.VQV].QJQC .V1` %:J %ICVH `1H:C :JR:`R `1:JQV].QJ :IG`1R$VJ10V`1 7   V = n (h/2e) ν

Sidney Shapiro University of Rochester 1970s ν = 9.3 GHz

STANDARD ELECTROCHEMICAL CELL V = 1.018 volt Barry Taylor Bill Parker University of Pennsylvania ca. 1968

John Clarke Cambridge University ca. 1967 − ΔV/V < 1x10 8 Tom Finnegan Arnold Denenstein

University of Pennsylvania Group

International Conference on Precision Measurement and Fundamental Constants

NBS, Gaithersburg August 1970

Bill Parker Barry Taylor Don Langenberg

First-Generation Josephson Standards (Plenum, 1983) p. 293. Quantum Metrology and Fundamental Physical Constants B. W. Petley, in in Petley, W. B. Pb-Pb Junction Ic = 700 μA ν ≅ 9 GHz n ≅ 250 10-mV Standard 2 Pb-Pb junctions NBS, Gaithersburg ca. 1972

Bruce Field 10-mV Josephson Standard NBS, Gaithersburg 1972 Brian Josephson 1973 Nobel Laureate Aloke Jain Shen Tsai Joe Sauvageau Jim Lukens

Lukens Group Stony Brook University ca. 1983 − ΔV/V < 2x10 16

− ΔV/V < 3x10 19 V =100 mV Don Sullivan Mogens Levinsen NBS, Boulder University of Copenhagen 1985 ca. 1977

ν = 11.88 GHz Ic = 170 μA A/cm μ

1 $V:RR&CCQ7%JH 1QJ V] VIGV` CURRENT CURRENT

VOLTAGE 50 μV/cm ______MICROWAVE – BIASED JUNCTION DRIVEN DAMPED PENDULUM Nb-Pb Junction A/cm μ Ic = 98 μA 20 ν = 20.35 GHz (ω = 1.4) July, 1979 CURRENT CURRENT

VOLTAGE 200 μV/cm

(1H.:`R):% < %`$VJ +1VIV7V` +5Q%CRV` -:`H.  PTB/NBS 1-Volt Array 1984

1,474 Pb-alloy junctions 10x30 mm chip ν = 90 GHz 1-volt Array 1,484 Nb-Pb Junctions 6x13 mm chip NBS, Boulder January 1985 Clark Hamilton NBS, Boulder ca. 1982 ν= 72 GHz

− ΔV/V < 2x10 17 Shin Kosaka Jurgen Niemeyer Akira Shoji

PTB/ETL Collaboration

Dick Harris Frances Lloyd Jim Beall Clark Hamilton Dick Kautz NIST, Boulder May 1989 14,184 Nb-Pb Junctions ν= 87 GHz January 1988 10-volt Array 14,184 Nb-Pb junctions 10x20 mm chip NBS, Boulder January 1988

10-volt Array 20,208 Nb-AlO-Nb Junctions NIST, Boulder, 1992 10x20 mm chip

SECOND-GENERATION JOSEPHSON STANDARDS &00(13-&$$1&4(-+3+1$&4-&(-+ &-1+4+&31+&$&+5&(5$&1(&1(3

-4 10 -5 Weston Cells 10 -6 10 -7 10 -8 Single Junction JVS 10 -9 10 Array JVS -10 10 1930 1950 1970 1990

Year THIRD-GENERATION JOSEPHSON STANDARD Programmable Array 511 externally shunted SIS JJs 75 GHz  :GCV0`Q$`:II:GCV5 :JR:`R7 VI^ _ [ H.1] [ 5 +GR0R&%R+G =%JH 1QJ [  4=<R`10V

Charlie Burroughs 1 cm

[ 3J `1J1H:CC7 :GCV0QC :$V V] [ 0`Q$`:II:GCV``QIU8 QR8 [ jV C1J$ 1IV [ %CC7:% QI: VR [ =1$.JQ1V1II%J1 7:CCQ1R1`VH  HQJJVH 1QJ Hirotaki Yamamori David Olaya Franz Mueller Paul Dresselhaus Sam Benz

PTB/NIST Collaboration Boulder, Colorado, 2008 69,632 Nb-NbSi-Nb Junctions Programmable 10-V Array 300,000 Nb-NbSi-Nb JJs 12x17 mm chip NIST, Boulder 2011 FOURTH-GENERATION JOSEPHSON STANDARD QV].QJ&`G1 `:`7:0V`Q`I7J .V1

• V: %`V – %:J %IRG:VRH:CH%C:GCV :H0QC :$V Q%`HV –  :GCV:H0QC :$V – 0`Q$`:II:GCV:`G1 `:`71:0V`Q`I – QIG1JVRH5:H:JR:`G1 `:`71:0VR`Q`I `%JH 1QJ1J:1J$CV :JR:`R • &]]C1H: 1QJ • -V `QCQ$7 :JR:`R – &51J `1J1H :JR:`R – 0`Q$`:II:GCV.:`IQJ1HQ%`HV » ]VH `%I:J:C71

:IVJ< 0V``VH %:J 1<: 1QJ5VIQJ `: 1QJ

VI1HQJR%H Q`QRV4VJV`: Q`1% ]% • 1JV:0V7J .V1 – 8 @=< QJV – 55G1 HQRVCVJ$ . –  4=<1JV54=<HCQH@ • VI1HQJR%H Q`HQRV $VJV`: Q` – R RH =:`IQJ1HR1 Q` 1QJ QV].QJ%JH 1QJ&``:71% ]% • :HRHQ%]CVR:``:71JV`1V – 5=%JH 1QJ – I`I 0QC :$V – R RH =:`IQJ1HR1 Q` 1QJ 51$1 1

The 7 base units

SECOND MOLE KILOGRAM CANDELA KELVIN METER AMPERE derive from 7 defined fundamental constants

* = Cs hyperfine splitting NA = Avogadro constant h = Planck constant Kcd = Candela constant k = Boltzmann constant c = speed of light e = elementary charge Q.JQJ+Q1V.V`IQIV `7 11 .:%:J 1

• :CH%C:GCV]V%RQRJQ1V1:0V`Q`I VT2 ()=Δ 4 kTRf • &GQC% V VI]V`: %`VH:C1G`: 1QJ

R V(T) T Sense amp amp R' R" V A/D Q QVNS Calibrate A/D

4 K

Correlator Output

-V:%`VRQC

Josephson volt and quantum Hall resistance yield electrical power.

PE = V²/R

Gravitational force and velocity yield mechanical power.

PM = mg/

The Watt balance yields mass. m= V²/Rg/ NIST Watt Balance