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slide1
Quantum Reality

Avshalom C. Elitzur

Outline

  • The Nature of Classical light
  • Light going Quantum
  • Universal Duality
  • Quantum Non-Locality
  • Mysteries and Potential Applications

Copyleft – All Rights Reversed Permission is granted to everyone to copy and/or use this work or any part of it.

slide2

Determinism: An extremely Powerful Idea

Philosophiae Naturalis Principia Mathematica (1687)

slide3

Philosophiae Naturalis Principia Mathematica (1687)

In every physical state, given the relevant law and initial conditions, it is possible to predict other states at any time in the past or future.

Earth’s gravitational constant

initial height

time

what s light
What’s light?

It’s made of particles

I. Newton, 1643-1727

what s light1
What’s light?

It’s made of waves

C. Huygens, 1629-1695

light then is
Light, then, is…

Waves!!!

Waves!!

Waves!!

Waves!

Particles!!!

Particles!!

Particles!!

Particles!

slide9

Why does the light ray widen after passing a slit?

diffraction!!!

Diffraction!!

dispersal!!!

diffraction!

dispersal!

diffraction!

dispersal!

dispersal!

what s light2
What’s light?

It’s waves

(I conducted a simple experiment)

He’s right

(I proved it’s electromagnetism)

T. Young, 1773-1829

J. C. Maxwell, 1831-1879

slide11

crest

trough

“in phase”

crest

constructive

interference

trough

Classical Interference

crest

trough

destructive

interference

“out of phase”

crest

trough

the double slit experiment
The Double-Slit Experiment

Water waves interference

slide13

Interference of Water Waves(Courtesy of Tel-Aviv Municipality)

Constructive interference

Destructive

Constructive

the double slit experiment1
The Double-Slit Experiment

Light interference

slide16

And Welcome…

George Koch

slide17

The Father of Quantum Mechanics

M. Planck

1858-1947

Energy comes in discrete units

what s light3
What’s light?

It’s particles

(they gave me the Nobel for that)

what s light5
What’s light?

Waves, eh?

Newton

1 Quantum

1 Quantum

slide24

Confused? Don’t worry!

It will soon become much worse…

what s matter
What’s Matter?

It’s waves

(They gave me a Nobel too)

L. de Broglie (1892-1987)

what s matter1
What’s Matter?

In the solar system, planets can move in any orbit

Why?

In the atom, electrons can move only in certain orbits

what s matter2
What’s Matter?

Electrons revolve only in orbits where waves can reside

what s matter3
What’s Matter?

Hence, you can demonstrate interference with

  • Photons
  • Electrons
  • Protons
  • Neutrons (Zeilinger)
  • Atoms (Zeilinger)
  • Molecules (Zeilinger)
  • ... (Zeilinger?)
slide29

Le travail de Louis de Broglie a fait une grande impression sur moi; il a levé un coin du grand voile (he has lifted the corner of a great veil).

O la la…

Einstein

Langevin

what s light matter1
What’s light/matter?

ErwinSchrödinger (1887-1961)

the famous dialogue
The Famous Dialogue

Niels Bohr (1885-1962)

slide34

A harmless thought experiment:

Where’s the single photon before being detected?

detector

detector

50%

50%

half-silvered mirror

light source

the mach zehnder interferometer
The Mach-Zehnder Interferometer:

detectors

C

D

half-silvered mirrors

solid mirrors

light source

the mach zehnder interferometer1
The Mach-Zehnder Interferometer:
  • Light-ray is emitted and split into two: The reflected half undergoes phase-reflection, while the transmitted half undergoes phase-shift.
  • Two halves reflected back (plus phase )
  • One half split again
  • Second half split again (at the same time)
  • Destructive interference on detector D
  • Constructive interference on detector C
  • All light reaches detector C.

