the shot noise thermometer lafe spietz, k.w. lehnert, i. siddiqi, r.j. schoelkopf department of...
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The Shot Noise Thermometer
Lafe Spietz, K.W. Lehnert,
I. Siddiqi, R.J. Schoelkopf
Department of Applied Physics, Yale University
Thanks to:
Michel Devoret, Daniel E. Prober, and Wes Tew
Introduction
• Johnson-Schottky transition of the noise in tunnel junctions
• Relates T and V using only e and kB
primary thermometer
• Demonstrate operation fromT=0.02 K to 300 K*
*Lafe Spietz et al, Science 300, 1929 (2003)
Thermometry
Secondary: Needs to be calibrated from some outside standard, e.g. resistive thermometers
Primary: Needs no outside calibration—based on understood physics, e.g. ideal gas thermometer
Desirable Characteristics for a Thermometer:
• Wide Range• Fast• Primary• Accurate• Easy and simple to use• Physically compact
ResistanceThermometers
Cryogenic Thermometry: Overview
1 K
300 K
10 K
0.1 K
0.01 K
100 K
RuOx 50 mK
3He Melting CurveCBT
JohnsonNoise
Nuclear Orientation
Fundamental Noise SourcesJohnson-Nyquist Noise
• Frequency-independent• Temperature-dependent• Used for thermometry
• Frequency-independent • Temperature independent
( ) 2IS f eI
4( ) B
I
k TS f
R
2A
Hz
2A
Hz
Shot Noise
Conduction in Tunnel Junctions
Assume: Tunneling amplitudes and D.O.S. independent of energy
Fermi distribution of electrons
V
I
(1 )
(1 )
L R L R
R L R L
GI f f dE
eG
I f f dEe
L R R LI I I GV Difference gives current:
Conductance (G) is constant
Fermi functions
Thermal-Shot Noise of a Tunnel Junction*
( ) 2 coth2I
B
eVS f eI
k T
Sum gives noise:
( ) 2 ( )I L R R LS f e I I
*D. Rogovin and D.J. Scalpino, Ann Phys. 86,1 (1974)
I GV
Thermal-Shot Noise of a Tunnel Junction
( ) 2 coth2I
B
eVS f eI
k T
Johnson Noise
2eIShot Noise
4kBTR
Transition Region eV~kBT
off off
B B
e(V - V ) e(V - V )Fit = Gain Coth - T
2k 2k T
High Precision Measurement
2 1.04
Re
sid
ual
s
502.5 .094T mK mK 51.0001 6.7 10Gain
18 4.2Offset nV nV
Modular SNT Package
Total cost of package <10$
Tunnel Junction
Built-in Bias Tee(on-board SMTComponents)
Copper Plumbing parts
SMA Connectors for RF
Copper Tubing for DC lines
Future Work• Determine effect of nonlinearity on shot noise• Measure heating effects with dirty film• Improve room temperature results• Measure hydrogen triple point• Make SNT more modular and easy to use for
use in other labs and for commercialization• Push the lower temperature end with lower
system noise temperature and more careful filtering
Summary
• Demonstrate functional form of junction noise0.02 - 300 Kelvin*
• Use as fast, accurate thermometer
• As good as 200 ppm precision, 0.1% accuracy
• Relates T to V using only e and kB Possible kB determination?
*Lafe Spietz et al, Science 300, 1929 (2003)
Null-Balancing Noise Measurement for High Precision
Noise Contours in Voltage-Space
Small range of noise keepsdetector in linear range
Temperature Measurements Over Time
6.0
5.5
5.0
4.5
4.0
T a
nd
Tno
ise(
K)
1086420Time [hours]
75.0
74.5
74.0
73.5
73.0
Ga
in [1
0-6V
/K]
Tfit
TRhFe
Tnoise
Gain
Experimental Setup:RF + DCMeasurement and Thermometry
capacitors
inductors
RhFe Thermometer
RuOx Thermometer
device
B B
eV eVFit = Gain Coth -T
2k 2k T
2 1.49
Fit With Two ParametersR
esi
du
als
502.5 .094T mK mK 51.0001 6.7 10Gain
Merits Vs. Systematics
*R. J. Schoelkopf et al., Phys Rev. Lett. 80, 2437 (1998)
• Possibility to relate T to frequency!*
• Compact electronic sensor
• No B-dependence
• Wide T range
(mK to room temperature)
• Fast and self-calibrating• Primary
Merits Systematics
• I-V curve nonlinearities
• Amplifier and diode nonlinearities
• Frequency dependence*
• Self-heating
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