Quantum computers

QUANTUM COMPUTERS

Presented BY

1) OMKAR AGRAWAL 3) YASH GANGANI

5) Abhishek SHARMA 2) PRATIK SINGH 4) NILESH DAVE

ABOUTScientists have already built basic quantum computers that can perform certain calculations; but a practical quantum computer is still years away. In this presentation, you'll learn what a quantum computer is and just what it'll be used for in the next era of computing.

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HISTORY

Quantum computing was first theorized less than 30 years ago, by a physicist at the Argonne National Laboratory. Paul Benioff is credited with first applying quantum theory to computers in 1981. Benioff theorized about creating a quantum Turing machine. Most digital computers, like the one we are using to present this ppt, are based on the Turing Theory.

Qc’s genera l desc r ip t ion and work ing .

A QCs' taps directly into the fundamental fabric of reality – the strange and counterintuitive world of quantum mechanics – to speed

computation.

They make direct use of quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data.

Large-scale QCs's would theoretically be able to solve certain problems much more quickly than any classical computers that

use even the best currently known algorithms, like integer factorization using

Shor's - algorithm , and others.

Classical Bit s vs Quantum bits(Qubits)• In a classical system, a bit would have to be

in one state or the other thought of as 0 and 1.

o The difference is that whereas the state of a bit is either 0 or 1, the state of a qubit can also be a superposition of both. It is possible to fully encode one bit in one qubit. However, a qubit can hold even more information, e.g. up to two bits using super dense coding.

An important distinguishing feature between a qubit and a classical bit is that multiple qubits can exhibit quantum entanglement.

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 can 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.

Entanglement also allows multiple states (such as the Bell state) to be acted on

simultaneously, unlike classical bits that can only have one value at a time.

• Today's computers, like a Turing machine, work by manipulating bits that exist in

one of two states: a 0 or a 1. QCs's aren't limited to two states; they encode

information as quantum bits, or qubits, which can exist in superposition. Qubits

represent atoms, ions, photons or electrons and their respective control

devices that are working together to act as computer memory and a processor.

Because a QC can contain these multiple states simultaneously, it has the potential to be millions of times more powerful than

today's most powerful supercomputers.

• According to physicist David Deutsch, this parallelism allows a QC to work on a million computations at once, while your desktop PC works on one.

• The most advanced QCs's have not gone beyond manipulating more than 16 qubits, meaning that they are a far cry from practical application.

Current predicaments with QCs’.

I. One of the problem with the idea of QCs is that if you try to look at the

subatomic particles, you could bump them, and thereby change

their value. If you look at a qubit in superposition to determine its

value, the qubit will assume the value of either 0 or 1, but not both (effectively turning your spiffy QC into a mundane digital computer).

II.  To make a practical QC, scientists have to devise ways of making measurements

indirectly to preserve the system's integrity. Entanglement provides a

potential answer. In quantum physics, if you apply an outside force to two atoms, it can cause them to become entangled, and

the second atom can take on the properties of the first atom. So if left

alone, an atom will spin in all directions. The instant it is disturbed it chooses one spin, or one value; and at the same time, the second entangled atom will choose an

opposite spin, or value. This allows scientists to know the value of the qubits

without actually looking at them.

Will Quantum Computers Replace Classical Computers .

• I highly doubt QCS’ will ever be add-ons. QCS’ require a low operating temperature. Close to absolute zero temps actually. No way a cooling apparatus of that magnitude would ever fit in a case much less a gpu size card.

• Studying quantum information illuminates the basic concepts of quantum mechanics better than anything else. And, one day, this could become the standard way of learning quantum mechanics.

Quantum Computing PowerInteger Factorization.

Impossible for digital computers to factor large numbers which are the products of two primes of nearly equal size

QC with 2n qubits can factor numbers with lengths of n bits (binary)

Quantum Database Search.Example: To search the entire Library of

Congress for one’s name given an unsorted database...Classical Computer – 100 yearsQuantum Computer – ½ second

• We know that QCs’ will be faster for many computational tasks, from modelling nature to searching large amounts of data. I think there are many more applications and, perhaps, the most important ones are still waiting to be discovered.

Researches done using:

Researches done on:

1) Https://www.google.co.in

2) https://www.scholar.google.com

3) duckduckgo.com

1) http://www.wikipedia.org

2) https://www.researchgate.net/

3) http://computer.howstuffworks.com/

4) Various sites that do not have a real domain name or IP address.

Herby we end our presentation with a summary of points.

QCs’ still are more of theory than practical. They operate on Quantum information laws . They work on qubits rather than classical bits. Quantum entanglements and superposition. Current advantages of QCs’. Current predicaments with QCs’. Qcs’ in near future.