CHAIR OF MESOSCOPIC PHYSICS

Michel Devoret

"FROM ATOMS TO QUANTUM MACHINES"

Inaugural LectureMay 31, 2007

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"SEEING" ATOMS

Jean Perrin Albert Einstein Paul Langevin

Measurement and analysis ofbrownian motion (1908)

YESTERDAY....

.... AND TODAY

Iron atomsarranged on a copper surface(Eigler et al.)

5µm

Surface Review and Letters 2 (1), 127-137 (1995) 07-0-2

ATOM

ELECTRONS NUCLEUS

PROTONS, NEUTRONS

QUARKS

STRINGS?

THE ATOM IS ITSELFA WORLD OF PARTICLES

GRAVITONS?

10-10m

10-15m

10-35m

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YET,ATOMS ARE

NOTMINIATURE

SOLAR SYSTEMS

IN QUANTUM MECHANICS, BASIC NOTIONS LIKETRAJECTORIES AND EVENTSLOSE THEIR USUAL MEANING

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Classical Mechanics

100 102 104 106 108 1010 1012

QuantumMechanics

MACROSCOPIC WORLDmicro-scopicworld

numbersof atoms

100 102 104 106 108 1010 quantas perdegrees offreedom

TWO WORLDS

(complexity)

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SEPARATING THE BORDERLANDS

ClassicalMechanics

100 102 104 106 108 1010 1012

Quantum Mechanics

10-4 10-2 100 102

MESOSCOPIC DOMAIN

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MACROSCOPIC WORLDmicro-scopicworld

numbersof atoms

quantas perdegrees offreedom

(complexity)

WHY EXPLOREMESOSCOPIC SYSTEMS?

ADVANTAGES OFMACRO SYSTEMS:

MODULARITY,FLEXIBILITY,

ACCESSIBILITY

ADVANTAGES OFQUANTUM SYSTEMS:

ORDER,DISCRETENESS,ENTANGLEMENT

QUANTUMLEGO SET

QUANTUMMACHINES?

MESOSCOPIC SYSTEMS:- PARTIALLY CONFINED QUASIPARTICULES- ARTIFICIAL ATOMS

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• WHAT ARE THESE QUANTAS DEFINING THE CLASSICAL-QUANTUMBORDERLAND?

• APPLICATIONS TO METROLOGY AND QUANTUM INFORMATIONPROCESSING : METROLOGICAL TRIANGLE AND SUPER-CONDUCTING QUANTUM CIRCUITS

• CHALLENGES OF MESOSCOPIC SYSTEMS: HOW DO WE MAKE, MEASURE AND CALCULATE THEM?THE QUANTUM POINT CONTACT

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• WHAT ARE THESE QUANTAS DEFINING THE CLASSICAL-QUANTUMBORDERLAND?

• APPLICATIONS TO METROLOGY AND QUANTUM INFORMATIONPROCESSING : METROLOGICAL TRIANGLE AND SUPER-CONDUCTING QUANTUM CIRCUITS

• CHALLENGES OF MESOSCOPIC SYSTEMS: HOW DO WE MAKE, MEASURE AND CALCULATE THEM?THE QUANTUM POINT CONTACT

cosα sinα

we measure:i) angular position αii) angular velocity dα/dt

example:

A COMPLEX SYSTEM WITH THE SIMPLESTDEGREE OF FREEDOM

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ANGLE

ANGULARMOMENTUM

QUANTUM LAWS RESTRICTINFORMATION ACQUISITION

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ANGLE

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ANGULARMOMENTUM

QUANTUM LAWS RESTRICTINFORMATION ACQUISITION

ANGLE

AREA ≥ h

PLANCK'S CONSTANT SETSTHE ACTION QUANTUM....

h ≈ 10-34 J•s Measurement of angular position of hard drive with 16 bits→ velocity fuzz: thousandth of a turn per billion years!

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ANGULARMOMENTUM

TIME

ENERGY AREA ≥ h

ENERGY→TEMPERATURE: 10mK ¥ 1nsh ≈ 10-34 J•s

... THE TRUE INDIVISIBLE QUANTITYOF NATURE

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ANGLE

AREA ≥ h

DISCRETENESS OF CYCLIC SYSTEM

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ANGULARMOMENTUM

ANGLE

INTERFERENCE!

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ANGULARMOMENTUM

DISCRETENESS OF CYCLIC SYSTEM

ENERGY QUANTIZATION

ENERGY OF INCIDENT PARTICLE

SYSTEMENERGY

QUANTUM LIMIT

CLASSICAL LIMIT

∆E=hf

00

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• WHAT ARE THESE QUANTAS DEFINING THE CLASSICAL-QUANTUMBORDERLAND?

• APPLICATIONS TO METROLOGY AND QUANTUM INFORMATIONPROCESSING : METROLOGICAL TRIANGLE AND SUPER-CONDUCTING QUANTUM CIRCUITS

• CHALLENGES OF MESOSCOPIC SYSTEMS: HOW DO WE MAKE, MEASURE AND CALCULATE THEM?THE QUANTUM POINT CONTACT

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THE QUANTUM POINT CONTACT

GaAs

AlGaAs

two-dimensionalelectron gas

WEAKMASS

SPEED

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GaAs

AlGaAs

~ 100 nm

NANOMETRICDIMENSIONSmetallic

electrodes

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THE QUANTUM POINT CONTACT

- -

- -

consider chargehaving traversedcontact in time T

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THE QUANTUM POINT CONTACT

d

ELECTRONIC MODES

FB

hvk Td

LOWTEMPERATURES

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d'

WAVEGUIDE ANALOG

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ELECTRONIC MODES

OF MHOS AND ELECTRONS

22 2

ET eVTNh h

I eN eGV TV h

= =

= = =

number of packets:

conductance: 2

26 kΩ≈

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Energy

Time 0 T

∆E = eV

2

hGe

2

4

8

6

12

10

0

Ug

d

CONDUCTANCE QUANTIZATION

ACCESS TO A QUANTUM PHENOMENONWITH A SIMPLE VOLTMETER!

van Wees et al.1988

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• WHAT ARE THESE QUANTAS DEFINING THE CLASSICAL-QUANTUMBORDERLAND?

