317
See also: Albert Einstein 214–21 ■ Erwin Schrödinger 226–33 ■
Alan Turing 252–53 ■ Hugh Everett III 284–85Q
uantum information
processing is one of the
newest fields in quantum
mechanics. It operates in a
fundamentally different way from
conventional computing. The
Russian-German mathematician
Yuri Manin was among the very
first pioneers developing the theory.
The bit is the fundamental
carrier of information in a
computer, and can exist in two
states: 0 and 1. The fundamental
unit of information in quantum
computing is called a qubit. It ismade of “trapped” subatomic
particles, and also has two possible
states. An electron, for example,
can be spin-up or spin-down, and
photons of light can be polarized
horizontally or vertically. However,
the quantum mechanical wave
function allows qubits to
exist in a superposition of both
states, increasing the amount of
information that they can carry.
Quantum theory also permits
qubits to become “entangled,”
which exponentially increases the
data carried with each additional
qubit. This parallel processing
could theoretically produce
extraordinary computing power.Demonstrating the theory
First aired in the 1980s, quantum
computers seemed just theoretical.
However, calculations have recently
been achieved on arrays with only
a few qubits. To provide a useful
machine, quantum computers must
achieve hundreds or thousands of
entangled qubits, and there are
problems scaling up to this size.
Work on these problems continues. ■FUNDAMENTAL BUILDING BLOCKS
A OUANTUM
MODEL OF
COMPUTING
YURI MANIN (1937–)
IN CONTEXT
BRANCH
Computer science
BEFORE
1935 Albert Einstein, Boris
Podolsky, and Nathan Rosen
develop the “EPR paradox,”
providing the first description
of quantum entanglement.
AFTER
1994 American mathematician
Peter Shor develops an
algorithm that can achieve
the factorization of numbers
using quantum computers.
1998 Using Hugh Everett’s
many-worlds interpretation of
quantum mechanics, theorists
imagine a superposition state
in which a quantum computer
is both on and off.
2011 A research team from
the University of Science
and Technology in Hefei,
China, correctly finds the
prime factors of 143 using a
quantum array of four qubits.
The information on a qubit can
be represented as any point on the
surface of a sphere—a 0, a 1, or a
superposition of the two.01