2017/06/27 by F. Piacentini, Fabrizio Piacentini, A. Avella +20
Computer Science · Physics and Astronomy · #Advanced Thermodynamics and Statistical Mechanics #Measure (data warehouse) #Observable #Open quantum system #Photon #Physics #Quantum #Quantum Information and Cryptography #Quantum Mechanics and Applications #Quantum dynamics #Quantum mechanics #Quantum operation #Quantum probability #Quantum process #Quantum statistical mechanics #Statistical physics #Theoretical physics #quant-ph
paper · pdf · doi:10.1038/nphys4223
published as Nature Physics 13, pages 1191-1194 (2017) · Nature Physics, in press (this version corresponds to the one initially submitted to Nature Physics)
arxiv created 2017/06/27 · openalex publication_date 2017/08/14 · arxiv updated 2018/02/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Quantum mechanics, one of the keystones of modern physics, exhibits several peculiar properties, differentiating it from classical mechanics. One of the most intriguing is that variables might not have definite values. A complete quantum description provides only probabilities for obtaining various eigenvalues of a quantum variable. These and corresponding probabilities specify the expectation value of a physical observable, which is known to be a statistical property of an ensemble of quantum systems. In contrast to this paradigm, we demonstrate a unique method allowing to measure the expectation value of a physical variable on a single particle, namely, the polarisation of a single protected photon. This is the first realisation of quantum protective measurements.