Matteo G A Paris Quantum Optics & Information Group

Università di Milanoqinf.fisica.unimi.it/~paris

Informatica Quantistica: Informatica Quantistica: IntroduzioneIntroduzione

Milano, 30 Maggio 2005

Title

Information is physical

Information is physical

Coding: logical bit / physical degree of freedom (superpositions and non-orthogonality)

Transmission, manipulation: Logical gates should be unitary.After interactions information carriers cannot be separately described (superpositions entanglement)

Decoding: uncertainty relations and impossibility of joint measurements

Uncertainty relations Fluctuations

Information is physical: quantum mechanics

Superpositions (coherence) Entanglement

Resource Noise

Noise Reso

Quantum Information

Impossible machines

cloning quantum repeaters limits to amplification

nonorthogonality signal discrimination

joint measurements

Quantum resources

parallelism quantum computing

entanglement teleportation dense coding

Quantum cryptography

QInf

No Clon 1

No Clon 2

State discrimination

1≠0 no way to discriminate with certainty

error probability Pe = z0 P10 + z1 P01 Pij = Tr [j i]

Optimal detection

1= >0 |>< | 0= - 1

| >= | > = z1 1 - z0

Minimum error (pure states)

Pe 1

21 1 4z0z1 0 1

2

open problems:- mixed states- asymm. sets- …

Crypto

Q Crypto 1

D cod 2

TLP

Q Calc

CTRL F

Deutsch

UnivGate1

Open problems (among many others)

Implementations QC (scalable, robust against decoherence)

Quantum algorithms Reversible computation

Characterization of entanglement

Outro

Toffoli