High speed photon number resolving detector with titanium transition edge sensors
Daiji Fukuda, Go Fujii, R.M.T. Damayanthi, Akio Yoshizawa, Hidemi Tsuchida, H. Takahashi, S. Inoue, and M. Ohkubo
National Institute of Advanced Industrial Science and Technology(AIST)
Nihon University
The University of Tokyo
The 12th workshop on Low Temperature Detectors, CNAM, Paris, France
C03
23, July, 2007
Outline
• Introduction– Schrödinger's kitten state
• Basic theory for high speed TES
• State of the art of our device– Speed– Energy resolution– Quantum efficiency(QE)
• Summary
Introduction
• There are strong demands to generate, operate, and detect “Single photons” in quantum information fields.– Quantum key distribution (QKD)
– Quantum communication • Quantum teleportation• Quantum optical gate• Quantum decoding
H.Takesue, S.W. Nam and et al.,Nature Photonics 1, (2007) doi:10.1038
Highly secure communication tool
High speed and high capacity communication channels
Schrödinger's kitten state
Requirements for the detectors– Work at an 1550 nm wavelength (0.8 eV)– Energy resolving (Photon number counting)– High speed courting rate ~ MHz.– No dark count– High quantum efficiency ~ 100 % Almost perfect detector..
Ti: Sapphire fs laser
OPASHG
Beam splitter
GatingSchrödinger's kitten state
Photon number resolving detector (PNRD)
Squeezed light pulses
Phys. Rev. A 55, 3184 (1997).
Wigner function2, 4, 6.. 1, 3, 5..
1
Optical TES detectors
• Stanford, NIST, and Albion group– Tungsten based TES (W-TES; Tc~90 mK)
– Energy resolution 0.2 eV• (The energy of a single photon at 1550 nm is 0.8 eV.)
– Quantum efficiency 88 %– Response speed 4 s ( 50 kHz counting rate)
– We need a higher speed TES with a MHz counting rate!
B. Cabrera, R.M. Clarke, C. Colling et al., APL, Vol. 73, 735, 1998
A.J. Miller S.W. Nam, and M. Martinis, APL, Vol. 83, 791-793, 2003
D. Fukuda et al, IEEE trans. Appl. Supercon., Vol. 17, 2007 in printing
1.0
0.9
0.8
0.7
0.6
0.5
Refl
ecti
vity
1. 41.21.00.80.60. 40. 20.0
Photon energy (eV)
Ti W
I r Nb
Au
=1550 nm
R=0. 65
How to improve Speed ?
• The ETF time constant dominated by electron-phonon conduction is described as:
Design of the TES detector
LTAETF
1
1
5 3
The ETF time constant is affected not by the TES volume, but by the operating temperature !
Thus, we have chosen a TITANIUM superconductor for TES, which has Tc at 390 mK in bulk.
R ~ 80 %
R ~ 65 %
•High vacuum EB evaporation on SiN(400nm) film•10 and 20 m device size•46 nm thickness
Optical reflectance Device picture
Si substrateSiN(400nm)
TiNb lead
Optical coupling & Mount Housing
Optical
fiber
TES chip Fiber tip
Signal response to the incident photons at 405 nm wavelength
1.0x10- 6 1.5x10- 6 2.0x10- 6 2.5x10- 6 3.0x10- 6
0.0
1.0x10- 7
2.0x10- 7
3.0x10- 7
4.0x10- 7
5.0x10- 7
n=1
n=2
TE
S c
urr
ent
chan
ge (
A)
time (s)
1 s
rise time 60 nsfall time 300 ns
Averaged pulse
n=3
(exp(- x/ fall
)- exp(- x/ rise
))
Very quick response time !
fall = 300 ns
rise = 60~70 ns
(Thermal diffusion time ~70 ns) Thermal sensitivity ~ 80
Theoretical res. EFWHM= 0.22 eV
Saturation energy Esat= 42 eV
Energy collection efficiency 85 %
Rbias=0.5 Rnormal
0 20 40 60 80 100 120 140
0
50
100
150
200
250
300
350
400
n=4n=3
n=2
counts
/bi
n
channel
n=1
Energy spectrum of the incident photons at 405 nm wavelength
An incident photon number per pulse is dominated by the Poisson distribution.
Thermal healing length ~ 26 m
ENEP is dominated by the excess noise.
Quantum efficiency ~ 5.6 % @ 405 nm
= 405 nm(3.1 eV)
2
)(exp)(
2
1)(
!)(
max
2
2
ln
nl
n
lxlPxN
n
lelP
Incident photon number = 8.6 / pulse
EFWHM=0.76 eV
ENEP
=0.60 eV
Measured, ENEP=0.60 eV
A
d
Rbias=0.5 Rnormal Total noise E=0.25 eV
Phonon noise
Johnson noiseR=2.0
SQ noise=5 pA/Hz1/2
?
