Quantum Reality
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Quantum reality

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.


Quantum reality

Determinism: An extremely Powerful Idea

Philosophiae Naturalis Principia Mathematica (1687)


Quantum reality

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!


Quantum reality

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


Quantum reality

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


Quantum reality

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

Constructive interference

Destructive

Constructive


The double slit experiment1

The Double-Slit Experiment

Light interference


Quantum reality

Farewell Classical Physics


Quantum reality

And Welcome…

George Koch


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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 light4

What’s light?


What s light5

What’s light?

Waves, eh?

Newton

1 Quantum

1 Quantum


What s light6

What’s light?

1 Quantum


What s light7

What’s light?


What s light8

What’s light?


Quantum reality

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?)


Quantum reality

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


The wave particle duality

The Wave-Particle Duality


What s light matter

What’s light/matter?


What s light matter1

What’s light/matter?

ErwinSchrödinger (1887-1961)


The famous dialogue

The Famous Dialogue

Niels Bohr (1885-1962)


Quantum reality

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


Quantum reality

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%


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Can we outsmart the “which path” uncertainty?

Interference

0%

100%

50%


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Can we outsmart the “which path” uncertainty?

50%

50%

50%


Quantum reality

Can we outsmart the “which path” uncertainty?

50%

50%

50%


Quantum reality

Can we outsmart the “which path” uncertainty?

Interference

0%

100%


Quantum reality

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

Nam et Ipsa

Ignorantia

Scientia

Potestas Est


Quantum reality

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!


Quantum reality

Can we outsmart the uncertainty principle?

Yes we can!


Quantum reality

Aharonov’s “weak measurement


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


Quantum reality

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?


Quantum reality

Quo Vadis Quantum Mechanics?

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


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