Quantum computation - Introduction

Quantum Computation
A New Era of Future Computing
Aakash Martand
Marwar Engineering College & Research Centre, Jodhpur
Department of Computer Science, VIII Sem.

2
Introduction
History of Computation
Computing Generations
Moore’s Law
Classical Computing & Challenges
What is Quantum Computing
Applications & Advantages
Challenges
Present & Future Prospects
Conclusions
OVERVIEW

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Computation
Computation
A process following a well-defined model that is understood and can be
expressed in an algorithm, protocol, network topology, etc.
In a general way, we can define computing to mean any goal-oriented activity
requiring, benefiting from, or creating computers. Thus, computing includes designing
and building hardware and software systems for a wide range of purposes; processing,
structuring, and managing various kinds of information; doing scientific studies using
computers; making computer systems behave intelligently; creating and using
communications and entertainment media; finding and gathering information relevant to
any particular purpose, and so on. The list is virtually endless, and the possibilities are
vast.

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History of Computation
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Pascaline – 1642
Step Reckoner – 1672
Blaise Pascal invented the mechanical
calculator in 1642. First called the Arithmetic
Machine, Pascal's Calculator and
later Pascaline, this calculating machine could add
and subtract two numbers directly and multiply
and divide by repetition.
The Step Reckoner (or Stepped
Reckoner) was a digital mechanical
calculator invented by German
mathematician Gottfried Wilhelm
Leibniz around 1672

7
Difference Engine – 1822
A Difference Engine is an
automatic mechanical calculator designed to
tabulate polynomial functions.
J. H. Müller, an engineer, conceived
of the idea of a difference machine in 1786,
but Müller was unable to obtain funding to
progress with the idea.
On June 14, 1822, Charles
Babbage proposed the use of such a machine.
This machine used the decimal number system
and was powered by cranking a handle.

88
ENIAC - 1946
ENIAC (Electronic Numerical
Integrator And Computer) was the first electronic
general-purpose computer. It was Turing-complete,
digital, and capable of being reprogrammed to solve a
large class of numerical problems.
When ENIAC was announced in 1946 it
was heralded in the press as a "Giant Brain". It had a
speed of one thousand times that of electro-
mechanical machines.
Finished shortly after the end of WWII,
one of its first programs was a study of the feasibility
of the hydrogen bomb.
ENIAC contained 17,468 vacuum tubes,
7,200 crystal diodes, 1,500 relays, 70,000 resistors,
10,000 capacitors and around 5 million hand-
soldered joints. It weighed more than 30 short tons (27
t), was roughly 8 by 3 by 100 feet (2.4 m × 0.9 m ×
30 m), took up 1800 square feet (167 m2), and
consumed 150 kW of power. This led to the rumor
that whenever the computer was switched on, lights in
Philadelphia dimmed.

9
Vacuum Tubes

1010
Texas Instruments 1954 Transistor
A replica of the first working transistor.

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Computing Generations
• First Generation (1940-1956)
– Vacuum Tubes
• Second Generation (1956-1963)
– Transistors
• Third Generation (1964-1971)
– Integrated Circuits
• Fourth Generation (1971-Present)
– Microprocessors
• Fifth Generation (Present and Beyond)
– Artificial Intelligence

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Gordon Earle MooreGordon Earle Moore is an
American businessman and co-
founder and Chairman of Intel
Corporation and the author of Moore's
Law.
Moore's law is the
observation that the number
of transistors on integrated
circuits doubles approximately every
two years. Gordon E. Moore
described the trend in his 1965
paper. His prediction has proven to be
accurate, in part because the law is
now used in the semiconductor
industry to guide long-term planning
and to set targets for research and
development.
Moore’s Law

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Intel 10 Core Xeon Westmere-EX
Intel’s 10 Core
Xeon Westmere-EX
Processor with 32nm
thickness transistors.
It is 3000 times
thinner than human
hair…!!
Surprisingly, Intel
is working on 22nm
processor & will be
available soon

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• Accurate and speedy computation machine
• Part of life because logical work can also be done
• Many kinds of numerical problems cannot be solved using conventional
computers.
• Example: Factorization of a number
• The computer time required to factor an integer containing N digits is
believed to increase exponentially with N.
• Advantages
– Makes work easy and faster
– Any complex computation or logical work like laboratory work become easy
Classical Computers
Classical Computing

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Classical Computing
Challenges With Classical Computing:
• By 2020 to 2025, transistors will be so small and it will
generate so much heat that standard silicon technology may
eventually collapse.
Already Intel has implemented 32nm silicon technology
• If scale becomes too small, Electrons tunnel through micro-
thin barriers between wires corrupting signals.

