Three myths about quantum computing — Part 1: Exponential size state space

13 Jul

Mamuta memuāri

This is the first post in the series on myths about quantum computing. In this post I will discuss the first misconception about quantum computers—that the exponential size of their state space is the main feature that distinguishes them from their classical cousins—and explain why this should not be used as an argument to suggest that quantum computers are likely to be more powerful than the classical ones.

Consider a system S with states labelled by n-bit strings. Assume that S is initialized in all-zeroes state “00…0” and undergoes some kind of physical evolution. Let us consider three scenarios.

Deterministic classical world

If the evolution is deterministic, then one can specify the current state of the system by giving the corresponding label. Thus, one needs n bits of information to describe the state in this case.

Quantum world

If S is a quantum system, it can be…

View original post 443 more words

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: