# A quantum prediction as a collection of epistemically restricted classical predictions

### APA

Braasch, W. (2021). A quantum prediction as a collection of epistemically restricted classical predictions. Perimeter Institute. https://pirsa.org/21090018

### MLA

Braasch, William. A quantum prediction as a collection of epistemically restricted classical predictions. Perimeter Institute, Sep. 24, 2021, https://pirsa.org/21090018

### BibTex

@misc{ pirsa_21090018, doi = {10.48660/21090018}, url = {https://pirsa.org/21090018}, author = {Braasch, William}, keywords = {Quantum Foundations}, language = {en}, title = { A quantum prediction as a collection of epistemically restricted classical predictions}, publisher = {Perimeter Institute}, year = {2021}, month = {sep}, note = {PIRSA:21090018 see, \url{https://pirsa.org}} }

William Braasch Dartmouth College

## Abstract

A toy model due to Spekkens is constructed by applying an epistemic restriction to a classical theory but reproduces a host of phenomena that appear in quantum theory. The model advances the position that the quantum state may be interpreted as a reflection of an agent’s knowledge. However, the model fails to capture all quantum phenomena because it is non-contextual. Here we show how a theory similar to the one Spekkens proposes requires only a single augmentation to give quantum theory for certain systems. Specifically, one must combine all possible epistemically restricted classical accounts of a quantum experiment. The rule for combination is simple: sum the nonrandom parts of all classical predictions to arrive at the nonrandom part of the quantum prediction.