M. Ohkubo et al, IEEE trans. Appl. Supercon., 13, 634, (2003).
Energy spectrum of the incident photons at 1550 nm wavelength
0 20 40 60 80 100 120 140 160 1800
20
40
60
80
100
120
140
160
180
200
Counts
/bi
n
Channel
= 1550 nm(0.8 eV) Incident photon number = 25.2 / pulse
EFWHM=0.68 eVn=1
n=2
n=3
n=4
n=5
n=6n=7
ENEP
=0.63 eV
QE~ 9.0 %
Rbias=0.5 Rnormal
Energy spectrum over 100 kHz
10k 100k 1M
0
1
2
3
Energ
y re
solu
tion (
eV
)
Counting rate (Hz)
400 kHz
0 20 40 60 80 100 1200
100
200
300
400
Counts
/bin
Channel
10 kHz 500 kHz 700 kHz10 kHz~400 kHz
500 kHz
700 kHz
Energy resolution vs counting rateEnergy spectrum at high counting rates
No change up to 400 kHz counting rate.
Over 500 kHz, the energy resolution has rapidly degraded.
Sub-MHz counting rate!
= 405 nm(3.1 eV)
Rbias=0.5 Rnormal
Effort to improve QE
800 1000 1200 1400 1600 1800 2000 2200 24000
20
40
60
80
Refl
ecti
vity
(%)
Wavelength (nm)
Landolt- Bornstein New series IV/ 5I
Experimental results
Simulation result
TH30SiO
2(234 nm)/ T i(30 nm)/ SiO
2(287 nm)/ Al(140 nm)/ Si
Optical absorption cavity drastically reduce the reflectance from 65 % to 20 % !
More details, see Poster B05
Optical absorption cavity
D. Rosenberg et al, IEEE trans. Appl. Supercon., 15, 575, (2005).
65 %
20 %
Conclusion
• We have fabricated the Ti-TES operated at 354 mK.
• The response speed of the device is 300 ns.
• Maximum repetition frequency is 0.4 MHz.
• The energy resolution is 0.68-0.76 eV.
• The Quantum efficiency is 5-9%, however, can be improved by optical cavity soon !
Optical coupling & Mount
Housing
Optical
fiber
TES chip Fiber tip
The TES device is coupled to single- mode optical fiber
Highly precise position aligner with 0.1 m
Readout
103 104 105 106 1070.01
0.1
1
10
RTES
= 4.8
f- 3dB
= 5.1 MHz
RTES
= 0
Am
plit
ude
Frequency (Hz)
f- 3dB
= 100 kHz
103 104 105 106 107- 20
020406080
100120140160180
Phas
e (
degr
ee)
Frequency (Hz)
The TES is electrically connected to the SQUID input coil with low inductance < 150 nH = 10 nH (SQUID) + 140 nH (Stray).
Maximum bandwidth of the readout is 5.1 MHz.
The incident photon number can be calculated as,
How to improve Speed ?
• The optical TES is fabricated on the substrate (without SiN membrane structure).
• In this case, Power flows is dominated by a hot-electron effect (n=5).
• The ETF time constant is described as:
Design of the TES detector
LTAETF
1
1
5 3
The ETF time constant is not affected by the TES volume, but the operating temperature !
チタンを使うとか
Response to incident photons at 405 nm
800.0n 1.0μ 1.2μ 1.4μ 1.6μ 1.8μ 2.0μ 2.2μ 2.4μ 2.6μ 2.8μ 3.0μ- 50n
0
50n
100n
150n
200n
250n
300n
350n
400n
450n
500n
n=1
n=2
TE
S c
urr
ent
chan
ge (
A)
time (s)
1 s
rise time 30- 60 nsfall time 300 ns
Averaged pulse
n=3
0 20 40 60 80 100 1200
100
200
300
400
Counts
/bi
n
Channel
10 kHz 500 kHz 600 kHz 700 kHz
Energy spectrum over 100 kHz
10 kHz700 kHz
500 kHz
600 kHz
Response to incident photons at 405 nm
1.0μ 1.5μ 2.0μ 2.5μ- 6.0x10- 3
- 4.0x10- 3
- 2.0x10- 3
0.0
2.0x10- 3
4.0x10- 3
6.0x10- 3
8.0x10- 3
1.0x10- 2
n=3
n=2
Puls
e h
eig
ht
(V)
time (s)
1 s
n=1
rise time 60 nsfall time 300 ns
Ti films by e-beam evaporation
Nb electrodes by DC sputtering
Transition Temp. Tc 359 mK
Heat capacity* C 5.1fJ/K
Thermal conductance G 0.9 nW/K
Intrinsic time constant τ0 5.4 μs
Energy resolution* ∆EFWHM
0.21 eV
Hot electron effect in Ti-TES
• IVとの関連
Read-out & mounting
103 104 105 106 1070.01
0.1
1
10
RTES
= 4.8
f- 3dB
= 5.1 MHz
RTES
= 0
Am
plit
ude
Frequency (Hz)
f- 3dB
= 100 kHz
103 104 105 106 107- 20
020406080
100120140160180
Phas
e (
degr
ee)
Frequency (Hz)
ADRの写真にする?
Optical coupling & Mount
Housing
Optical
fiber
TES chip Fiber tip
Device fabrication• EB evaporation
Ti-TES on SiN films
Film thickness d 45 nm
Transition Temp. Tc 359 mK
Heat capacity * C 2.1 fJ/K
Thermal conductance G 0.9 nW/K
Intrinsic time constant 0 2.3 s
Energy resolution*EFWHM 0.21 eV
1.0
0.9
0.8
0.7
0.6
0.5
Refl
ecti
vity
1. 41.21.00.80.60. 40. 20.0
Photon energy (eV)
Ti W
I r Nb
Au
=1550 nm
R=0. 65