The document provides a comprehensive overview of quantum computers, detailing their operation based on quantum physics through qubits, and distinct features such as superposition and entanglement. It discusses their advantages over classical computers, potential applications in fields like cryptography and medicine, as well as their shortcomings and issues related to dependency on technology. Lastly, it includes references for further exploration of quantum information processing and existing quantum computing platforms.

1. QUANTUM COMPUTER
Kumar Abhijeet
Regd. no. : 1401209282
ECE “A” ,Grp-2
Roll -25

2. CONTENTS :
• What is Quantum computer
• Why Quantum computer
• Everything about qubit.
• Type of Quantum processor
• Quantum gates
• Architecture of Quantum computer
• Algorithms based on Quantum computer
• Applications
• Shortcomings
• Conclusion
• References

3. Quantum computer :
• A quantum computer is a machine that performs calculations
based on quantum physics.
• Built around “qubits” rather than “bits”.
• Operation in an extreme environment :
– 150 X colder than interstellar space
– Shielded to 50,000 X less than Earth’s magnetic field
– very low pressure : 10B times lower than
atmospheric pressure .

4. Quantum properties used:
• Superposition
– An state exists in all the possible configurations of the configuration
space.
• Entanglement
– There is a relationship among the features of the entangled elements.
• Uncertainty principle
– Every time a measure on the system is made, the system is changed by
that measure.
• Tunnelling
– Through tunnelling a electron or photon particle can travel or teleport
itself to any location in 0 time duration.
• Decoherence
– In a coherent state made up of several elements, all the quantum
features are live and the system appear as one quantum system.
Decoherence gives back individual identity to each system component.

5. Why quantum computer :
• In future transistors will be so small and it will generate so much
heat that standard silicon technology may eventually collapse.
• If scale becomes too small, Electrons tunnel through micro-thin
barriers between wires corrupting signals.
• Process massive amount of complex data in very less time than
classical computer .
• Ability to solve scientific and commercial problems, which never
have even solved.
• Process data in a much faster speed.
• Capability to convey more accurate answers.

6. Everything about the qubit :
• Qubit, just like ‘classical bit‘, is a memory element, but can hold
not only the states |0 and |1 but also linear superposition of
both states, α1|0+α2|1.
• This superposition makes Quantum Computing fundamentally
different.
• This sphere is often called the Bloch sphere, and it provides a
useful means to visualize the state of a single qubit.

7. Qubit: How It Works
• 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>.
• A qubit in superposition is in both of the
states |1> and |0> at the same time.
Excited
State
Nucleus
Light pulse of
frequency  for
time interval t
Electron
State |0> State |1>
Ground
State
State |0> + |1>

8. Classical bit Vs. Qubit
i >Data unit of classical computing
ii>Its measurement is deterministic
i>Data unit of quantum computing.
ii>Its Measurement is stochastic.

9. Types of Quantum Processors :
• Spin Qubits – Electron or nuclear spins on a solid
Substract.
• Superconducting Circuits – currents superposition around a
superconductor.
• Photonic Circuits – The qubits are photons driven in
silicon circuits.

10. Quantum Gates :
• Hadamard Gate:
– transforms |0 to (|0 +|1)/2 and |1 to (|0 -|1)/2
• Pauli-X gate:
– Quantum equivalent of NOT gate.
– Transforms |1 to |0 and |0 to |1
• Pauli-Y gate:
– Transforms |1 to -i|0 and |0 to i|1
• Pauli-Z gate:
– Transforms |1 to -|1 and |0 remains unchanged.
• Phase shift gate:
– Transforms |1 to ei |1 and |0 remains unchanged.
– Modifies(rotates) the phase of quantum state by .

11. Architecture of Quantum computer :
• Most important parts of Quantum computer :
– Dilution Refrigerator
– QPU(Quantum Processing Unit)
Inside the computer

12. Dilution Refrigerator:
• It maintain the temperature inside the
box at 15mK (-273.135⁰C) .
• Uses liquid helium refrigerant in a
closed-loop system .
• Reduce the temperature stepwise
manner.

13. QPU(Quantum Processing Unit):
• built from a lattice of tiny loops of the metal niobium, each of
which is one qubit (shown in red).
• Below temperatures of 9.2 kelvin, niobium becomes a
superconductor and exhibits quantum mechanical effects .
• When in a quantum state, current flows in both directions
simultaneously, which means that the qubit is in superposition.
• At the end of the problem-solving
process, this superposition collapses
into one of the two classical states,
0 or 1.

14. Quantum Algorithm:
• Shor Algorithm
– Number of steps that a classic computer needs to run in order to
find the prime factors of a number N of x digits.
It grows exponencially with x
937 x 947 = N (easy)
887339 = p x q (hard)

15. • Grover Algorithm :
– How many attempts need a data search in an unordered N-
element database to locate a particular element?
An average of N/2 attemps are needed
An quantum computing executing the Grover’s
algorithm would run √N attempts.

16. Applications of Quantum computer:
• Cryptography :
– Quantum computers have the potential to keep private data safe
from snoops and hackers, no matter where it is stored or
processed.
• Medicine & Materials :
– A quantum computer mimics the computing style of nature,
allowing it to simulate, understand and improve upon natural
things—like molecules, and their interactions.
• Machine Learning :
– Research indicates that quantum computing could significantly
accelerate machine learning and data analysis tasks.
• Searching Big Data :
– Quantum computing can search the ever-growing amount of data
being created, and locate connections within it, significantly faster
than classical computers, that will have tremendous impact across
many industries.

17. Disadvantages and Problems:
• Moral, ethical, social, and economic issues:
– Growing too much dependency on machines.
– Economic division: who can/cannot afford technology.
• Not suitable for word processing and email.
• Problem of Decoherence, the need of a noise free environment.
• Complex hardware schemes like superconductors.

18. Quantum Experience :
• The D-Wave 2000Q system provides a standard Internet API, with
client libraries available for C/C++, Python, and MATLAB.
• IBM provides a web based application to access Real Quantum
Processor which is currently working on the IBM Quantum
computing lab and a simulator to setup your own topology.
https://quantumexperience.ng.bluemix.net/qx/editor

19. Conclusion :
• Quantum computer has more to offer.
• Advantages outweighs disadvantages.
• Wide range of applications.
“My students don’t understand Quantum Mechanics, because I don’t
understand it. Nobody understand Quantum Mechanics.”
Richard Feynman

20. References :
[1] Neil Gershenfeld and Isaac L. Chuang, “Quantum lock”, “Quantum Computing
with Molecules”, pg no – 2 , http://cba.mit.edu/docs/papers/98.06.sciqc.pdf ,
Year- 1998
[2] Pijush Kanti Bhattacharjee, “Quantum Information Processing” “Digital
Combinational Circuits Design By QCA Gates “, pg -5 , 1, February, 2010
[3] John Preskill, “Classical and quantum circuits”, “Quantum Information ”,
Chapter 5 ,pg -27, http://www.theory.caltech.edu/~preskill/ph219/chap5_15.pdf,
(July 2015)
[4] J.M.Chow, “Experimental one-way quantum computing”,”Quantum computer”,
https://www.nature.com/nature/journal/v460/n7252/pdf/nature08121.pdf,
Nature 460, 240-244 (9 July 2009)
[5] D-wave journal , pg no – 6 ,
https://www.dwavesys.com/sites/default/files/DWave%202000Q%20Tech%20Coll
ateral_0117F.pdf

21. THANK YOU !

22. ANY QUESTIONS ?