Can different quantum state vectors correspond to the same physical state? An experimental test

Daniel Nigg,Thomas Monz,Jonathan Barrett,Matthew F Pusey,Markus Hennrich,Rainer Blatt,Philipp Schindler,Esteban A Martinez,Terry Rudolph

doi:10.1088/1367-2630/18/1/013007

Abstract

A century after the development of quantum theory, the interpretation of a quantum state is still discussed. If a physicist claims to have produced a system with a particular quantum state vector, does this represent directly a physical property of the system, or is the state vector merely a summary of the physicist’s information about the system? Assume that a state vector corresponds to a probability distribution over possible values of an unknown physical or ‘ontic’ state. Then, a recent no-go theorem shows that distinct state vectors with overlapping distributions lead to predictions different from quantum theory. We report an experimental test of these predictions using trapped ions. Within experimental error, the results confirm quantum theory. We analyse which kinds of models are ruled out.

Highlights

Does the quantum state correspond directly to physical reality, or does it instead represent an experimenter’s knowledge or information? If it represents information, what is this information about? Many of the controversies surrounding quantum theory are related to these basic questions
If a physicist claims to have produced a system with a particular quantum state vector, does this represent directly a physical property of the system, or is the state vector merely a summary of the physicist’s information about the system? Assume that a state vector corresponds to a probability distribution over possible values of an unknown physical or ‘ontic’ state
We report an experimental test of these predictions using trapped ions

Summary

December 2015

7 Authors to whom any correspondence should be addressed. If a physicist claims to have produced a system with a particular quantum state vector, does this represent directly a physical property of the system, or is the state vector merely a summary of the physicist’s information about the system? Assume that a state vector corresponds to a probability distribution over possible values of an unknown physical or ‘ontic’ state. A recent no-go theorem shows that distinct state vectors with overlapping distributions lead to predictions different from quantum theory.

Introduction

Different models: ψ-ontic versus ψ-epistemic

The noisy case

Experimental implementation and results

Discussion of assumptions and experimental loopholes

Conclusions