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A Quantum Computer is a machine that performs
calculations based on the laws of quantum mechanics
which is behavior of particles at subatomic level.
A Quantum is a smallest possible discrete unit of any
physical property
Quantum Computing

23
Quantum Computing
As in classical computers transistors are used which may be
in ON or OFF state i.e. either ‘1’ or ‘0’ which are classical bits used
for computing, process data, store data etc. The whole classical
computing is based on just ‘0’ or ‘1’.
In Quantum Computing, Quantum bits are used which have
some special properties. A Quantum bit or ‘Qubit’ is a unit of
quantum information which may be ‘1’ or ‘0’ or ‘Both’ at a same
time.
Many different physical objects can be used as qubits such as
atoms, photons, or electrons.

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Quantum Computing
This sphere is
often called the
Bloch sphere, and it
provides a useful
means to visualize
the state of a single
qubit.
Qubit

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• A physical implementation of a qubit could use the
two energy levels of an atom. An excited state
representing |1> and a ground state representing
|0>.
Excited
State
Nucleus
Light pulse of
frequency  for
time interval t
Electron
State |0> State |1>
Ground
State
Quantum Computing

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Quantum Computing
Quantum Computers use quantum mechanical
phenomena-
• Superposition
• Entanglement

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Quantum Computing
Quantum Superposition
•An electron has dual nature.
•It can exhibit as a particle and also as wave.
•Wave exhibits a phenomenon known as superposition of
waves.
•This phenomena allows the addition of waves numerically.
•One example of a two-state quantum system is the polarization of a
single photon

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A single qubit can be forced into a superposition of the two states denoted
by the addition of the state vectors:
|> = 1 |0> + 2 |1>
Where 1 and 2 are complex numbers and |1| + |2 | = 1
Quantum Computing
Light pulse of
frequency  for time
interval t/2
State |0> State |0> + |1>
2 2

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Quantum Computing
Quantum Entanglement
In Quantum Mechanics, it sometimes occurs that a
measurement of one particle will effect the state of another
particle, even though classically there is no direct
interaction.
When this happens, the state of the two particles is
said to be entangled.

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Applications & Advantages
Speed & Accuracy

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Parallel Processing

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It is the method in which a quantum computer is able
to perform two or more computations simultaneously.
In classical computers, parallel computing is
performed by having several processors linked
together.
In a quantum computer, a single quantum processor is
able to perform multiple computations on its own.

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• Parallelism allows a quantum computer to work on many
computation at once.

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Encryption

67
Challenges
 Number of bits in a word.
◦ 12-qubit machines is the most advanced to
date.
◦ Difficulty with large words is, too much
quantum interaction can produce undesired
results. Since all the atoms interact with
each other.
 Physical size of the machines.
◦ Current machines are too large to be of
practical use to everyday society.

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Present & Future Prospects
• When processor components reach atomic scale,
Moore’s Law breaks down
– Quantum effects become important whether we want
them or not
But huge obstacles in building a practical
quantum computer!

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Present & Future Prospects
Quantum physicists from the University of Innsbruck have
set another world record: They have achieved controlled
entanglement of 14 quantum bits (qubits) and, thus, realized the
largest quantum register that has ever been produced.
If large-scale quantum computers can be built, they will be
able to solve certain problems much faster than any classical
computer using the best currently known algorithms (for
example integer factorization using Shor's algorithm or
the simulation of quantum many-body systems).

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Conclusion
• Quantum Computing could provide a radical change in
the way computation is performed.
• The advantages of Quantum Computing lie in the
aspects of Quantum Mechanics that are peculiar to it,
most notably entanglement.
• Classical Computers will be significantly larger than
Quantum Computers for the foreseeable future.

Quantum computation - Introduction

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