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<\/p>\n\n\n\nThe most successful practical applications of quantum mechanics in informa-<\/p>\n\n\n\n
tion theory have been in the \ufb01eld of communication. This is a very old \ufb01eld that<\/p>\n\n\n\n
has taken inputs from engineering, pure mathematics and computer science<\/p>\n\n\n\n
apart from physics. It is only natural that application of quantum techniques<\/p>\n\n\n\n
here should be among the \ufb01rst to be considered and implemented. Modern<\/p>\n\n\n\n
technology in optical communication using laser light and optical \ufb01ber cables<\/p>\n\n\n\n
is su\ufb03ciently advanced that it can quickly be adapted to using photons as the<\/p>\n\n\n\n
quantum carriers of information.<\/p>\n\n\n\n
In analyzing information communication, we normally consider the follow-<\/p>\n\n\n\n
ing areas:<\/p>\n\n\n\n
1. Coding: representing information accurately in terms of physical vari-<\/p>\n\n\n\n
ables and the removal of redundancy leading to more e\ufb03ciency, which<\/p>\n\n\n\n
is known as compression;<\/p>\n\n\n\n
2. Transmission: the information-carrying capacity of a channel and the<\/p>\n\n\n\n
possible errors introduced into the data, and how to analyze and correct<\/p>\n\n\n\n
them; and<\/p>\n\n\n\n
3. Secure communication: including data encryption techniques, especially<\/p>\n\n\n\n
sharing of secret keys for encryption.<\/p>\n\n\n\n
Before we look into the nature and characterization of information in quan-<\/p>\n\n\n\n
tum systems, we need some terminology commonly used in this subject. The<\/p>\n\n\n\n
classic paradigm of information and communication is indicated in the cartoon<\/p>\n\n\n\n
in Figure 9.1.<\/p>\n\n\n\n
Two parties that may be in separate locations (we call them Alice and<\/p>\n\n\n\n
Bob after the tradition in communication theory) need to communicate some<\/p>\n\n\n\n
data. The term data refers to information converted into a form suitable for<\/p>\n\n\n\n
the physical protocol being used for transfer. Data is produced from informa-<\/p>\n\n\n\n
tion by a process called encoding. This process is essentially a mathematical<\/p>\n\n\n\n
function executed by a computing machine. At this stage, we are concerned<\/p>\n\n\n\n
with the quanti\ufb01cation of information present in the data, the e\ufb03ciency of<\/p>\n\n\n\n
encoding and how much the data can be compressed. If the security of the<\/p>\n\n\n\n
data is of importance, then this is the stage where secrecy is built into the<\/p>\n\n\n\n
message, a process called encryption.<\/p>\n\n\n\n
Alice, the sender, then transmits the encoded data by physical means<\/p>\n\n\n\n
known as the channel. At this stage, we are concerned about the e\ufb03ciency of<\/p>\n\n\n\n
177<\/p>\n\n\n\n
<\/p>\n\n\n\n
178 Introduction to Quantum Physics and Information Processing<\/p>\n\n\n\n
FIGURE 9.1: Communication of information<\/p>\n\n\n\n
the channel, quanti\ufb01ed by the rate at which data can be transmitted by the<\/p>\n\n\n\n
channel. Another important factor at this stage is noise. Data could get cor-<\/p>\n\n\n\n
rupted by various means and an error-correcting scheme like those we looked<\/p>\n\n\n\n
at in Chapter 10 has to be built into the communication protocol. If the data<\/p>\n\n\n\n
needs to be securely transmitted, then at this stage an eavesdropper (Eve)<\/p>\n\n\n\n
can tap into the channel and check how much it can be compromised.<\/p>\n\n\n\n
When the data reaches its destination with Bob, it needs to be decoded<\/p>\n\n\n\n
to be readable by Bob. This process is essentially the reverse of encoding,<\/p>\n\n\n\n
and the e\ufb03ciency of the whole protocol can be computed at this stage. The<\/p>\n\n\n\n
security of the protocol can also be checked if Alice and Bob now compare<\/p>\n\n\n\n
some of their data through other means.<\/p>\n\n\n\n
Quantum data processing can help us with making this process more e\ufb03-<\/p>\n\n\n\n
cient as well as more secure, as we will see in this chapter. The chief properties<\/p>\n\n\n\n
of quantum systems that will be exploited here are entanglement and the in-<\/p>\n\n\n\n
distinguishability of non-orthogonal states<\/p>\n","protected":false},"excerpt":{"rendered":"
The most successful practical applications of quantum mechanics in informa- tion theory have been in the \ufb01eld of communication. This is a very old \ufb01eld that has taken inputs from engineering, pure mathematics and computer science apart from physics. It is only natural that application of quantum techniques here should be among the \ufb01rst to […]<\/p>\n","protected":false},"author":1,"featured_media":4043,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[498],"tags":[],"class_list":["post-4103","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-information-and-communication"],"jetpack_featured_media_url":"https:\/\/workhouse.sweetdishy.com\/wp-content\/uploads\/2024\/09\/informative.png","_links":{"self":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4103","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/comments?post=4103"}],"version-history":[{"count":1,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4103\/revisions"}],"predecessor-version":[{"id":4104,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/posts\/4103\/revisions\/4104"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media\/4043"}],"wp:attachment":[{"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/media?parent=4103"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/categories?post=4103"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/workhouse.sweetdishy.com\/index.php\/wp-json\/wp\/v2\/tags?post=4103"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}