Quantum Metrological Triangle

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Quantum Metrological Triangle

• Centre for Metrology and Accreditation (MIKES)
• TKK Low Temperature Laboratory
• VTT Quantronics group

Antti Manninen MIKES 9.11.2006
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Quantum metrological triangle in short

• Quantum metrology triangle is one of the greatest
  challenges of modern metrology.
• Is Ohms law U RI valid between
• the quantum standards of voltage, resistance, and
  electric current,
• at uncertainty level of about
• 10-7 or better.
• Do the fundamental constants
• e (electron charge) and h
• (Plancks constant) have the
• same value in all three
• phenomena? Do we
• understand physics
• well enough?
• Redefinition of kg 2011?

Quantum Hall effect
Josephson effect
I n1(e2/h)U
U n2(h/2e)f
I n3ef
Single charge pumping
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Quantum standards of electricity

• Voltage and Josephson effect
• Using Josephson effect, the unit of voltage can
  be related to fundamental constants and frequency
  with relative uncertainty of about 10-10 (U
  n(h/2e)f )
• Nobel 1973 (Josephson)
• Resistance and quantum Hall effect
• Using quantum Hall effect, the unit of resistance
  can be related to the fundamental constants with
  relative uncertainty of about 10-9 (RH (h/e2)/i
  )
• Nobel 1985 (von Klitzing) and 1998 (Laughlin,
  Störmer and Tsui)
• Electric current and single charge pumping
• Using single charge pumping, electric current gan
  be related to electron charge and frequency (I
  kef ) but not yet accurately enough nor at high
  enough current levels
• Not yet Nobel prize

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Principle of experiment
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Biggest challenges

• Current pump
• Cooper pair pump (sluice) invented by TKK/LTL and
  VTT
• A.O. Niskanen et al., Phys. Rev. Lett., 2003
• Zero detector
• SQUID or the new Bloch Oscillating Transistor
  (BOT) invented by VTT and realized by TKK/LTL
• J. Delahaye et al., Science, 2003
• Stable cryoresistor
• The final experiment as a whole
• Comparison of three different quantum standards
  at relative uncertainty of 10-7 or lower
• The new MIKES house

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Bloch Oscillating Transistor (BOT)

• Bipolar transistor based on single charge
  effects in a superconductor / normal metal
  nanostructure
• Developed by VTT and TKK/LTL (J. Delahaye, J.
  Hassel, R. Lindell, M. Sillanpää, M. Paalanen, H.
  Seppä, and P. Hakonen, Science 299, 1045 (2003).
• Especially suitable for measurements at 1 MO
  impedance level (e.g. current pump)

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Cooper pair pump (sluice)

• Superconducting charge pump with maximum current
  approaching 1 nA.
• Invented by TKK/LTL and VTT (A.O. Niskanen, J.P.
  Pekola, and H. Seppä, Phys. Rev. Lett. 91, 177003
  (2003))

Mesoscopic island
-N2e
Gate
6 mm
-N2e
Tunnel junctions of SQUID 2
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First pumping experiments (2004)

• Proof-of-principle experiment in 2004 by TKK/LTL
  and VTT (A.O. Niskanen et al., Phys. Rev. B 71,
  012513 (2005))
• On top of the pumped current there is leakage
  current through the closed SQUID, but the
  difference between positive and negative
  pumping directions shows clear step structure
  with current plateaus at ?I N 2ef

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How to decrease leakage current?

• (MIKES-CoE collaboration)

First idea several SQUIDs in series
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How to decrease leakage current?

• (MIKES-CoE collaboration)

First idea several SQUIDs in series
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How to decrease leakage current?

• (MIKES-CoE collaboration)

First idea several SQUIDs in series
Second idea 3-junction SQUIDs In
progress
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How to decrease leakage current?

• (MIKES-CoE collaboration)

First idea several SQUIDs in series
Second idea 3-junction SQUIDs In
progress Third idea something else?
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Results with the newest sluice
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Financiers of the project

• Academy of Finland
• TKK and VTT Centre of Excellence
• MIKES Research project Quantum Metrology
  Triangle
• Technology Industries of Finland Centennial
  Foundation (starting from January 2007)
• Vilho, Yrjö and Kalle Väisälä Foundation
• MIKES, TKK, VTT