• APPLICATIONS TO METROLOGY AND QUANTUM INFORMATIONPROCESSING : METROLOGICAL TRIANGLE AND SUPER-CONDUCTING QUANTUM CIRCUITS

• CHALLENGES OF MESOSCOPIC SYSTEMS: HOW DO WE MAKE, MEASURE AND CALCULATE THEM?THE QUANTUM POINT CONTACT

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IV

Josephsoneffect

quantumHall effect

2hV n fe

= I mef=

2eI p Vh

=

FLUXQUANTIZATION

f

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CHARGEQUANTIZATIONsingle electron

pump

CONDUCTANCEQUANTIZATION

TRIANGLE OF METROLOGICAL MESOSCOPIC EFFECTS

IV

Josephsoneffect

quantumHall effect

2hV n fe

= I mef=

2eI p Vh

=

TRIANGLE OF METROLOGICAL MESOSCOPIC EFFECTS

f

single electronpump

2eI p Vh

=

revisionof SI system

ATOMIC CLOCK

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UNIVERSAL AND MICROSCOPICCONSTANTS

UNIVERSALQUANTUM

CONSTANTSEMERGE

ROBUSTLY IN METROLOGICAL

TRIANGLE

from S. Harris

ARTIFICIAL ATOMS?

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AN ARTIFICIAL ATOM:THE COOPER PAIR BOX

U

GATEELECTRODE SUPERCONDUCTING

ELECTRODE(“ISLAND”)

SUPER-CONDUCTINGRESERVOIR

TUNNEL JUNCTION(1nm thick)

WITH n PAIRSOF EXCESSELECTRONS

V. Bouchiat et al. 1997

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MECHANICALANALOG

dα/dtdβ/dt

nU

ELECTRICITY MECHANICS

current force

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0

2

1

4

3

STATE 0

STATE 1

COHERENTSUPER-

POSITIONOF

0 AND 1

QUBIT : QUANTUM BINARYINFORMATION UNIT

ENERGY

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time

"NOT"force

"(NOT)1/2 "

WRITINGA SUPER-POSITION

"(NOT)-1/2 "

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THE PRINCIPLE OF INFORMATIONRESTRICTION TAKES ITS TOLL

DURING READOUT,QUANTUM INFORMATION

REDUCES TO0 OR 1

0

1

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gate

1 QUBIT NANO-CIRCUIT

500 nm

island

box junction

electrontrap

readout junction

gate

siliconsubstrate

Vion et al., 2002

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mK GHz07-0-36

QUBIT MANIPULATION

• RESET• IRRADIATION WHILE t• MEASUREMENT

AP

P. P

OLA

RIZ

ATI

ON

t (ns)

Rabi oscillations ofatomic physicsand nuclear

magnetic resonanceoberved on a

single spin!

(Siddiqi et al., 2006)

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CONCLUSIONS AND PERSPECTIVESNEW CHALLENGES : NANOMETER SCALE FABRICATION,

MEASUREMENT OF INDIVIDUAL QUANTAS, THEORY OF COMPLEXQUANTUM SYSTEMS

DISCOVERY OF A NEW COMPLEXITY AXISTOWARDS WHICH QUANTUM MECHANICS

WOULD PRESENT ANOMALIES?

APPLICATIONS: REDEFINITION OF BASIC UNITS, DETECTION OFPARTICLES AND WEAK FORCES, INFORMATION PROCESSING

MESOSCOPIC SYSTEMS OPEN THE WAY TO THEQUANTUM MACHINES IMAGINED BY RICHARD FEYNMAN

NEW QUANTUM EFFECTS : FRACTIONAL CHARGES STRONG COUPLING BETWEEN CHARGE AND FIELD,

LOCAL MANIPULATION OF ELECTRONIC AND NUCLEAR SPINS,NON-GAUSSIAN NOISE, ENTANGLEMENT OF COLLECTIVE VARIABLES....

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MY MENTORS AND CLOSE COLLEAGUESUniversity of Orsay

John ELANDSydney LEACH

Maurice CHAPELLIER

CEA-SaclayAnatole ABRAGAM

Neil SULLIVANMaurice GOLDMANAndré LANDESMAN

U.C. BerkeleyJohn CLARKE

TU DelftHans MOOIJ

Cees DEKKER Sander TANS

Quantronics Group

Daniel ESTEVECristian URBINAEmmanuel TURLOTHugues POTHIERPhilippe JOYEZPief ORFILAPhilippe LAFARGEDenis VION

Vincent BOUCHIATSophie GUERONFrédéric PIERRERonald CRONAbdel AASSIMEAudrey COTTETAnne ANTHOREPatrice BERTET

YaleIrfan SIDDIQIRajamani VIJAYFrédéric PIERREChad RIGETTIEtienne BOAKNINMichael METCALFE

Rob SCHOELKOPFDan PROBERSteve GIRVINDoug STONELuigi FRUNZIOVlad MANUCHARIAN

FreiburgHermann GRABERT U.C. Santa Barbara : John MARTINIS

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W.M. KECK

Research sponsored by :