Quantum Computation: What is it and Why?

77° Fiera del Levante22 September 2013

16,40Pad.7

Who am I?

Degree in Mathematics

Innovaction Lab, Puglia

MasterEuropei

stefano franco stefano@alumnimathematica.org

Just two questions:

1. What is Quantum Computation?

2. Why Quantum Computation?

“God does not throw dice”(Einstein, 4 December 1926)

1. What is Quantum Computation?

A quantum computer is a computation device that makes direct use of quantum-mechanical phenomena to perform operations on data

1.1 Historical notes

Turing machine

Alan (1912-1954)

Post-IIWW period

physics is strictly connected to computation

- quantum computation is possible

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-

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1970Stephene Wiesner invents conjugate coding

- quantum computation is possible

- quantum computation is different from classical computation

-

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1973Charles H. Bennett shows that computation can be done

reversibly

- quantum computation is possible

- quantum computation is different from classical computation

- quantum computation is necessary for some computational devices

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1981Richard Feynmann (Physic Nobel Prize)

1.2 Bit vs Qubit

...and the microscopic world?

Bit

Curiosity: how many information can bestored by a qubit?

Exactly 2, like a classical bit(Holevo, 1973)

Qubit

- quantum computation is possible

- quantum computation is different from classical computation

- quantum computation is necessary for some computational devices

- quantum computation is better than the classical one

2. Why Quantum Computation?

Quantum computers are the only model of computation that escape the limitations on computation imposed by the extended Church-Turing thesis

“a function is algorithmically computable if and only if it is computable by a Turing machine. Besides the machines conserve the same size order resolution time”

Consequences (potentially and not formally):

● quantum computers are faster

● quantum computers are cheaper

processor's performances and the number of transistors per square inch on integrated circuits doubled approximately every 18 months

(Moore's Law)

(University of Cambridge)http://www.doitpoms.ac.uk/tlplib/electromigration/printall.php

- quantum computation is possible

- quantum computation is different from classical computation

- quantum computation is necessary for some computational devices

- quantum computation is better than the classical one because quantum computers resolve better some computational algorithms

don't you believe it?

2.1 EPR Paradox (1935)

Can quantum mechanics be complete?

Assumption

1. Physics reality

2. Locality

3. Completeness

There exist local hidden variables!

Bell's Inequality (1964)(experimentally Aspect and co-workers, 1981)

“There does not exist any local variable theory consistent with outcomes of quantum physics”

Consequences Entanglement is not paradossal Quantum correlations in an EPR pair are “stronger” than

classical correlations and create more powerful computational performances

...and now?

● D-wave- Founded in 1999- 13 February 2007, Orion prototype

● Google2009, first result on a quantum computer

● “D-wave skeptic”- Umesh Vazirani, Berkley - Scott Aaronson, MIT Boston

In the world...

...and in Italy?

None (or almost)

#IQCC Italian Quantum Computer Community

Alumni Mathematica,the new way to think math!

www.alumnimathematica.org stefano@alumnimathematica.org