Transcript Snímek 1

Detectors of single photons
(…on the road to nano)
O. Haderka
Regional Center for Advanced Technologies and Materials, Joint
Laboratory of Optics, Palacký University, 17. listopadu 50a,
772 07 Olomouc, Czech Republic.
Why to detect single photons?
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In classical optics – every photon is
valuable (e.g., in astronomy)
In quantum optics/information
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time-correlated photon counting (TCPC)
some tasks benefit from single photons (QKD,
QM)
other tasks require single photons (LOQC)
Other applications in particle physics,
biomedical research, atmospheric
pollution measurements, LIDAR etc.
Photon detection event
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Coupling
Conversion of optical quanta to another medium
(usually electron or electron-hole pair)
Amplification to macroscopic level
Sampling/Thresholding
coupling
optics
internal
coupling
detector
amplifier/
integrator
gain
losses
ηentry
n
sampling/ADC
ηconv ηcollect γint
m
γext
x
General characteristics
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Spectral properties
 conversion quantum
efficiency ηconv
Timing properties
 dead time
 jitter
Noise properties
 dark count rate d
 probability of afterpulses
Ability to resolve number of
photons
 excess noise
 pulse-height diagram
 single-shot vs. statistics
80
photomultiplier
hybrid photodetector
Si SPAD
InGaAs SPAD
70
60
Quantum efficiency [%]
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50
40
30
20
10
0
200
400
600
800
1000
1200
Wavelength [nm]
1400
1600
1800
Overview of current technologies
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Photomultiplier tubes
Avalanche photodiodes
Hybrid photodetectors
Visible light photon counters
Transition-edge sensors
Frequency up-conversion
Superconducting nanowires
Quantum dots & defects
Carbon nanotubes (?)
Hamamatsu
Burle
Photomultiplier tubes
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the oldest photon-counting
detector (1949)
large active areas
( > 10 mm)
amplification excess noise can
be lowered using first dynode
from suitable material (GaP)
η = 40% @ 500 nm (GaAsP)
d ≈ 100 Hz, Δt ≈ 300 ps
η = 2% @ 1550 nm
(InP/InGaAs @ 200 K),
d ≈ 200 kHz
Single-photon avalanche
photodiode (SPAD)
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Perkin-Elmer
Micro Photon Devices
idQuantique
photodiode reverse biased
above breakdown
(Geiger mode)
avalanche stopped by
quenching circuit
Si: η = 70% @ 650 nm, d ≈ 25 Hz,
Δt ≈ 400 ps, τ = 50 ns, high excess noise
back-flashing
d can be lowered to 8x10-4 Hz by cooling to 78K
shallow-junction: Δt ≈ 40 ps
InGaAs/InP: η = 20% @ 1550 nm, d ≈ 10 kHz,
Δt ≈ 400 ps, τ = 10 μs, high excess noise,
gating necessary
Hamamatsu
Hybrid photodetectors
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combination of a
photocathode with
avalanche
photodiode
low excess noise
due to single largeamplification step
η = 46% @ 500 nm,
d ≈ 1 kHz,
Δt ≈ 35 ps
Albota et al., OL 29, 1449 (2004)
Langrock et al., OL 30, 1725 (2005)
Frequency up-conversion
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conversion
1550 nm
of IR-photons
630 nm
to a region with 1064 nm
better detectors
PPLN: 90% conversion
very intense pumping needed (cavity or
waveguide)
high-noise (background nonlinear processes
emitting at target wavelength due to strong
pumping)
η = 46% @ 1550 nm, d ≈ 800 kHz,
Δt ≈ 400 ps (thick junction Si SPAD)
coherent up-conversion is feasible
Kim et al., APL 74, 902 (1999)
Takeuchi et al., APL 74, 1063 (1999)
Visible-light photon counters (VLPC)
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controlled single-carrier
multiplication process
@ 6K temperature
avalanche triggered by a
hole in As-doped region
confined to  20 μm
resolves up to 5 photons
ηconv = 88% @ 694 nm
(ηconv = 93% @ near IR),
d ≈ 20 kHz, Δt ≈ 250 ps,
τ = 100 ns
Figure by Y. Yamamoto
Cabrera et al., APL 73, 735 (1998)
Rosenberg et al., PRA 71, 061803 (2005)
Lita et al., OE 16, 3032 (2008)
Transition-edge sensors
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superconduction film (W) kept at the
temperature of superconducting transition
(100 mK)
photon-absorbtion induced temperature
change is detected as a current change
resolves up to 8 photons
η = 95% @ 1550 nm,
d ≈ 3 Hz, Δt ≈ 100 ns,
τ = 2 μs
can be done at any
wavelength between
200-1800 nm
Goltsman et al., APL 79, 705 (2001)
Marsili et al., NJP 11, 045022 (2009)
Superconducting nanowires
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100 nm wide nanowire in a thin superconducting
film
NbN @ 1.5-4K (below superconducting transition)
wire biased just below critical current
photon detections create resistive hotspots and
trigger voltage pulses
η = 1-57% @ 1550 nm,
d ≈ 10 Hz, Δt ≈ 30-60 ps,
τ = 10 ns (large area)
deposition of structures
for spatial multiplexing
possible
improvements likely
Rowe et al., APL 89, 253505 (2006)
Kardynal et al., APL 90, 181114 (2007)
Blakesley et al., PRL 94, 067401 (2005)
Quantum dots or defects
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trapping of charge in defects
heterostructures based on III-V compounds
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trapped charge alters conductance in a fieldeffect transistor (ηconv = 68% @ 805 nm,
resolves up to 3 photons)
alters tunneling probability
in a resonant tunnel diode
(ηconv = 12% @ 550 nm,
d = 2x10-3 Hz)
4K temperature needed
improvements likely
Ambrosio et al., NIMPRA 617, 378 (2010)
Carbon nanotubes (?)
