Quantum Metrology Closing the Quantum Triangle

Transcription

1 Quantum Metrology Closing the Quantum Triangle Quantum Triangle Heikki Seppä VTT Information Technology

2 From Quantum Metrology into the Practical Applications MEG Printable Electronics Quantum Metrology Biosensors < 10 K > 250 K Micro-Devices Nanobased Devices

3 Quantum Devices and Low Temperature Phenomena VTT s role in Centre of Excellence

4 OUTLINE Quantum Triangle can we close it within 10-7 Quantum Hall no problem, but the resistance is Josephson Voltage Standard no problem Quantum Current Standard too low current, but our Sluice? Null Detector current sensitivity not enough, but our BOT? Some Josephson Junction Based Devices invented at VTT Un SQUID, Double Junction SQUID, low noise, high gain idea 1992, patented 1994, first experiment 1994, commercial 2005? FDJJA, Programable Josephson Voltage Array, idea 1998, experiments , about 100 components BOT, Bloch Oscillating Transistor Mesoscopic Current Amplifier idea 2000, experiement , about 3 4 working samples Sluice, Cooper Pair Pump, idea 2003, experiments , 1 bad and 1 good component BOM: Bloch Oscillating Magnetometer, not yet realized SETBOT: BOT based Electrometer, not yet realized

5 OUTLINE How to realize the quantum triangle our proposal Josephson devices our approach un SQUID Josephson programmable voltage standard our approach Bloch Oscillating Transistor Cooper pair pump Uncertainty of the quantum triangle Remaining problems to realize the quantum triangle

6 Quantum Triangle I=m2ef p I n(e 2 /h) 10 MΩ resisance R tracable to the quantum Hall??? V=n(h/2e)f J Josephson voltage standard Sluice current pump BOT null detector Control f J VTT/TKK Mikes VTT/TKK SQUID post amplifier VTT VTT/Mikes 50 mk 4.2 K

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9 a) 1. r 02 =1 ϕ a =π/ ϕ a =π/ ϕ a =0 b) r =0.5 ϕ =π/2 ϕ a =π/4 ϕ a =0 c) r = C urent Cu rent Cur rent ϕ a =π/4 =π/2 ϕ =0 Bia svo ltag e a VTT TECHNICAL RESEARCH CENTRE OF FINLAND Double Junction SQUID based on unshunted Josephson Junctions L/2 L/2 I DC SQUID R C I c I c C R Undamped Josephson Junction R ac C ac C I c L/2 L/2 L R dc dc I c L b C I b R ac C ac U b Un SQUID Hg SQUID Modified un SQUID Modified Hg SQUID High-Gain SQUID

10 IV Characteristics of the un and hg SQUIDs hg SQUID un SQUID Current point of operation 0.2 voltage bias Voltage Current Voltage

11 Integrated SQUID magnetometer

12 Programamble Josephson Voltage Standard To make a fast array Josephson junctions have to be damped. Usually SNS or SINIS junctions are used (NIST and PTB). Unfortunatelly, the microwave pump will be strongly damped. If the pump frequency exceeds the plasma frequency we can manipulate damping in such a way that there is damping for the plasma resonance and for the signal frequencies but not for the pump signal. Our idea is to use SIS junctions with a LR circuit across them. It turns out that the speed of the array depends on current step width, microwave power and the output voltage in a complicated way. We have optimized very fast devices for 1.5 V output signals to generate accurate ac signals and 10 V arrays used as a programable dc voltage source. Z 1 Z 2 Z 3 Z 1 Z g I j ~ V Z C g 0 Z 0 Z L

13 1 V Array Based on FD Josephson Junctions 2 microawe brances 4 th step 1400 junctions Ic = 1 ma 1 khz sinusoidal signal, uncertainty less than 0.01 ppm Voltage (V) µv µa 2.10 Current (ma) 2.15

14 10 V Array 32 microwave brances junctions 3 th step Ic = 450 ua 70 GHz V out1 V out2

15 IV Characteristics of 1 V Array Voltage (V) Hajontainen laskettu Current (µa)

16 IV Characteristics of 10 V Array 12 Suffering from resonance at 140 GHz, pump 70 GHz 10 Voltage (V) Current (ma)

17 Bloch Oscillating Transistor - BOT C 1,R T1 C R I C I B +Q1 -Q1 +Q2 B V CC V B C 2,I cs E -Q 2 BOT can be considered as a complementary component of the SET in the same fashion as the BJT (Bipolar Junction Transistor) is complementary to the FET (Field Effect Transistor)

18 Operation Principle I C I C 4 Energy Diagram R +Q 2 +Q 2 -Q 2 -Q 2 Energy (e 2 /2C 2 ) Coherent Cooper pair tunneling Singleelectron tunneling Zener tunneling Quasicharge (e)

19 Experiments Collector current I C S-N tunnel junction Bias current I B S-S tunnel junctions (squid) S-N junction Cu Al Al S-S junctions (squid) Cr resistanc e Emitter voltage V E