New Scientist Essential Guide 5 2020 Quantum Physics.pdf

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ESSENTIAL
GUIDE№5
ORIGINS OF QUANTUM THEORY
HOW THE QUANTUM WORLD WORKS
QUANTUM TECHNOLOGIES
THE SEARCH FOR EVEN
BETTER THEORIES
AND MORE
QUANTUM
PHYSICS
THE INSIDE TRACK
ON OUR GREATEST
AND WEIRDEST
THEORY OF REALITY
EDITED BY
MICHAEL BROOKS
NEW
SCIENTIST
ESSENTIAL
GUIDE
QUANTUM
PHYSICS
O ONE understands quantum mechanics”.
Many who have attempted to get to grips
with our most basic theory of the workings
of material reality would nod vigorously at
this quote from Nobel laureate (and
quantum and particle physicist) Richard
Feynman. With its dead-and-alive cats, particles in
multiple places at once, spooky influences travelling
over distances and strange implication that we all,
somehow, might as observers be implicated in the
fabrication of reality, the assaults of quantum theory
on our intuition are legion, and legendary.
Still, nothing ventured, nothing gained. This fifth
New Scientist Essential Guide
aims to be a primer of
what we do know: how quantum theory came to be,
how it fits together and the problems it presents, as well
as giving perspectives on technological advances it is
bringing in the realms of quantum computing, and
what better theories might lie beyond quantum theory.
I hope you find it a stimulating read; feedback is
welcome at essentialguides@newscientist.com. Just
remember, if you don’t arrive at a full understanding of
quantum physics over these 96 pages, at least you’re in
very good company.
Michael Brooks
NEW SCIENTIST ESSENTIAL GUIDES
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NEW SCIENTIST ESSENTIAL GUIDES
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ESSENTIAL GUIDES
SERIES EDITOR
Richard Webb
DESIGN
Craig Mackie
SUBEDITOR
Hannah Joshua
PRODUCTION AND APP
Joanne Keogh
TECHNICAL DEVELOPMENT (APP)
Amardeep Sian
PUBLISHER
Nina Wright
EDITOR-IN-CHIEF
Emily Wilson
DISPLAY ADVERTISING
+44 (0)20 7611 1291
displayads@newscientist.com
ABOUT THE EDITOR
Michael Brooks is a science writer,
New Scientist
consultant and
author of books including
Can We Travel Through Time?
and
The Quantum
Astrologer’s Handbook.
He has a PhD in quantum physics
ADDITIONAL CONTRIBUTORS
Gilead Amit, Anil Ananthaswamy, Jim Baggott, Philip Ball,
Jon Cartwright, Matthew Chalmers, Marcus Chown, Stuart Clark,
Daniel Cossins, Leah Crane, Ciarán Gilligan-Lee, Rowan Hooper, Richard Webb
New Scientist Essential Guide | Quantum Physics |
1
CHAPTER 1
CHAPTER 2
CHAPTER 3
INTO THE
QUANTUM
WORLD
Quantum theory is perhaps the
most rigorously tested theory in all
of science – and yet its random
nature and prediction of weird,
probabilistic effects and spooky
influences challenges our intuitions
about how reality should work.
So how did the theory come to be,
and what does it tell us?
p. 6
The origins of
quantum mechanics
QUANTUM
WEIRDNESS
QUANTUM
AND
REALITY
The fuzzy weirdness of the quantum
world leaves us with a conundrum:
how does our concrete, classical reality
emerge from it? Standard quantum
theory gives a seemingly absurd
answer. Many rival interpretations
attempt to make sense of the problem –
which starts with science’s most
notorious thought experiment.
p. 36
The mystery of Schrödinger’s cat
p. 39
The cat killer: Erwin Schrödinger
p. 40
The de Broglie-Bohm
interpretation
p. 42
Objective collapse
p. 46
Quantum Bayesianism
p. 48
Emergent objective reality
p. 50
The many worlds interpretation
p. 51
Quantum Russian roulette
p. 54
None of the above?
There are many aspects of quantum
theory that challenge our intuition.
The acknowledged zenith of its
weirdness, however, comes in the
phenomenon of entanglement – a link
between distant objects that goes
against all our ingrained notions of
reality and locality, and which was
much derided by one Albert Einstein.
p. 20
“Spooky action at a distance”
p. 22
Quantum duellists:
Niels Bohr and Albert Einstein
p. 24
Loopholes in reality
p. 30
Can effect precede cause?
p. 10
Quantum uncertainty
p. 12
Uncertain genius:
Werner Heisenberg
p. 13
The experiment that
defied reality
p. 16
A timeline of quantum physics
2
| New Scientist Essential Guide | Quantum Physics
CHAPTER 4
CHAPTER 5
CHAPTER 6
QUANTUM
COMPUTING
QUANTUM
AT LARGE
BEYOND
QUANTUM
Transistors, lasers and a host of
other technologies already exploit
basic quantum principles. But it’s in
computing that properties such as
superposition and entanglement look
set to revolutionise things, promising
superfast processors, plus new ways
to both make and break encrypted
messages.
p. 60
What quantum computers are
made of
by Vlatko Vedral
p. 64
Quantum software
p. 65
A timeline of quantum
computing
p. 66
Quantum supremacy
p. 67
The power of quantum
cryptography
p. 70
Quantum-proof numbers
Quantum physics rules the domain of
the very small, but it seems only right
that the fundamental laws of matter
also affect the larger universe that
matter inhabits. We don’t have all the
answers yet, but from the mystery of
flowing time to the intimate secrets
of biology there are many ways the
world could be quantum at heart.
p. 74
The secret life of empty space
by Paul Davies
p. 79
A quantum of time
p. 80
Is life quantum?
Many physicists remain convinced
quantum theory can’t be the final
answer. In part that’s down to its
mysterious nature, but perhaps the
most practical reason to look beyond
it is the way its theory fails to mesh
with Einstein’s general relativity. Two
distinguished physicists give their
take on that knotty problem.
p. 86
A manifesto for a new reality
by Lee Smolin
p. 91
Weirder than weird?
p. 92
Weaving reality’s fabric
by Sean Carroll
New Scientist Essential Guide | Into the quantum world |
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