Quantum Reading

Looking to do some reading? Here’s a selection of articles to get you started. If you’re looking to invest more time and mental energy, choose one from our recommended crop of popular science books on the quantum world.

Articles

You’ll find the latest news and articles in Scientific American’s section devoted to quantum physics:
http://www.scientificamerican.com/topic.cfm?id=quantum-physics

CQT has its own quantum briefing room:
http://www.quantumlah.org/main/forpublic.php

Here’s “Quantum Computing 101″ from the Institute for Quantum Computing in Waterloo, Canada:
http://iqc.uwaterloo.ca/welcome/quantum-computing-101

New Scientist magazine offers a guide to the Quantum World:
http://www.newscientist.com/article/dn9930-introduction-quantum-world.ht...

CQT’s director, Artur Ekert, on quantum cryptography:
http://plus.maths.org/content/os/issue35/features/ekert/index

A poster on what quantum computing is all about:
http://www.qi.damtp.cam.ac.uk/sites/default/files/OD2_WhatareQCs.gif

Science writer John Gribbin offers his take on some quantum mysteries:
http://www.lifesci.sussex.ac.uk/home/John_Gribbin/quantum.htm

New York Times writer John Markoff discusses the emergence of quantum computing:
http://www.nytimes.com/2010/11/09/science/09compute.html

A feature in Scientific American explores the boundary between the quantum and classical worlds:
http://www.scientificamerican.com/article.cfm?id=bringing-schrodingers-q...

Vlatko Vedral asks if we can find those pesky parallel universes:
http://www.fqxi.org/community/forum/topic/266

A lovely introduction to the spooky phenomenon that is quantum entanglement:
http://www.qubit.org/tutorials/19-quantum-entanglement.html

Here’s a slightly more technical introduction (warning: equations ahead!) with links to pages that deal with all the main aspects of quantum theory:
http://www.ipod.org.uk/reality/reality_quantum_intro.asp

Another general look at the theory:
http://www.quantumintro.com/

Books

Why not find a quantum book that suits you? Here are some reviews of good books about quantum theory:

Entanglement by Amir Aczel
http://www.americanscientist.org/bookshelf/pub/think-nonlocally

Quantum by Jim Al-Khalili
http://www.goodreads.com/book/show/100034.Quantum

Quantum Theory Cannot Hurt You by Marcus Chown
http://www.independent.co.uk/arts-entertainment/books/reviews/paperbacks...

The Quantum Universe: Everything That Can Happen Does Happen by Brian Cox and Jeff Forshaw
http://www.newscientist.com/blogs/culturelab/2011/11/quantum-mechanics-d...

The Age of Entanglement: When Quantum Physics Was Reborn by Louisa Gilder
http://www.goodreads.com/book/show/5096882-the-age-of-entanglement

Genius: The Life and Science of Richard Feynman by James Gleick
http://www.goodreads.com/book/show/98685.Genius

Erwin Schrodinger and the Quantum Revolution by John Gribbin
http://www.telegraph.co.uk/culture/books/bookreviews/9188438/Erwin-Schro...

Strange Beauty: Murray Gell-Mann and the Revolution in Twentieth-Century Physics by George Johnson
http://www.goodreads.com/book/show/258459.Strange_Beauty

Quantum by Manjit Kumar
http://www.guardian.co.uk/books/2008/nov/15/quantum-physics-einstein-boh...

Programming the Universe: A Quantum Computer Scientist Takes on the Cosmos by Seth Lloyd
http://www.arturekert.org/Site/Lloyd.html

A Brilliant Darkness by Joao Magueijo
http://www.newscientist.com/blogs/culturelab/2010/01/cracking-the-majora...

How to Teach Quantum Physics to Your Dog by Chad Orzel
http://www.timeshighereducation.co.uk/story.asp?storycode=413835

Knocking on Heaven’s Door by Lisa Randall
http://www.newscientist.com/blogs/culturelab/2011/09/an-insiders-guide-t...

