| Mirror
Magazine |
||||
|
Techno
Page - By Harendra Alwis You are all
welcome to write in with your views and comments to technopage_lk@yahoo.com What is
Quantum Computing? A BIT is a
fundamental unit of information, classically represented as 0 or
1 in a digital computer. Each BIT is physically realized through
a macroscopic physical system, such as the magnetization on a hard
disk or the voltage output of a transistor. A document, for example,
comprising N (number of) characters stored on the hard drive of
a typical computer is described by a string of 8 x N 0s and 1s.
(A character is represented by 8 Bits). Herein lies a key difference
between the classical computer and a quantum computer. Where a classical
computer obeys the familiar laws of classical physics, a quantum
computer is a device that harnesses concepts and laws of quantum
mechanics that give a novel and radical way of processing information. In a quantum
computer, the fundamental unit of information (called a quantum
bit or 'qubit'), is not binary but rather more quaternary in nature.
This qubit property is a direct consequence of the laws of quantum
mechanics which differ radically from the laws of classical physics.
A qubit can
exist not only in a state corresponding to the logical state 0 or
1 as in a classical Bit, but also in states corresponding to a mixture
or superposition of these classical states. In other words,
a qubit can exist as 0, 1 or simultaneously as both 0 and 1, with
a numerical coefficient representing the probability for each state. This may seem
absurd because everyday phenomena are governed by classical physics,
not quantum mechanics which override Newtonian Physics at the atomic
level. Thus, a quantum
computer working on a qubit can make calculations using both values
0 and 1 simultaneously. A qubyte, being
made up of 8 qubits, can be all values from 0 to 255 simultaneously!
Extending this concept to multi-qubyte systems, it can be seen that
there is potential for computational efficiency exponentially beyond
anything possible with classical computers. Here's
a cookie for you Following the
feature on cookies and the potential threat that unsecured cookies
pose to Internet security, I received many questions regarding what
cookies are, and how they work. So let me explain. Cookies are
text files that store messages that a Web server transmits to a
Web browser so that the Web server can keep track of the user's
activity on a specific Web site. The message that the Web server
conveys to the browser is in the form of an HTTP header that consists
of a text string. The browser in turn stores the cookie information
on the hard drive so when the browser is closed and reopened at
a later date the cookie information is still available. Web sites use
cookies for several different reasons: * To collect
demographic information about who is visiting the Web site. Sites
often use this information to track how often visitors come to the
site and how long they remain on the site. * To personalize
the user's experience on the Web site. Cookies can help store personal
information about you so that when you return to the site you have
a more personalized experience. If you have ever returned to a site
and have seen your name mysteriously appear on the screen, it is
because on a previous visit you gave your name to the site and it
was stored in a cookie so that when you returned you would be greeted
with a personal message. A good example of this is the way some
online shopping sites will make recommendations to you based on
previous purchases. The server keeps track of what you purchase
and what items you search for and stores that information in cookies. * To monitor
advertisements. Web sites will often use cookies to keep track of
what ads it lets you see and how often you see ads. Cookies do
not act maliciously on computer systems. They are merely text files
that can be deleted at any time - they are not plug-ins nor are
they programs. Cookies cannot be used to spread viruses and they
cannot access your hard drive. This does not mean that cookies are
not relevant to a user's privacy and anonymity on the Internet.
Cookies cannot read your hard drive to find out information about
you; however, any personal information that you give to a Web site,
including credit card information, will most likely be stored in
a cookie unless you have turned off the cookie feature in your browser.
In only this way are cookies a threat to privacy. The cookie will
only contain information that you freely provide to a Web site. Cookies have
six parameters that can be passed to them: 1. The name
of the cookie. 2. The value
of the cookie. 3. The expiration
date of the cookie - this determines how long the cookie will remain
active in your browser. 4. The path
the cookie is valid for - this sets the URL path the cookie is valid
in. Web pages outside that path cannot use the cookie. 5. The domain
the cookie is valid for - this takes the path parameter one step
further. This makes the cookie accessible to pages on any of the
servers when a site uses multiple servers in a domain. 6. The need
for a secure connection - this indicates that the cookie can only
be used under a secure server condition, such as a site using SSL. Both Netscape
and Microsoft Internet Explorer (IE) can be set to reject cookies
if the user prefers to use the Internet without enabling cookies
to be stored. In Netscape, follow the Edit/Preferences/Advanced
menu and in IE, follow the Tools/Internet Options/Security menu
to set cookie preferences. Creating a platform |
||||
Copyright © 2001 Wijeya Newspapers
Ltd. All rights reserved. |
