Why the Future Cannot be Open in the Quantum World

TL;DR

This paper argues that if quantum mechanics is complete, then the future is not open, as measurement outcomes are determined, challenging the common view that quantum indeterminacy implies an open future.

Contribution

It demonstrates that quantum mechanics, when considered complete, implies a deterministic universe, thus the future cannot be open regardless of interpretation.

Findings

Quantum mechanics implies a deterministic universe if complete.

Measurement outcomes are determined even if not predictable.

The future is not open under complete quantum mechanics.

Abstract

In this study, I argue that the future is not open if quantum mechanics is complete. An open future means that the value observed when measuring a physical quantity in the future is not determined. At first glance, quantum mechanics seems to support the open future thesis, because it cannot always predict measurement value with certainty. However, many interpretations regard quantum mechanics as deterministic. These interpretations only suggest that the quantum mechanical world can be deterministic. I argue that, although quantum mechanics cannot predict the future with certainty, the quantum mechanical world must be deterministic, and the value observed by the observer is determined. I examine the following two cases: (1) the wave-function completely describes the physical state and (2) the wave-function does not describe the physical state. Then, I argue that the future cannot be open in either case when quantum mechanics is complete.