Quantum Physics


Limitation on Effective Degree of Quantum Parallelism

Authors: Masataka Ohta

Consider a binary quantum channel with binary states |0> and |1> as an output channel of some quantum computation device and assume that, if the channel is used as a classical binary channel where |0> and |1> represent bit values of 0 and 1, respectively, the channel has small error probability of p. Then, |0> transmitted over the channel will typically be sqrt(1-p)|0> + exp(i*theta)|1> (0 ≤ theta < 2*pi). That is, error of the channel makes|0> and sqrt(1-p)|0> + exp(i*theta)|1> indistinguishable, which means different results of parallel execution of the device can’t be represented by |0> and sqrt(1-p)|0> + exp(i*theta)|1>. As representing N parallel binary results needs 2^N distinguishable states, effective degree of quantum parallelism of the device, which is defined as degree of parallelism of binary results with arbitrary small error probability by ideal encoding and ideal error correction, is limited by log2(π/2*sqrt(p) + 1). That is, in practice, quantum computers are only as powerful as classical ones. Then, a brief introduction on modern communication technology over photons is provided to show that capacity of a binary quantum channel is almost twice better than quantum physicists had thought, that a classical state representing an entangled state exists and that“qubit”is a bad idea. Finally, it is shown that, without error caused by noise, ideal classical computers can be arbitrary fast.

Comments: 4 Pages.

Download: PDF

Submission history

[v1] 2017-11-04 15:12:41
[v2] 2018-02-14 08:58:42

Unique-IP document downloads: 24 times

Vixra.org is a pre-print repository rather than a journal. Articles hosted may not yet have been verified by peer-review and should be treated as preliminary. In particular, anything that appears to include financial or legal advice or proposed medical treatments should be treated with due caution. Vixra.org will not be responsible for any consequences of actions that result from any form of use of any documents on this website.

Add your own feedback and questions here:
You are equally welcome to be positive or negative about any paper but please be polite. If you are being critical you must mention at least one specific error, otherwise your comment will be deleted as unhelpful.

comments powered by Disqus