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CALTECH ESTABLISHES IQI
Insitute
for Quantum Information
by John Preskill
Fall
2001
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The Divisions of Physics, Mathematics, and Astronomy (PMA) and
Engineering and Applied Science have jointly established the Institute
for Quantum Information (IQI), supported by a five-year grant
from the National Science Foundation. The goal of the IQI is to
advance the foundations of quantum information science (QIS),
an emerging field that draws on physics, mathematics, computer
science, and engineering. Broadly speaking, QIS addresses how
the principles of quantum physics can be harnessed to improve
the acquisition, transmission, and processing of information.
 Graduate
students (left to right) Andrew Landahl, Jim Harrington, and
Charlene Ahn discussing the finer points of qubits. |
QIS
derives much of its intellectual vitality from three central ideas,
all of relatively recent vintage. The first important idea is
quantum computation. We have learned that a computer that operates
on quantum states instead of classical bits can perform tasks
that are beyond the capability of any conceivable classical computer.
For example, finding the 200-digit prime factors of a 400-digit
composite number would take billions of years on today's supercomputers.
But for a quantum computer it would be an easy problem, not much
harder than multiplying two numbers together to find their product.
The boundary between "hard" and "easy"—between
problems that someday will be solved and problems that never can
be solved—is essentially different in a quantum world than
in a classical world.
| Aside
from its technological implications, QIS is an intellectually
stimulating basic research field. Fundamental questions such
as What is the computational power of Nature?, Can measurement
be reversed?, and How much information can we learn? drive
the field and inspire new research directions. |
The
second important idea is quantum cryptography. You can communicate
privately with another party over the Internet, but the security
of that communication is founded on assumptions about the computational
resources that are available to a potential adversary. In contrast,
if you were able to communicate by transmitting quantum states
(like photon wave packets traveling in an optical fiber) instead
of classical bits, you could achieve a higher level of privacy
founded on fundamental laws of physics. Quantum cryptography is
based on the principle that it is impossible to collect information
about the state of a quantum system without disturbing the state
in a detectable way.
The
third important idea is quantum error correction, which has greatly
boosted our confidence that large-scale quantum computers really
can be built and operated someday. The power of a quantum computer
derives from its ability to process coherent quantum states, but
such states are very easily damaged by uncontrolled interactions
with the environment—a process called decoherence. Thus,
quantum computers are much more susceptible to error than conventional
digital computers. But we have learned that quantum states can
be cleverly encoded so that the debilitating effects of decoherence,
if not too severe, can be resisted. In principle then, even very
intricate quantum systems can be stabilized and accurately controlled.
| "As
with any revolutionary scientific insight, the long-term implications
[of QIS] cannot be clearly anticipated, but we are confident
that they will be profound. We also expect that the emergence
of QIS will have an extensive eventual impact on how science
is taught at the college and secondary level, and will bring
a deeper understanding of quantum physics to a broad segment
of the lay public." —John Preskill, Professor
of Theoretical Physics |
The
scientific mission of the IQI is to elaborate and develop these
ideas, and to otherwise illuminate the essential differences between
quantum information and classical information. We aim to better
understand the capabilities of quantum computers and to bridge
the vast gap between the theory and practice of quantum information
processing by conceiving new approaches to the physical manipulation
of coherent quantum states.
A
variety of Caltech groups in both the EAS and PMA Divisions have
been engaged in QIS research for several years. The IQI consolidates,
expands, and enhances these activities by providing a focal point
for QIS research on the Caltech campus. Faculty, research staff,
and students from both Divisions interact, promoting the communication
and collaboration across disciplinary boundaries that will be
essential to the further development of the field.
Central
to the IQI's scientific program is a vigorous visitor's program
that brings the world leaders of the QIS research community to
Caltech for both long-term and short-term visits. Almost 40 visitors
from the international research community have spent anywhere
from several days to several months in residence at IQI since
its inception. The IQI also supports post-doctoral scholars drawn
from backgrounds spanning the disciplines relating to QIS. The
visitors and postdocs affiliated with the IQI occupy space in
the Steele and Jorgensen laboratories.
EAS
faculty connected with the IQI include John Doyle, Professor of
Electrical Engineering; Michelle Effros, Associate Professor of
Electrical Engineering; Axel Scherer, Neches Professor of Electrical
Engineering, Applied Physics, and Physics; Leonard Schulman, Associate
Professor of Computer Science. PMA faculty include Jeff Kimble,
Valentine Professor and Professor of Physics; Hideo Mabuchi (PhD
'98), Associate Professor of Physics; John Preskill, Professor
of Theoretical Physics; Michael Roukes, Professor of Physics;
and Kip Thorne (BS '62), Feynman Professor of Theoretical Physics.
In
the 21st century, information technology will play an increasingly
important role in our daily lives. We also anticipate that thinking
about how information can be encoded and processed will facilitate
progress in basic science. Though quantum theory is now over 100
years old, we are just beginning to learn some of the profound
ways in which quantum information differs from classical information.
The IQI aims to lead the quest for a deeper understanding of the
role of information in fundamental physics.
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