After Moore’s law-which states that the number of microprocessors/transistors on an integrated circuit doubles once every two years at the same cost—is running out of steam. The question is what might replace it Gordon Moore’s Law benefits for some degree of expansion. Already larger smartphones and tablets and improvements in hardware efficiency are picking up some of the slack as it becomes harder and harder to fit more transistors on a dense integrated circuit. So the Moore’s Law must come to an end because it is a physical phenomenon governed by the physical limits of the universe. To solve for the future we need to design a new type of computer which, aptly named “Quantum computers”, utilizes the laws of quantum mechanics to create exponentially greater processing power and uses a new unit of information called a “ Qubit ”, rather than a bit. Scientists 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 for what it’ll be used in the next era of computing.

1. QUANTUM COMPUTERS
By
S.Lakshmi Teja

2. CONTENTS
• Classical Computers – Evolution & Moore’s Law
• Quantum Computers
-Data Representation
-Qubit
-Quantum Properties : Superposition,Decoherence,Entanglement
-Advantages and Disadvantages
• Conclusion

3. CLASSICAL COMPUTERS
• How Computers Work??
A classical computer has a memory made up of bits, where each bit is
represented by either a one or a zero.
Computers function by storing data in a binary number format, which result
in a series of 1’s & 0’s retained in electronic components such as transistors.

4. EVOLUTION OF CLASSICAL COMPUTERS
• First generation(1939-’54)-Vacuum tubes
• Second generation(1954-’59)-Transistors
• Third generation(1959-’71)- IC (Integrated Circuit based)
• Fourth generation(1971-’91)- Microprocessor (VLSI)
• Fifth generation(1991 & beyond)- Microprocessor (ULSI)

5. MOORE’S LAW
• Gordon Moore, Intel Co-founder said that the number of transistors economically
crammed into a single computer chip was doubling every two years.

6. CLASSICAL COMPUTERS
• Accurate and speedy computation machine
• Any complex computation or logical work like laboratory work become easy
• Some kinds of numerical problems cannot be solved using conventional computers.
Example: Factorization of a large number (say 500 digit number)

7. QUANTUM COMPUTERS
• Quantum computers are different from digital electronic computers based
on transistors. Whereas digital computers require data to be encoded into binary
digits (bits), each of which is always in one of two definite states (0 or 1), quantum
computation uses quantum bits (qubits), which can be in superpositions of states.

8. DATA REPRESENTATION
• Quantum Bit(Qubit) is used.
• 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.

9. QUBIT
• A quantum bit or qubit is a unit of quantum information.
• Many different physical objects can be used as qubits such as atoms, photons, or
electrons.
• Exists as a ‘0’, a ‘1’ or simultaneously as a superposition of both ‘0’ & ‘1’

10. PHYSICALREPRESENTATIONOFQUBITS
• A single atom that is in either Ground or Excited state.
• Ground state representing |0 .
• Excited state representing |1 .

11. PHYSICALREPRESENTATIONOFQUBITS

12. MORE ABOUT QUBITS
• Qubit in superposed state occupies all the states between |0 and |1
simultaneously , but collapses into |0 or |1 when observed physically.
• A qubit can thus encode an infinite amount of information.

13. QUBITS IN SUPERPOSED STATE

14. QUANTUM PROPERTIES
• Superposition
• Decoherence
• Entanglement

15. SUPERPOSITION
• Property to exist in multiple states.
• In a quantum system, if a particle can be in states |A and |B, then it can also be in
the state 1|A + 2|B ; 1 and 2 are complex numbers.

16. 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.

17. DECOHERENCE
• The influence of external environment causes the states in the computer to change
in a way that is completely unintended and is unpredictable, rendering the
computer useless.
• This is called decoherence.
• The biggest problem.
• So quantum computer to work with superposed states, it has to be completely
isolated from the rest of the universe (not observing the state, not measuring it, ...)

18. 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.

20. ENTANGLEMENT
• Most important property in quantum information.
• States that two or more particles can be linked, and if linked, can change properties
of particle(s) changing the linked one.
• Two particles can be linked and changed each other without interaction.

21. WHAT CAN A QUANTUM COMPUTER DO THAT A
CLASSICAL COMPUTER CAN’T?
• Factoring large numbers.
Multiplying two large numbers is easy for any computer. But calculating
the factors of a very large (say, 500-digit) number, on the other hand, is
considered impossible for any classical computer.

22. BUT WE DON’T WANT TO FACTOR VERY LARGE
NUMBERS…
• Nobody wants to factor very large numbers! That’s because it’s so difficult – even
for the best computers in the world today. In fact, the difficulty of factoring big
numbers is the basis for much of our present day cryptography.
Eg: The method used to encrypt your credit card number when you’re
shopping online, relies completely on the factoring problem. The website you
want to purchase from gives you a large "public" key (which anyone can
access) to encode your credit card information.This key actually is the product
of two very large prime numbers, known only to the seller. The only way
anyone could intercept your information is to know those two prime numbers
that multiply to create the key.

23. RESEARCHES GOING ON

24. GOOGLE’S QUANTUM COMPUTER
• GOOGLE is upgrading its quantum computer. Known as the D-Wave, Google’s machine is
making the leap from 512 qubits—the fundamental building block of a quantum
computer—to more than a 1000 qubits.
• Each qubit, D-Wave says, is a superconducting circuit—a tiny loop of flowing current—and
these circuits are dropped to extremely low temperatures so that the current flows in both
directions at once. The machine then performs calculations using algorithms.
• D-Wave says that most of the power needed to run the system is related to
the extreme cooling. The entire system consumes about 15 kilowatts of
power, while the quantum chip itself uses a fraction of a microwatt.

25. GOOGLE’S QUANTUM COMPUTER

26. ADVANTAGES
• Could process massive amount of complex data.
• Ability to solve scientific and commercial problems.
• Process data in a much faster speed.
• Capability to convey more accurate answers.

27. DISADVANTAGES AND PROBLEMS
Security and Privacy Issues:
• Ability to crack down password (s).
• Capability to break every level of encryption.
• Problem of Decoherence, the need of a noise free environment.
• Complex hardware.
• Lots of heat
• Expensive
• Difficult to build

28. CONCLUSION
• Simulation of quantum systems will allow us to study, in remarkable detail,
the interactions between atoms and molecules. This could help us design
new drugs and new materials.
• Researchers are constantly working on new quantum algorithms
and applications. But the true potential of quantum computers likely hasn’t
even been imagined yet. The inventors of the laser surely didn’t envision
supermarket checkout scanners and eye surgery. Similarly, the future uses
of quantum computers are bound only by imagination.
• Quantum computers could one day replace silicon chips, just like the
transistor once replaced the vacuum tube.

29. THANK YOU