We investigate the role of inefficiency in quantum measurements in the quantum-to-classical transition, and consistently observe the quantum-to-classical transition by coarsening the references of the measurements (e.g., when and where to measure). Our result suggests that the definition of measurement precision in quantum theory should include the degree of the observer’s ability to precisely control the measurement references.

• Received 14 July 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.010402