Quantum Physics – A first Encounter by Valerio Scarani
http://www.goodreads.com/book/show/100028.Quantum_Physics

Decoding Reality by Vlatko Vedral
http://www.newscientist.com/blogs/culturelab/2010/03/the-universe-is-a-q...

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Quantum Theories

Q is for ... Quantum biology

A new and growing field that explores whether many biological processes depend on uniquely quantum processes to work. Under particular scrutiny at the moment are photosynthesis, smell and the navigation of migratory birds.

T is for ... Tunnelling

This happens when quantum objects “borrow” energy in order to bypass an obstacle such as a gap in an electrical circuit. It is possible thanks to the uncertainty principle, and enables quantum particles to do things other particles can’t.

E is for ... Entanglement

When two quantum objects interact, the information they contain becomes shared. This can result in a kind of link between them, where an action performed on one will affect the outcome of an action performed on the other. This “entanglement” applies even if the two particles are half a universe apart.

S is for ... Superposition

Quantum objects can exist in two or more states at once: an electron in superposition, for example, can simultaneously move clockwise and anticlockwise around a ring-shaped conductor.

B is for ... Bell's Theorem

In 1964, John Bell came up with a way of testing whether quantum theory was a true reflection of reality. In 1982, the results came in – and the world has never been the same since!

W is for ... Wavefunction

The mathematics of quantum theory associates each quantum object with a wavefunction that appears in the Schrödinger equation and gives the probability of finding it in any given state.

A is for ... Act of observation

Some people believe this changes everything in the quantum world, even bringing things into existence.

C is for ... Computing

The rules of the quantum world mean that we can process information much faster than is possible using the computers we use now.

Z is for ... Zero-point energy

Even at absolute zero, the lowest temperature possible, nothing has zero energy. In these conditions, particles and fields are in their lowest energy state, with an energy proportional to Planck’s constant.

Y is for ... Young's Double Slit Experiment

In 1801, Thomas Young proved light was a wave, and overthrew Newton’s idea that light was a “corpuscle”.

C is for ... Cryptography

People have been hiding information in messages for millennia, but the quantum world provides a whole new way to do it.

V is for ... Virtual particles

Quantum theory’s uncertainty principle says that since not even empty space can have zero energy, the universe is fizzing with particle-antiparticle pairs that pop in and out of existence. These “virtual” particles are the source of Hawking radiation.

F is for ... Free Will

Ideas at the heart of quantum theory, to do with randomness and the character of the molecules that make up the physical matter of our brains, lead some researchers to suggest humans can’t have free will.

G is for ... Gravity

Our best theory of gravity no longer belongs to Isaac Newton. It’s Einstein’s General Theory of Relativity. There’s just one problem: it is incompatible with quantum theory. The effort to tie the two together provides the greatest challenge to physics in the 21st century.

R is for ... Radioactivity

The atoms of a radioactive substance break apart, emitting particles. It is impossible to predict when the next particle will be emitted as it happens at random. All we can do is give the probability that any particular atom will have decayed by a given time.

H is for ... Hawking Radiation

In 1975, Stephen Hawking showed that the principles of quantum mechanics would mean that a black hole emits a slow stream of particles and would eventually evaporate.

D is for ... Dice

Albert Einstein decided quantum theory couldn’t be right because its reliance on probability means everything is a result of chance. “God doesn’t play dice with the world,” he said.

A is for ... Alice and Bob

In quantum experiments, these are the names traditionally given to the people transmitting and receiving information. In quantum cryptography, an eavesdropper called Eve tries to intercept the information.

U is for ... Universe

To many researchers, the universe behaves like a gigantic quantum computer that is busy processing all the information it contains.

B is for ... Bose-Einstein Condensate (BEC)

At extremely low temperatures, quantum rules mean that atoms can come together and behave as if they are one giant super-atom.

P is for ... Planck's Constant

This is one of the universal constants of nature, and relates the energy of a single quantum of radiation to its frequency. It is central to quantum theory and appears in many important formulae, including the Schrödinger Equation.

