QUANTUM INFORMATIONTECHNOLOGY

PREPARED BY:FENNY

THAKRAR

DEFINITION

Quantum information theory is the study of how to integrate information theory with quantum mechanics, by studying how information can be stored with (and retrieved from) a quantum mechanical system.

QUANTUM INFORMATION TECHNOLOGY IS NOTHING BUT DEALING WITH COMPUTERS USING QUANTUM PHYSICS…

AND HENCE ITS ALSO CALLED QUANTUM COMPUTING…

WHAT IS QUANTUM COMPUTATION?

Computation with coherent atomic-scale dynamics.

The behavior of a quantum computer is governed by the laws of quantum mechanics.

THE POWER OF QUANTUM COMPUTATION…

In quantum systems possibilities count, even if they never happen! -like particle theory.

Each of exponentially many possibilities can be used to perform a part of a computation at the same time.

WHY BOTHER ABOUT QUANTUM COMPUTATION???

Moore’s Law: We hit the quantum level

2010~2020. Quantum computation is more

powerful than classical computation.

More can be computed in less time—the complexity classes are different!

QUBIT Digital systems have – bit Quantum systems have – qubit The primary piece of information in

quantum information theory is the qubit, an analog to the bit (1 or 0) in classical information theory.

The two position states of a photon in a Mach-Zehnder apparatus is just one example of a quantum bit or qubit

PARTICLE THEORY USED

The particle can exist in a linear combination or superposition of the two paths

This concept is applied here using qubits for computations.

QUANTUM GATES Quantum Gates are similar to classical

gates, but do not have a degenerate output. i.e. their original input state can be derived from their output state, uniquely. They must be reversible.

This means that a deterministic

computation can be performed on a quantum computer only if it is reversible.

QUANTUM PHYSICS CONCEPTS USED The following quantum physics concepts

are used in Quantum Computing. superposition Interference(constructive & destructive) Coherence Entanglement

1. SUPERPOSITION Superposition is a principle of

quantum theory

The principle of superposition claims that while we do not know what the state of any object is, it is actually in all possible states simultaneously.

Mathematically, it refers to a property of solutions to the Schrödinger equation

2.INTERFERENCE

In physics, interference is the phenomenon in which two waves superpose each other to form a resultant wave of greater or lower amplitude.

3. COHERENCE

In physics, coherence is a property of waves that enables stationary (i.e. temporally and spatially constant) interference.

4. ENTANGLEMENT

Entanglement is a term used in quantum theory to describe the way that particles of energy/matter can become correlated to predictably interact with each other regardless of how far apart they are.

APPLICATIONS OF QUANTUM COMPUTING

QUANTUM CRYPTOGRAPHYCRYPTOGRAPHY:-

Transmitting information with access restricted to the intended recipient even if the message is intercepted by others.

The process• Sender Plaintext

Cryptotext

Decryption

PlaintextRecipient

Message encryption

Key

Key ready for use

Secure key distribution

Encryption

Securetransmission

Hard Problem for conventionalencryption

THE CLASSIC CRYPTOGRAPHY Encryption algorithm and related

key are kept secret. Breaking the system is hard due to

large numbers of possible keys. For example: for a key 128 bits long

there are keys to

check using brute force. The fundamental difficulty is key

distribution to parties who want to exchange

messages.

38128 102

PKC – THE MODERN CRYPTOGRAPHY In 1970s the Public Key

Cryptography emerged. Each user has two mutually

inverse keys. The encryption key is published; The decryption key is kept

secret. Eg:- Anybody can send a

message to Bob but only Bob can read it.

RSA ALGO The most widely used PKC is the RSA

algorithm based on the difficulty of factoring a product of two large primes.

EASY PROBLEM:- Given two large primes p and q and compute

HARD PROBLEM:- Given n compute p and q.

qpn

FACTORING A PRODUCT OF TWO LARGE PRIMES The best known conventional

algorithm requires the solution time proportional to:

For p & q 65 digits long T(n) is approximately

one month using cluster of workstations

and For p&q 200 digits long T(n) is

astronomical.

])ln(ln)(lnexp[)( 3/23/1 nncnT

QUANTUM COMPUTING ALGORITHM FOR FACTORING In 1994 Peter Shor from the AT&T Bell

Laboratory showed that in principle a quantum computer could factor a very long

product of primes in seconds.

Shor’s algorithm time computational complexity is ])[(ln)( 3nOnT

THE MAIN CONTRIBUTION OF QUANTUM CRYPTOGRAPHY It solved THE KEY DISTRIBUTION

problem. It unconditionally secured the key

distribution method proposed by Charles Bennett and Gilles Brassard in 1984.

The method is called BB84.

QUANTUM KEY DISTRIBUTION

SECURITY OF QUANTUM KEY DISTRIBUTION

This makes impossible to intercept message without being detected.

WHATS THE NEED??!!?? Potential (benign) applications

- Faster combinatorial search - Simulating quantum systems

‘Spinoff’ in quantum optics, chemistry, etc.

Makes QM accessible to non-physicists Surprising connections between physics

and CS New insight into mysteries of the

quantum

GOALS & APPROACHES Key technical challenge:

prevent decoherence , or unwanted interaction with environment.

Approaches: NMR, ion trap, quantum dot,Josephson junction, opticals,etc….

THANK YOU !!!