A brief introduction to

Quantum computer

Alri

Moore's law

the number of transistors in a dense integrated circuit has doubled approximately every two years

——- Gordon E. Moore, the co-founder of Intel

speed and computing capacity

physical limits

atomic level

quantum theory

classical computer——>

quantum computer?

Qubit

a linear superposition of basis states

both states at the same time

two-state quantum-mechanical system

Quantum entanglement

system as a whole

one particle of an entangled pair "knows" what measurement has been performed on the other, and with what outcome

Faster-than-light Quantum mechanics

not true communication

two observers in different locations see the same system simultaneously

Energy and computing

Landauer's principle:

the erasure of n bits of information must always incur a cost of

n k T ln(2)

in thermodynamic entropy

erasure of information — necessary?

Reversible computing

the relation of the mapping from states to their successors must be one-to-one

Toffoli gate

CCNOT gate

"controlled-controlled-not" gate

any reversible circuit can be constructed from Toffoli gates

3-bit inputs and outputs : if the first two bits are set, it inverts the third bit, otherwise all bits stay the same

Toffoli gate

The Toffoli gate is reversible (but the Toffoli' used above is not). This means that any computation did with it can be

undone. This is:(a,b,c)=Toffoli(Toffoli(a,b,c))

Universality and Toffoli gate

Boolean functions ：

OR, AND ， NOT gates

NOR gates

NAND gates

Toffoli gate

NAND(a,b)=Toffoli′(a,b,1)

NOT(x)=Toffoli′(1,1,x)

AND(a,b)=Toffoli′(a,b,0)

basic quantum computers that can perform certain calculations

D-Wave Systems

512-qubit

D-Wave Two quantum computer

new era

Referenceshttps://en.wikipedia.org/wiki/Moore%27s_law

https://en.wikipedia.org/wiki/Qubit#Bit_versus_qubit

https://en.wikipedia.org/wiki/Quantum_entanglement

http://www.technologyreview.com/view/422511/the-fantastical-promise-of-reversible-computing/

https://en.wikipedia.org/wiki/Toffoli_gate

http://www.dwavesys.com/quantum-computing

Thank you!