Quantum computing

Presented By:
Krishna M Patel - 120080116038
Priyanka G Patel - 120080116037

INDEX
 Computer Generation
 History
 Defination
 Why Quantum computing??
 introduction of Qubits
 How powerful are quantum computers
 Quantum algorithms
 Application
 Advantages and Disadvantages
 Present status
 Conclusion

 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

Year Scientist Research
1982 Feynman Idea of creating machines
based on the laws of
quantum mechanics
instead of the laws of
classical physics.
1985 David Deutsch Developed the quantum
turing machine, showing
that quantum circuits are
universal.
1994 Peter Shor A quantum algorithm to
factor very large numbers
in polynomial time.
1997 Lov Grover Develops a quantum search
algorithm with O(√N)
complexity
History:

 Quantum computing is the area of study focused on developing computer technology based on
the principles of quantum theory, which explains the nature and behaviour of energy and matter
on the quantum (atomic and subatomic) level.
 Quantum Computer:
 A quantum computer is a computation device that makes direct use of quantum-mechanical
phenomena, such as superposition and entanglement, to perform operations on data.

 By 2020 we will hit natural limits on the size of transistors
 Max out on the number of transistors per chip
 Reach the minimum size for transistors
 Reach the limit of speed for devices
 Eventually, all computing will be done using some sort of alternative structure
 DNA
 Cellular Automation
 Quantum

 In quantum computing, a qubit or quantum bit is a unit of quantum information.
 Qubits represent atoms, ions, photons or electrons and their respective control devices that are
working together to act as computer memory and a processor.
 A qubit is a two-state quantum-mechanical system.
 Vertical polarization
 Horizontal polarization
 A qubit has a quantum register.
 Similar to qubit, a qutrit, qudit is also used for other level quantum system.

 The two states in which a qubit may be measured are known as basis states.
 They are represented by Dirac notation.
 States are conventionally written as |0> and |1>:
 An excited state representing |1> and a ground state representing |0>.
 |ѱ>=α|0> + β|1>,
 When we measure this qubit in the standard basis, the probability of outcome for |0> is |α|2 and
outcome for |1> is |β|2.
 |α|2 + |β|2 = 1
 Operation on qubits:
 unitary transformation
 Standard basis measurement
Excited
State
Ground
State
Nucleus
Electro
nState
|0>
State
|1>

Bits:
 The device computes by
manipulating those bits with the
help of logical gates.
 A classical computer has a memory
made up of bits, where each bit holds
either a one or a zero.
Qubits:
 The device computes by
manipulating those bits with the
help of quantum logic gates.
 A qubits can hold a one,a zero or
crucially a superpositoion of these.

 A single qubit can be forced into a superposition of the two states denoted by the
addition of the state vectors:
 A qubit in superposition is in both of the states |1> and |0> at the same time.
 DEFINITION
 Two things can overlap each other without interfering with each other.In classical
computers,electrons cannot occupy the same space at the same time.

 Entanglement is the ability of quantum systems to exhibit correlation between
states within a superposition.
 Imagine two qubits,each in the state |0>+|1>(a superposition of 0 and 1).We can
entangle the two qubits such that the measurement of one qubit is always
correlated to the measurement of other qubit.

 Some of quantum algorithms can turn hard mathematical problems into easy
ones.
 The time takes to execute the algorithm must increase no faster than a
polynomial function of the size of the input.
 Potential use of quantum factoring for code-breaking purpose has raised the
suggestion of building a quantum computer.
 It may help in cryptography.

 A quantum algorithm is an algorithm which runs on a realistic model of quantum
computation.
 Quantum algorithm is a step-by-step procedure.
 ALGORITHM
I. Jozsa algorithm
II. Simon’s algorithm
III. Shor’s algorithm

 Jozsa algorithm:
 This algorithm solves a black-box problem which probably requires exponentially many
queries to the black box for any deterministic classical computer, but can be done with
exactly 1 query by quantum computer.
 Simon’s algorithm:
 This algorithm solves a black-box problem exponentially faster the any classical
algorithm, including bounded-error probabilistic algorithms.
 Shor’s algorithm:
 This algorithm solves the discrete logarithm problem and integer factorization
problem in polynomial time, whereas the best known classical algorithms take super-
polynomial time.

 Even though no quantum computer has been built that hasn’t stopped the
proliferation of papers on various aspects of the subject.Many such papers have
been written defining language specification.
 QCL –(Bernhard-omer)like C syntax and very compelet.
 qGCL –(Paolo Zuliani and others)
 Quantum C-(Stephen Blaha)Currently just a specification.

 Quantum computer can be used in cryptography.
 Modelling and indexing of very large databases.
 It can be used to solving complex mathematical problems.
 Military searches of quantum computer.
 Google image search.
 Teleportation
 Improved error correction and error detection.

 Quantum cryptography describes the use of quantum mechanical effects to
perform cryptographic tasks or to break cryptographic systems.
 Well-known examples of quantum cryptography are the use of quantum
communication to exchange a key securely and the hypothetical use of quantum
computers that would allow the breaking of various popular public-key
encryption and signature schemes.
 The advantage of quantum cryptography lies in the fact that it allows the
completion of various cryptographic tasks that are proven or conjectured to be
impossible using only classical.
 The most well known and developed application of quantum cryptography
is quantum key distribution (QKD).

Advantages Disadvantages
Increase in computing power Although qubit can hold many possible
values but only one classical result can be
obtained from every run.
Advance in security Repeated runs may be necessary to obtain
the desired result.
Teleportation It is impossible to copy qubits(no-cloning
theorem).
Advantages and Disadvantage of Quantum computing

 Quantum physicists from the university of Innsbruck have set another world
record: They have achieved controlled entanglement of 14 quantum bits and, thus
realized the largest quantum register that has ever been produced.
 Researchers at delft University of technology have succeeded in carrying out
calculations with two qubits.
 December 19, 2001-IBM performs shor’s algorithm.

 It discusses the inevitability of quantum computers, how they originated, and
what is different about them from classical computers
 It is is intended to be accessible to the general people, so it will explain the basics
of a few quantum computer features at the risk of over-simplification
 Quantum computes are coming, and they will require a new way of looking at
computing
 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).
 Desktop quantum computers expected by many within 10 years.

Quantum computing

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