A. S. Holevo. An Introduction to Quantum Information
Theory (In Russian).
Moscow Center of
Continuous Mathematical Education (MCCME), Moscow 2002.
Some
50 years ago two revolutionary discoveries were made,
which
to a great extent determined the image of the contemporary
world.
These were -- invention of transistor,
opening way
to miniaturization of digital
computers and radical reduction of
material and
power expenses in information processing systems, and
-- creation of
the mathematical foundations of information theory,
giving the principles of
rational and reliable design of such
systems and arrays of data.
At present we are witnessing
emergence of
theoretical and experimental foundations of the
quantum information science. Principles of
quantum
cryptography were already practically implemented
and
successfully demonstrated.
Under discussion is the idea of
quantum computer, promising
overwhelming perspectives (a
practical
realization of this project, however, would require a
technological
revolution comparable with the discovery of
transistor.)
Independently of how soon such an ambitious project
could be realized, the
quantum information theory represents a new
exciting field
of key importance to a number of fundamental
problems,
which up to recent time were out of the scope of
scientific
research. It also stimulates the development of
experimental techniques
and high precision technologies for
manipulation of microsystems, potentially
important for new
efficient applications.
A central result of the classical
information theory is coding
theorem, establishing
the possibility of reliable data transmission and
processing
at the rates not exceeding the definite value
(capacity ) characterizing the
given information processing
system (for definiteness one speaks of a
(communication
channel). The issue of the information
capacity of quantum
communication channels arose soon after publication of the
pioneering
Shannon's paper and goes back
to even earlier classical papers of
Gabor and Brillouin, asking for
fundamental physical limits on the
rate and quality of information
transmission. This work laid a
physical foundation and raised the question of
consistent quantum
information treatment of the problem. Important steps in
this
direction were made in the seventies when quantum statistical
decision
(detection and estimation) theory was created,
making a quantum
probabilistic frame for this circle of problems.
At that time the quantum
entropy bound and strict superadditivity
of classical information in quantum
communication channels were
established.
A substantial progress has been achieved during
the past years, when a number
of quantum coding theorems was
discovered, proving the achievability
of the entropy bound.
Moreover, it was realized that quantum channel is
characterized by
the whole spectrum of capacities depending on the nature
of the
information resources and the specific protocols used for
the
transmission. To a great extent this progress was
stimulated by an interplay
between the quantum communication
theory and quantum information ideas
related to recent development
in quantum computing. This new age
of quantum information
science
is characterized by emphasis to the new
possibilities (rather than restrictions)
opened by the quantum
nature of the information processing agent.
On the other hand,
the
question of information capacity is important for the theory
of quantum
computer, particularly in connection with quantum
error-correcting codes,
communication and algorithmic complexities
and a number of other important issues.
This book is intended
to give a systematic, self-contained and rigorous
treatment of the
aspects of quantum information theory related to the notion of
quantum
communication channels and their capacities. It is
preceeded with
a detailed introduction to the statistical
structure of quantum theory
providing a general basis for quantum
probability, statistics and information,
therefore a reader need
not have a profound preliminary background in quantum
mechanics.
Knowledge of basic mathematical courses will suffice. The book
was
not aimed to be all-embracing: e. g., we do not touch quantum
cryptography and
entanglement quantification, which now undergo
fast development,
and our consideration of quantum computing is
quite fragmentary. An
interested reader can find discussion
of these problems in other sources
given in the references; on the
other hand, a reader will find some topics in our
lectures,
such as e.g. entanglement-assisted classical communication,
not
covered by other books. Further, this book is addressed to a
more
mathematically oriented reader and are more concise.
The
proofs of several simple auxiliary results
in the lectures are
left as a useful exercise; on the other hand, we emphasize
a
number of important open problems still awaiting for their solution.