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multi-wall carbon
nanotubes are grown
(CVD) on p-doped silicon
substrate
structure behaves like a
photodiode with η≈50%
Multichannel detectors
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[VLPC, HD, nanowires]
Fiber-loops
Solid state photomultipliers
i-CCD cameras
EM-CCD cameras
Haderka et al., EPJD 28, 149 (2004)
Fitch et al., PRA 68, 043814 (2003)
Fiber loops
30 m (150 ns)
delay loop
15 m (75 ns)
delay loop
input
state
APD
10m delay loop
connector
50/50
splitter
50/50
splitter
variable ratio
coupler
input state
connector
50/50
splitter
30 ns electronics
delay
APD
0
10
-1
10
-1
-2
10
10
-2
Probability
Probability of detection
10
10-3
10
-3
10
-4
10
-4
10-5
-5
10
200
400
600
800
1000
Time Delay after start pulse [ns]
1200
0
200
400
600
800
Delay after trigger [ns]
1000
1200
Hamamatsu
Multi-pixel photon counter
(silicon photomultiplier)
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array of APDs in
Geiger mode
currently
100 – 1600 pixels
crosstalk due to
back-flashes
η = 65% @ 440 nm,
d = 6 x 105 Hz,
Δt ≈ 200-300 ps
Andor
Roper Scientific
Hamamatsu
iCCD cameras
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η = 25% @ 550 nm,
d ~ 104 Hz,
Δt ≈ 2 ns
Andor
Roper Scientific
Hamamatsu
EM-CCD (L3) cameras
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high η of backilluminated CCDs
single photon sensitivity
CIC noise
‘slow’ shutter
η = 97% @ 550 nm
Figures of merit
For binary detectors:
efficiency factor Qeff
Qeff 

d t
For photon-number resolving detectors:
peak-to-valley contrast
number of resolvable peaks
effective number of channels
n-photon fidelity
ENC  N 1  d t 
2
An
do
r iX
on
+8
4
88
6
400
600
800
1000
Wavelength [nm]
1200
Ha
ma
ma
ts u
H1
1400
03
A-
1600
75
20
01
l. (
d2
ta
ei
ee
qu
su
nti
ke
30
Ta
ua
photomultiplier
SPAD
hybrid photodetector
up-conversion
VLPC
TES
nanowire
quantum dot
fiberloop
iCCD
EMCCD
MPPC
id Q
MP
CC
HP
D
88
An
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MP o r i S
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50
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log(Qeff)
)
( 20
06
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06
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Detector comparison chart [Qeff]
Detector comparison chart [ENC]
100
photomultiplier
SPAD
hybrid photodetector
up-conversion
VLPC
TES
nanowire
quantum dot
fiberloop
iCCD
EMCCD
MPPC
TES
VLPC
80
Si SPAD PE
QD
QE [%]
60
MPPC VIS
nanowire
fiberloop
PD
M
D
A
P
Si S
fiberloop
HPD
PMT VIS
40
EMCCD
MPPC IR
InGaAs SPAD
50
PMT Burle 88
20
iCCD VIS
up-conversion
iCCD IR
PMT IR
0
0
1
2
3
log(ENC)
4
5
6
n-photon fidelity
0
Fidelity Fn
10
photomultiplier
hybrid detector
VLPC
TES
quantum dot
fiber loop
iCCD
MPCC
EM-CCD
-1
10
-2
10
0
2
4
6
8
10
12
14
Input photon number n
16
18
20
Olomouc: Application of single-photon
detectors to twin photon beams
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Characterization of photon-number
correlations
Spatial correlations
Absolute quantum efficiency
measurement
Noise reduction techniques
Type-I spontaneous parametric
down-conversion
τ
Φs Λs
L
θs
θs0
w
Λp
θi0
Φi θi
Λi
Generation and measurement of
photon twins
Detection with iCCD camera
signal
strip
idler strip
noise
reference
summed image
Haderka et al., PRA 71, 033815 (2005)
Photon-number correlations
25 0 %
0%
10
0%
0%
5
0
0
5
10
15
nS
20
25
50
60
70
80
90
n
I
50
60
70
80
90
100
110
120
120
100
110
S
nI
15
15 %
12 %
9%
6%
3%
0%
-3 %
-6 %
-9 %
-12 %
-15 %
n
20
Spatial correlations
40
I
S
30
20
area of
correlation
I [mrad]
10
0
-10
-20
-30
S
I
ideal
phasematching
-40
-40 -30 -20 -10 0 10 20 30 40
S [mrad]
Spatial correlations:
varying the pump beam spectrum
Spatial spectrum of the pump
beam
Temporal pump-field spectrum
Experimental radial cross-section
of the correlation area
Experimental angular crosssection of the correlation area
Spatial correlations:
varying the pump beam shape
CONCLUSION
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Single photon detection technology
makes big leaps
Promising nanotechnologies appear
Both intrinsic and multichannel photonnumber resolution improves
This all should contribute to present &
future quantum information systems