Lloyd, Seth. “Ultimate Limits to Computation”,Nature, August 31, 2000.

» Current laptop: speed: ~109 operations per sec. memory: ~1010 bits

» Analysis based on quantum theory

» Theoretical limit: ~1032 operations per sec. on 1016 bits

» Experimental quantum computers based on NMR to store one bit per spin of a nuclei.

Some algorithms are not feasible because they taketoo long to execute.

Recall from a previous lecture...

password length execution time

2 chars

3 chars

4 chars

5 chars

6 chars

8 chars

15 chars

Password cracking by testing all possibilities:

Q: What kind of algorithms are infeasible?Q: What kind of algorithms are infeasible?

play cards by considering all possible hands

A: Algorithms that consider all possible_________ or _________ for a significant number of values.

A: Algorithms that consider all possible_________ or _________ for a significant number of values.

play chess by analyzing all possible games

test every possible DNA gene sequence

Examples -- Consider algorithms to...

Are computers intelligent?Alan Turing

Turing Test (1950)

respondent?

More about the Turing TestMore about the Turing TestCriticisms:

Sometimes humans are not intelligent.Some intelligent behavior is not human behavior.

Turing test