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mumpsimuspreviousAI and Robotics

Oct 25, 2013 (3 years and 10 months ago)

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A

quantum computer

is a device for

computation

that makes direct use of

quantum
mechanical

phenomena, such as

superposition

and entanglement, to perform
operations on

data.

Quantum mechanics
, also known as

quantum physics

or

quantum theory
, is a
branch of

physics

providing a mathematical description of much of the dual particle
-
like
and wave
-
like behavior and interactions of

ene
rgy

and

matter

Quantum superposition

is a fundamental principle of

quantum mechanics
. It holds that
a
physical system (say, an electron) exists in all its particular, theoretically
possible

states

(or, configuration of its properties) simultaneously;



The Turing machine, develop
ed by

Alan Turing

in the 1930s, is a theoretical device
that consists of tape of unlimited length that is divided into little squares. Each square
can either hold a symbol (1 or 0) or be left blank. A read
-
write device reads these
symbols and blanks, which

gives the machine its instructions to perform a certain
program. Does this sound familiar? Well, in a

quantum

Turing machine, the difference
is that the tape exists in a quantum state, as does the read
-
write head. This means that
the symbols on the tape c
an be either 0 or 1 or a

superposition

of 0 and 1; in other
words the symbols are both 0 and 1 (and all points in between) at the same time. While
a normal Turing machine can only perform one calculation at a time, a quantum Turing
machine can perform many

calculations at once.



In

quantum computing
, a

qubit

(

/
ˈ
k
ju
ː
b
ɪ
t
/
) or

quantum bit

is a unit of

quantum
information

the quantum analogue of the classical

bit

with
additional dimensions
associated to the

quantum properties

of a physical

atom
.


In 1965, Intel’s co
-
founder Go
rdon Moore saw that the number of transistors and the
speed of computer chips were doubling about every 18 months.

If technology followed Moore’s Law, then the shrinking size of circuitry packed into
silicon chips would eventually reach a point where indi
vidual elements would be no
larger than a few atoms.


Here, a problem arises because at the atomic scale of physical laws that govern the
behavior and properties of the circuit are inherently quantum in nature, not classical.
The limits of classical computers and its computations brought up the idea of compu
ters
based on quantum mechanics.

1970s and 1980s:

Theorists proposed idea of quantum computers.

1985:

Deutsh of Oxford University wrote paper on quantum computers that went
unnoticed. No one doubted quantum computer would work, but no point to this diffic
ult
and expensive task.


1994
, A computer scientist at AT&T Bell Labs suggested that the strange, almost
spooky way that a quantum computer could go about its business made it the
perfect
code
-
breaking machine
.

1996:

first quantum computer by IBM’s Chuang.

This computer and others to follow look
more like chemistry experiments than computers, but then, they are!

2001
:First working 7
-
qubit NMR computer demonstrated at IBM's Almaden Research
Center. First execution of Shor's algorithm. The number 15 was facto
red using 1018
identical molecules, each containing 7 atoms.

2009
: Researchers at

Yale University

created the first rudimentary solid
-
state quantum
processor. The two
-
qubit

superconducting chip was able to run elementary algorithms.
Each of the two artific
ial atoms (or qubits) were made up of a
billion

aluminum

atoms

but they acted like a single one that could occupy two different
energy states.

2011:

D
-
Wave Systems

announced the first commercial

quantum annealer on the
market by the name D
-
Wave One. The company claims this system uses a 128 qubit
processor chipset


During the same year in 2011 During the same year, researchers working at
the

University of Bristol

created an all
-
bulk optics system able to run an iterative version
of
Shor's algorithm
. They successfully managed to factorize 21.

D
-
Wave One, the technology uses a method called "quantum annealing"


to solve discrete
optimization problems. While that may sound obscure, it applies to all sorts of artificial
int
elligence
-
type applications such as natural language processing, computer vision,
bioinformatics, financial risk analysis, and other types of highly complex pattern matching.

While there is a substantial amount of exotic technology inside the D
-
Wave One, t
he system
has been built to require very little specialized knowledge to operate. Users interact with the
system via an API that allows the D
-
Wave One to be accessed remotely from a variety of
programming environments, including Python, Java, C++, SQL and
MATLAB



Shors:


The quantum computers power to perform calculations across a multitude of parallel universes
gives it the ability to quickly perform tasks that classical computers will never be able to
practically achieve. This power can only be unleashed with the correct

type of algorithm, a type
of algorithm that is extremely difficult to formulate. Some algorithms have already been
invented; they are proving to have huge implications on the world of cryptography. This is
because they enable the most commonly used crypto
graphy techniques to be broken in a matter
of seconds. Ironically, a spin off of quantum computing, quantum communication allows
information to be sent without eavesdroppers listening undetected.

We all use cryptography every day, and most of us do so with
out knowing it. If we rely
on it so much, is there any danger that the security of current cryptosystems could be
compromised? Certainly the consequences could be dire if all electronic commerce
were suddenly rendered insecure. Although still many years aw
ay, it turns out that there
is such a threat. Current cryptographic techniques are all based around advanced
mathematics, but the cryptography of the future is likely to pass to the realm of the
physicists.


Physicists have come up with the theoretical not
ion of a quantum computer which could
break virtually all known cryptographic algorithms. The properties of quantum physics
that allow particles to be in two states simultaneously can be harnessed to solve
problems in parallel with the same speed that coul
d be done if they were tackled
sequentially. It turns out that most of the mathematical problems that are at the heart of
our current cryptographic systems are perfectly suited to being tackled by quantum
computers. The power of quantum computers would lea
d to a new age of computing in
which previously intractable problems could be solved in an instant and will have a
revolutionary effect on all our lives.


Although quantum computers are still very much in their infancy, theorists have already
developed alg
orithms that could be run on a quantum computer if one were to exist.

The first, Shor's algorithm, can be adapted to crack virtually all existing public key
cryptographic algorithms that are considered to be secure today. Shor's algorithm would
allow a qua
ntum computer to solve factoring problems (used by the RSA algorithm), the
discrete logarithm problem (used by the El Gamal algorithm) and even certain versions
of the elliptic curve discrete logarithm problem (used in elliptic curve cryptography). A
secon
d algorithm known as Grover's algorithm provides a way for a quantum computer
to search an unsorted list, a method which could be used to crack symmetric ciphers.


Much effort is being expended into building a working Quantum computer, but it is likely to
be
many years before it becomes a reality. Although the advent of quantum computers would be
the nail in the coffin for many of the cryptographic algorithms in use today, there are other
algorithms and technologies ready to take their place. I believe we c
an look forward to an age
of quantum computers rather than needing to fear that they will make our computing insecure.