# BB84 - QuantumCryptography QingqingYuan Outline...

This preview shows pages 1–7. Sign up to view the full content.

Quantum Cryptography Qingqing Yuan

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Outline No-Cloning Theorem BB84 Cryptography Protocol Quantum Digital Signature
One Time Pad Encryption Conventional cryptosystem: Alice and Bob share N random bits b 1 …b N Alice encrypt her message m 1 …m N  b 1 m 1 ,…,b N m N   Alice send the encrypted string to Bob Bob decrypts the message: (m j b j ) b j  = m j   As long as b is unknown, this is secure Can be passively monitored or copied

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Two Qubit Bases Define the four qubit states: {0,1}(rectilinear) and {+,-}(diagonal) form an orthogonal  qubit state. They are indistinguishable from each other. - = - + = + ) 1 0 ( ) 1 0 ( 1 0 2 1 2 1
No-Cloning Theorem |q  =  α |0 + β |1 To determine the amplitudes of an unknown qubit, need  an unlimited copies It is impossible to make a device that perfectly copies an unknown qubit. Suppose there is a quantum process that implements: |q,_ ⟩→ | q,q Contradicts the unitary/linearity restriction of quantum physics

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Wiesner’s Quantum Money A quantum bill contains a serial number N, and 20 random  qubits from {0,1,+,-} The Bank knows which string {0,1,+,-} 20  is associated with  which N The Bank can check validity of a bill N by measuring the  qubits in the proper 0/1 or +/- bases A counterfeiter cannot copy the bill if he does not know the  20 bases
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 12/27/2011 for the course CMPSC 290h taught by Professor Chong during the Fall '09 term at UCSB.

### Page1 / 22

BB84 - QuantumCryptography QingqingYuan Outline...

This preview shows document pages 1 - 7. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online