C

D

the mach zehnder interferometer2
The Mach-Zehnder Interferometer:
  • Photon is emitted and split into two
  • Reflected back (notice phase shift upon reflection!)
  • One half split again
  • Second half split again (at the same time)
  • Destructive Interference on detector D
  • Constructive Interference on detector C
  • All light reaches detector C.

C

D

slide38

Confused? Don’t worry:

It will soon get much worse.

Interference occurs with single

Can we outsmart the “which path” uncertainty?

  • Photons
  • Electrons
  • Neutrons
  • Atoms
  • Molecules

Interference

0%

100%

1

0

1

0

50%

slide43

Can we outsmart the “which path” uncertainty? No, but

Nam et Ipsa

Ignorantia

Scientia

Potestas Est

slide44
עיקרון אי-הוודאות: "דע מאין באת – או לאן אתה הולך"(אבל לא שניהם)

0%

100%

50%

0%

100%

50%

אין התאבכות

יש התאבכות

50%

50%

what if we place only one detector
What if we place only one detector?
  • In 50% of the cases a click will sound,
  • I.e., the photon has taken the right path,
  • hence, by the uncertainty principle, interference must be destroyed.
  • But in 50% cases no click will occur,
  • hence the photon took left.
  • Will interference be destroyed too? (Clue: Elitzur hasn’t been awarded the Nobel for disproving the uncertainty principle )
  • For comparison: Suppose the single detector’s battery is off: Will a click be sound? Will interference be destroyed?
  • We must therefore distinguish between two negative results:
  • The classical one (no battery, no click, interference remains intact) should be called Nothing.
  • Whereas the quantum one (battery present, no click, interference destroyed) should be called…
  • Gurnisht.

...

Click!

the epr bell experiment

x

x

x

The EPR – Bell experiment

Spin

Turning the magnets byan angle :

Stern Gerlach

P =Cos2(2)

P =1-Cos2(2)

the epr bell experiment1

x

x

x

x

The EPR – Bell experiment
  • EPR system:
  • The two particles’ spin is always correlated (opposite)
  • Unless we rotate one of the magnets
epr bell experiment
EPR – Bell experiment
  • Rotate right hand magnet by 300:Spin correlations drop to 75%
  • Rotate left hand magnet by 300:Spin correlations drop to 75%
  • Rotating the two magnets in opposite directions: Spin correlations drop to…
  • 25%!
  • No realist explanation without action at a distance
epr bell experiment1
EPR – Bell experiment

00

100%

00

100%

300

300

300-

300-

100%

75%

300

00

75%

300-

00

00

75%

300

300-

00

75%

300-

25%

300

25%

300-

300

slide55

YakirAharonov

Lev Vaidman

Benni Reznik

Sandu Popescu

AvshalomElitzur

Daniel Rohrlich

Jeff Tollaksen

David Albert

BoazTamir

OrSela

Shahar Dolev

Doron Grossman

Einav Friedman

ShayBen Moshe

EliahuCohen

quantum paradoxes
Quantum Paradoxes
  • The Wave-Particle Duality
  • The Quantum-Classical Limit
  • Quantum Non-Locality
attempts at resolution
Attempts at Resolution
  • Copenhagen: Bohr, Heisenberg, Wheeler
  • Hidden Variables: de Broglie, Bohm
  • Consciousness: von Neumann, Wigner
  • Many Worlds: Everett, Wheeler
  • Retrocausal Models: Aharonov, Cramer

Scientific Alternatives

Spontaneous Collapse: Ghirardi, Rimini & Weber

Decoherence: Zurek

Gravity: Penrose

quantum technology
Quantum Technology
  • Quantum Chemistry
  • Quantum Optics
  • Transistors
  • Quantum Cryptography
  • Quantum Computation
  • Quantum Imaging
  • Quantum Teleportation
broader implications
Broader Implications
  • Quantum Cosmology
  • Quantum Biology?
  • Quantum Mind?
slide60

Quo Vadis Quantum Mechanics?

A. C. Elitzur, S. Dolev & N. Kolenda, EdsSpringer Verlag, 2005

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