I is for ... Information

Many researchers working in quantum theory believe that information is the most fundamental building block of reality.

N is for ... Nonlocality

When two quantum particles are entangled, it can also be said they are “nonlocal”: their physical proximity does not affect the way their quantum states are linked.

W is for ... Wave-particle duality

It is possible to describe an atom, an electron, or a photon as either a wave or a particle. In reality, they are both: a wave and a particle.

R is for ... Randomness

Unpredictability lies at the heart of quantum mechanics. It bothered Einstein, but it also bothers the Dalai Lama.

D is for ... Decoherence

Unless it is carefully isolated, a quantum system will “leak” information into its surroundings. This can destroy delicate states such as superposition and entanglement.

M is for ... Multiverse

Our most successful theories of cosmology suggest that our universe is one of many universes that bubble off from one another. It’s not clear whether it will ever be possible to detect these other universes.

A is for ... Atom

This is the basic building block of matter that creates the world of chemical elements – although it is made up of more fundamental particles.

K is for ... Kaon

These are particles that carry a quantum property called strangeness. Some fundamental particles have the property known as charm!

Q is for ... Qubit

One quantum bit of information is known as a qubit (pronounced Q-bit). The ability of quantum particles to exist in many different states at once means a single quantum object can represent multiple qubits at once, opening up the possibility of extremely fast information processing.

S is for ... Schrödinger’s Cat

A hypothetical experiment in which a cat kept in a closed box can be alive and dead at the same time – as long as nobody lifts the lid to take a look.

U is for ... Uncertainty Principle

One of the most famous ideas in science, this declares that it is impossible to know all the physical attributes of a quantum particle or system simultaneously.

L is for ... Large Hadron Collider (LHC)

At CERN in Geneva, Switzerland, this machine is smashing apart particles in order to discover their constituent parts and the quantum laws that govern their behaviour.

M is for ... Many Worlds Theory

Some researchers think the best way to explain the strange characteristics of the quantum world is to allow that each quantum event creates a new universe.

L is for ... Light

We used to believe light was a wave, then we discovered it had the properties of a particle that we call a photon. Now we know it, like all elementary quantum objects, is both a wave and a particle!

S is for ... Schrödinger Equation

This is the central equation of quantum theory, and describes how any quantum system will behave, and how its observable qualities are likely to manifest in an experiment.

P is for ... Probability

Quantum mechanics is a probabilistic theory: it does not give definite answers, but only the probability that an experiment will come up with a particular answer. This was the source of Einstein’s objection that God “does not play dice” with the universe.

T is for ... Teleportation

Quantum tricks allow a particle to be transported from one location to another without passing through the intervening space – or that’s how it appears. The reality is that the process is more like faxing, where the information held by one particle is written onto a distant particle.

J is for ... Josephson Junction

This is a narrow constriction in a ring of superconductor. Current can only move around the ring because of quantum laws; the apparatus provides a neat way to investigate the properties of quantum mechanics.

R is for ... Reality

Since the predictions of quantum theory have been right in every experiment ever done, many researchers think it is the best guide we have to the nature of reality. Unfortunately, that still leaves room for plenty of ideas about what reality really is!

I is for ... Interferometer

Some of the strangest characteristics of quantum theory can be demonstrated by firing a photon into an interferometer: the device’s output is a pattern that can only be explained by the photon passing simultaneously through two widely-separated slits.

O is for ... Objective reality

Niels Bohr, one of the founding fathers of quantum physics, said there is no such thing as objective reality. All we can talk about, he said, is the results of measurements we make.

X is for ... X-ray

In 1923 Arthur Compton shone X-rays onto a block of graphite and found that they bounced off with their energy reduced exactly as would be expected if they were composed of particles colliding with electrons in the graphite. This was the first indication of radiation’s particle-like nature.

H is for ... Hidden Variables

One school of thought says that the strangeness of quantum theory can be put down to a lack of information; if we could find the “hidden variables” the mysteries would all go away.

G is for ... Gluon

These elementary particles hold together the quarks that lie at the heart of matter.