4. Quantum computing
Theoretical study of
quantum systems
Those systems are
applied to make a
quantum computer
Uses “QUBITS”
5. Bits (classical computing)
A bit can exist only in one
state
Either 0 or 1
Information behaviour : one
single direction
Logic gates are irreversible
6. Qubits
Can exist as 0 or 1 or
coherent superposition of
both
Operation on a qubit
effectively acts on both
values at a same time
An exist in both values
simultaneously
10. Physical interpretation
Light pulse of frequency for
time interval t/2
State |0> State |0> + |1>
11. Representation of Data -
Superposition
A single qubit can be forced into a superposition
of the two states denoted by the addition of the
state vectors:
|> = |0> + |1>
Where and are complex numbers and | |
+ | | =1
12. Processors
Classical processors Quantum processors
Each processor perform Single processor can
one computation,while perform multiple
other processors do computations on its own
other computations simultaneously
13. As increase in no.of Qubits
Increase in quantum parallelism
Solve
Quantum parallelism problems in
+ fraction of
Algorithm time
15. Reversible operations
For a computer to run fast
Inputs can be correctly deduced from
outputs
Irreversible computation involve loss of
information
17. Quantum Gates - Hadamard
Simplest gate involves one qubit and is called a Hadamard
Gate (also known as a square-root of NOT gate.) Used to put
qubits into superposition.
H H
State State State
|0> |0> + |1>
|1>
Note: Two Hadamard gates used in
succession can be used as a NOT gate
18. Quantum computer
Use direct use of quantum mechanical
phenomena
Utilizes quantum properties to represent data
Could solve certain problems much faster
19. Shor’s algorithm
Allows extremely quick factoring
To factor a 1000 digit number
For a classical computer it take 10
million billion years
For a quantum computer its just 20 min
20. Building a quantum computer
It can’t be from transistor and diodes
A new type of technology is needed
A technology that enables qubits to exist
as coherent superposition of 0 and 1
23. References
Text books: 1. Palanisamy
2. A quantum revolution for computing. Julian
Brown, New Scientist 24/9/94
Wikipedia.org
Videos on quantum computation by
“centre for quantum computation and
communication technology”