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Atoms are one of the freakiest objects in the universe. What’s weird is that electrons inside atoms can be
thought of as particles that behave like waves. It’s like saying you have a baseball that doesn’t definitely
exist here or there, but has an indefinite position spread out everywhere, like a wave. From cell phones
and computers to Blu-rayTM and the internet, nature’s ability to unify a wave and a particle has empowered
us to create more cool technology than any other idea in history. Explore why the future is quantum!
What’s the big idea?
Small is different. In the tiny world of atoms,
nature plays by bizarre rules that clash severely
with commonsense. For instance, particles like
electrons behave as if they can be in multiple
places—or be moving in multiple directions—at
the same time. Such remarkable behaviour is
not only fascinating, it’s essential for the very
existence of our day-to-day world.
For example, in the Particle animation we
see the best possible commonsense model
of an atom: electrons behaving like ordinary
particles, orbiting the atomic nucleus like
planets orbit the sun. But this model is terribly
wrong. If electrons moved like that they
would emit electromagnetic waves, as do the
oscillating electrons in a cell phone antenna.
In a cell phone, powering those waves drains
the battery. In an atom, powering those
waves would drain the electrostatic energy
stored between the nucleus and the electrons,
causing the electrons to spiral into the nucleus
and the atom to collapse. In other words,
commonsense leads us to a model of the
atom—and hence rocks, trees and people—
that cannot exist in our universe!
So what does an atom look like? Clearly, an
atomic electron can’t stand still (electrostatic
attraction would just pull it straight into the
nucleus), nor can it move (as it would emit
energy and the atom would collapse). So
what does it do? Here’s a clue: if an electron
was spread out along its orbit, so instead of
a rotating particle it was a rotating ring, then
no electromagnetic waves would be emitted,
and the atom would be stable. Why? Because
waves are created by things that oscillate, and
there’s nothing oscillating about a rotating
ring. A rotating ring of charge would create
static electric and magnetic fields, but no
electromagnetic waves that would carry energy
away from the atom.
So is this what’s happening? Well, not quite,
because whenever we look at an electron, we
always find a whole point-like particle here or
there, never something spread out into a ring,
or any other shape. Instead, the electron is a
particle, but one that does not definitely exist
here or there at any instant of time. It has an
indefinite position that is spread evenly around
its orbit (other spreads of indefinite position are
also possible, but this is the closest quantum
analogue to an orbiting particle). At any instant
of time the electron could potentially be found
anywhere in its orbit, and so, while not literally
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so, it is effectively spread out into a rotating
ring (actually, more of a rotating donut—see the
Quantum Mechanics animation). In essence,
the electron is a particle that behaves as if it is in
many places at once!
and a particle. Atoms work by rules that are
completely alien to our everyday experience with
the world, and yet, atoms underlie every such
experience. It is a fantastic universe we live in!
What’s it good for?
Computers
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What is a xenopus? Google it and you’ll
quickly learn everything there is to know
about this claw-bearing African frog. How
is this frog related to quantum mechanics?
Answer: the internet, which is powered by
computers, which in turn are powered by
quantum mechanics. Computers have not
only dramatically increased our ability to share
This “ghostly” existence is described by a donutshaped wave circulating around the nucleus,
which can circulate either way (see animation).
Moreover, like the two waves moving in opposite
directions in the Wave animation, which combine
to produce a standing wave that is not moving,
a single electron can, in essence, be circulating
both ways simultaneously, and in this way can
be effectively standing still! An electron inside
an atom can move or stand still, but not in any
ordinary sense of these words.
An atom is an extraordinary object, whose very
existence relies on nature’s ability to unify a wave
knowledge, they also allow us to generate
new knowledge—do calculations that wildly
exceed human capacity. Supercomputers
today are able to simulate complex physical
processes on a global scale, in an attempt
to better understand everything from
earthquakes to global warming, and are even
used to simulate the evolution of the entire
universe—from the big bang to the present—
to probe what it is made of and how it works.
The profound positive impact that computers
have had on science, engineering and society
in general is, well, incalculable.
Lasers
Orange juice, 600 mL, $6.53—this information
is obtained from simply passing the container
over the scanning laser at the grocery store.
Laser light is not ordinary light—it’s “quantum
light”: a coherent shower of little packets
of pure energy, called photons, capable of
transmitting information over the internet,
cutting through steel, surgically welding a
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torn retina, playing a Blu-ray Disc , printing
a document or measuring the distance to
the moon. It’s even being used to search
for an answer to our global energy needs.
One of the world’s largest lasers at the
National Ignition Facility in the United States
is attempting to spark miniature suns—to
generate energy through fusion. Imagine a
world with safe, clean, and virtually limitless
energy.
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Cryptography
Imagine the ability to send secret messages
anywhere in the world with absolute security.
A new class of technologies that can detect
eavesdroppers regardless of how clever they
are or how sophisticated their snooping
equipment; a perfect security guaranteed by
the very laws of nature themselves—quantum
laws. These quantum technologies have
already been proven over short distances,
and there are even commercially available
systems. Governments, banks and a host of
other organizations are extremely interested,
with visions of new ways to do commerce and
bolster national security. What’s the next step?
Scientists and engineers have their eyes on
an absolutely secure global satellite quantum
communication network. Welcome to the
quantum information age!
Quantum Computers
Quantum superposition, entanglement, and
teleportation—three ingredients needed for
a quantum computer. What’s a quantum
computer? A new breed of computer that
might make today’s supercomputers look
like mere hand calculators. Instead of
processing bits of information (binary digits, 0
or 1) they would process qubits of quantum
information: quantum superpositions of
both 0 and 1—simultaneously; a new kind
of “quantum parallel” computer. Using
quantum entanglement—one of the weirdest
aspects of quantum mechanics—this quantum
information would be quantum teleported
between different parts of the computer.
Scientists have already built small prototypes,
and know of a few kinds of problems quantum
computers can solve—like quantum database
searching, or breaking the encryption codes
we use today for secure communications. A
huge, worldwide effort is currently underway
attempting to scale up these prototypes and
find new kinds of problems these amazing
machines could solve. If successful, we may be
in for a second computer revolution, possibly
even more profound than the first.
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