An Electronic Primary Thermometer Based on Thermal Shot Noise Lafe Spietz, K.W. Lehnert, Irfan Siddiqi, R.J. Schoelkopf Department Of Applied Physics, Yale University Thanks to: Michel Devoret and Dan Prober

Introduction Thermal-shot noise in tunnel junctions: a voltage-dependent combination of Johnson noise and shot noise Relates T and V using only e and kB Demonstration of functional form for tunnel junction T=800 mK to >10 K

Fundamental Noise Sources Johnson-Nyquist Noise Frequency-independent Temperature-dependent Used for thermometry Shot Noise Frequency-independent Temperature independent

Conduction in Tunnel Junctions M I M Difference gives current: Assume: Tunneling amplitudes and D.O.S. independent of Energy

Thermal-Shot Noise of a Tunnel Junction* Sum gives noise: *D. Rogovin and D.J. Scalpino, Ann Phys. 86,1 (1974)

Thermal-Shot Noise of a Tunnel Junction 2eI Shot Noise Transition Region eV~kBT 4kBT Johnson Noise R

Tunnel Junction: Dolan Bridge Fabrication Dolan Resist Bridge(SEM) Al-AlOX-Al Junction(AFM)

The Measurement For t = 1 second

Self-Calibration Technique for Thermometry P = GB( SIAmp+SI(V,T) )

Comparison of normalized data to functional form over wide range

Merits Vs. Complications Fast and self-calibrating Primary Wide T range (mK to >10K) No B-dependence Measures electron temperature Possibility to relate T to frequency!* Complications Self heating Frequency dependence* I(V) nonlinearities from: Density of states Barrier shape Weak localization, etc Amplifier nonlinearity *R. J. Schoelkopf et al., Phys Rev. Lett. 80, 2437 (1998)

Summary New Tunnel Junction Thermometer based on voltage and temperature dependent noise of a tunnel junction (thermal-shot noise.) Fast, accurate thermometer works over a wide temperature range Relates T to V using only e and kb implications for metrology