# Quantum computing

Quantum computing studies theoretical computation systems (quantum computers) that make direct use of quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data.

## Quotes

* We show that Shor's algorithm, the most complex quantum algorithm known to date, is realizable in a way where, yes, all you have to do is go in the lab, apply more technology, and you should be able to make a bigger quantum computer … It might still cost an enormous amount of money to build — you won’t be building a quantum computer and putting it on your desktop anytime soon — but now it’s much more an engineering effort, and not a basic physics question.
** Isaac Chuang, as quoted in "The beginning of the end for encryption schemes?" in MIT News (3 March 2016)
* Quantum computation is … nothing less than a distinctly new way of harnessing nature … It will be the first technology that allows useful tasks to be performed in collaboration between parallel universes, and then sharing the results.
** David Deutsch, in The Fabric of Reality (1997), Ch. 9 : Quantum Computers
* Turning to quantum mechanics, we know immediately that here we get only the ability, apparently, to predict probabilities. Might I say immediately, so that you know where I really intend to go, that we always have had (secret, secret, close the doors!) we always have had a great deal of difficulty in understanding the world view that quantum mechanics represents. At least I do, because I'm an old enough man that I haven't got to the point that this stuff is obvious to me. Okay, I still get nervous with it. And therefore, some of the younger students ... you know how it always is, every new idea, it takes a generation or two until it becomes obvious that there's no real problem. It has not yet become obvious to me that there's no real problem. I cannot define the real problem, therefore I suspect there's no real problem, but I'm not sure there's no real problem. So that's why I like to investigate things. Can I learn anything from asking this question about computers—about this may or may not be mystery as to what the world view of quantum mechanics is? So I know that quantum mechanics seem to involve probability—and I therefore want to talk about simulating probability.
** Richard Feynman, "Simulating Physics with Computers" in International Journal of Theoretical Physics (1982)
* Back in the 1940s, researchers were just discovering how to use vacuum tubes as simple switches. … These switches could then form logic gates, which could be linked together to form the first logic circuits. That’s where we’re at now with quantum processors. We have verified that all the components work. The next step is to engineer the smallest, yet most interesting circuit possible.
** Jungsang Kim, as quoted in "Building the World’s First Quantum Computer" by Ken Kingery in Duke Broadband (11 February 2016)
* In less than ten years quantum computers will begin to outperform everyday computers, leading to breakthroughs in artificial intelligence, the discovery of new pharmaceuticals and beyond. The very fast computing power given by quantum computers has the potential to disrupt traditional businesses and challenge our cyber-security. Businesses need to be ready for a quantum future because it's coming.
** Jeremy O'Brien, as quoted in "Quantum computing is coming—are you prepared for it?" at Phys.org (20 January 2016)

## External links

* "Quantum Computing" by Amit Hagar at Stanford Encyclopedia of Philosophy
* Visualized history of quantum computing
* Quantum Annealing and Computation: A Brief Documentary Note, A. Ghosh and S. Mukherjee
* Maryland University Laboratory for Physical Sciences: conducts researches for the quantum computer-based project led by the NSA, named 'Penetrating Hard Target'.
* Quantum Annealing and Analog Quantum Computation by Arnab Das and BK Chakrabarti
* Quantum computing for the determined – 22 video lectures by Michael Nielsen
* Video Lectures by David Deutsch
* Lectures at the Institut Henri Poincaré (slides and videos)
* Online lecture on An Introduction to Quantum Computing, Edward Gerjuoy (2008)
* Quantum Computing research by Mikko Möttönen at Aalto University (video) on YouTube