Speedup in quantum computation is associated with attenuation of processing probability

TL;DR

This paper argues that quantum speedup is fundamentally limited because it comes with a reduction in detection probability, resulting in no effective speedup over classical devices on average.

Contribution

It demonstrates that quantum speedup is inherently linked to attenuation of processing probability, challenging the assumption of unbounded quantum computational advantage.

Findings

Quantum speedup involves attenuation of detection rates.

No effective speedup over classical devices when averaged.

Quantum parallelism does not guarantee exponential speedup.

Abstract

Quantum coherence allows the computation of an arbitrary number of distinct computational paths in parallel. Based on quantum parallelism it has been conjectured that exponential or even larger speedups of computations are possible. Here it is shown that, although in principle correct, any speedup is accompanied by an associated attenuation of detection rates. Thus, on the average, no effective speedup is obtained relative to classical (nondeterministic) devices.