussian instrument response function
Robert Hadfield – RIT Detector Virtual Workshop 2011
=>Long distances
=>High bit rates
First QKD demonstration with SNSPDs
in the DARPA quantum network
• A collaboration between NIST and BBN Technologies (Jonathan Habif, Chip Elliot)
sponsored by the DARPA QuIST programme.
• First prototype SNSPD system delivered to BBN end 2005.
Clock rate 3.3 MHz
Bob
42.5 km spool
Bit rate (bits/s)
Alice
(behind)
25 km spool
Link loss (dB)
SNSPD Closed-cycle system
Hadfield et al Applied Physics Letters 89 241199 (2006)
World record result for long distance
QKD in optical fiber using SNSPDs
•
•
Demonstration carried out end 2006 in Yamamoto lab, Stanford University
(Stanford/NTT/NIST)
10 GHz clocked QKD system at l= 1550 nm using superconducting detectors
10 GHz
1 GHz
Takesue et al Nature Photonics 1 343 (2007)
Robert Hadfield – RIT Detector Virtual Workshop 2011
New directions in QKD: ground to space
Vision of European Space Agency SpaceQUEST topical team
(led by Prof. Anton Zeilinger, University of Vienna):
QKD from the International Space Station (ISS).
Role for SNSPDs?
Photon flux
Microlens
array
Cavity enhanced nanowire pixels
R Ursin et al Europhysics News 40 (3) 26 2009
Robert Hadfield – RIT Detector Virtual Workshop 2011
Quantum waveguide circuits
Jeremy O’Brien, University of Bristol
Optical waveguide circuits can be used to replace conventional optics.
Politi et al Science 320 5876 (2008)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Operating quantum waveguide circuits
with SNSPDs
with Jeremy O’Brien, University of Bristol, UK
SNSPDs
SMF
BiBO
μm actuator
Waveguide
Circuit c
a
d
b
CW laser,
402nm,
60mW
804nm photon
pairs
Filter
PMF
Robert Hadfield – RIT Detector Virtual Workshop 2011
TCSPC
Card
Operating quantum waveguide circuits with
SNSPDs: initial experiments at l=805 nm
• First generation quantum waveguide circuits: silica on silicon waveguides, downconversion
pair source at l=850 nm (as used in Politi et al Science 320 5876 (2008))
•SNSPDs replace Si SPADs
•Demonstrations:
-Two photon interference (Hong-Ou-Mandel dip)
-Tuned two phonon interference with resistive phase shift
-CNOT gate
F=90.4%
VSNSPD 92.3 %
Natarajan et al Applied Physics Letters 96 211101 (2010)
Robert Hadfield – RIT Detector Virtual Workshop 2011
Operating quantum waveguide circuits with
SNSPDs: migrating to telecom wavelengths
• First generation quantum waveguide circuits: silica on silicon
waveguides, downconversion pair source at l=850 nm and Si SPAD
detectors
Politi et al Science 320 5876 (2008)
• A much wider range of high performance waveguide components
(compact low loss waveguides, high speed switches and modulators)
• SNSPDs allow operation of next generation quantum waveguide
circuits at 1550 nm.
• Recent reports show that SNSPDs can also be integrated on-chip with
the waveguide. This is crucial for the scalabilty of circuits in demanding
applications such as optical quantum computing.
Robert Hadfield – RIT Detector Virtual Workshop 2011
Heralded source with fast lithium niobate switch
 V
Switching efficiency
97 . 9  0 . 1 %
MZI driven with a 4 ns rising time pulse
Bonneau et al Fast path and polarization manipulation of telecom wavelength single
photons in lithium niobate waveguide devices arXiv 1107.3476 (2011)
Fast switching of quantum interference
Signal generator
C1 C2
a
SPDC
b
  
11  sin 
  20  02
 2
c
 =p/2
=0
d
  cos   11
Counting logic
C2
Counting logic with toggle between two separate
counters
Square waves 4MHz
2  2%
C1
82  2 %
Bonneau et al Fast path and polarization manipulation of telecom wavelength single
photons in lithium niobate waveguide devices arXiv 1107.3476 (2011)
Infrared superconducting single-photon detectors
Outlook
Superconducting nanowire single-photon detectors (SNSPDs) offer very good
practical performance at telecom wavelengths and have successfully been used
in challenging quantum information science experiments.
Prospects and challenges for SNSPD development:
• Achieving high efficiency at mid IR wavelengths
• Reducing the timing jitter
• Increasing the active area
• Integrating devices on-chip with optical and electrical elements (optical
waveguide circuits, readout electronics)
Potential breakthroughs:
• Large area single photon detectors/detector arrays with high efficiency,
picosecond timing resolution and gigahertz count rates from UV to mid IR
wavelengths
• Adoption in new application areas: quantum communications and
computing, LiDAR, astronomy, life sciences, integrated circuit testing
Robert Hadfield – RIT Detector Virtual Workshop 2011