Quantum Computing: Theoretical versus Practical Possibility

TL;DR

This paper explores the fundamental and practical challenges of building scalable quantum computers, considering whether current difficulties are due to technological limits or fundamental physical laws.

Contribution

It introduces a distinction between 'strong' and 'weak' emergentist positions, analyzing whether quantum mechanics or resource scaling limits hinder quantum computing development.

Findings

Quantum computing is theoretically possible with no known physical laws forbidding it.

Scaling up qubits faces significant practical and possibly fundamental physical challenges.

The paper proposes two perspectives: breakdown of quantum mechanics or resource limitations as barriers.

Abstract

An intense effort is being made today to build a quantum computer. Instead of presenting what has been achieved, I invoke here analogies from the history of science in an attempt to glimpse what the future might hold. Quantum computing is possible in principle - there are no known laws of Nature that prevent it - yet scaling up the few qubits demonstrated so far has proven to be exceedingly difficult. While this could be regarded merely as a technological or practical impediment, I argue that this difficulty might be a symptom of new laws of physics waiting to be discovered. I also introduce a distinction between "strong" and "weak" emergentist positions. The former assumes that a critical value of a parameter exists (one that is most likely related to the complexity of the states involved) at which the quantum-mechanical description breaks down, in other words, that quantum mechanics will turn out to be an incomplete description of reality. The latter assumes that quantum mechanics will remain as a universally valid theory, but that the classical resources required to build a real quantum computer scale up with the number of qubits, which hints that a limiting principle is at work.