Search of a First Principle for Quantum Physics

Armin Uhlmann

Bernard d’Espagnat

The difference between the conceptual framework of classical physics and that of quantum physics which is due to the nonseparability property of the latter theory is better understood in specific examples. This chapter uses some specific examples to test the validity, both in classical and in quantum mechanics, of two conceptual principles. First is Reality Principle . The very concept of a reality may be criticized by philosophically minded empiricists. A widespread opinion, however, is that somehow a physical reality does exist, which should not just amount to the talks we give about it. In their search for a criterion that would make it possible to recognize elements of reality, A. Einstein, B. Podolsky, and N. Rosen had to take such considerations into account. Second, Principle of the Separability of Mechanically Isolated Systems, one can easily guess that this second principle, which remains somewhat implicit in the work of Einstein and his colleagues may well be the source of insuperable difficulties.

Jesús Rubio

Combining quantum and Bayesian principles leads to optimality in metrology, but the optimization equations involved are often hard to solve. This Letter mitigates this problem with a class of measurement strategies for quantities isomorphic to location parameters, which are shown to admit a closed-form optimization. The resulting framework admits any parameter range, prior information, or state, and the associated estimators apply to finite samples. As an example, the metrology of relative weights is formulated from first principles and shown to require hyperbolic errors. The primary advantage of this approach lies in its simplifying power: it reduces the search for good strategies to identifying which symmetry leaves a state of maximum ignorance invariant. This will facilitate the application of quantum metrology to fundamental physics, where symmetries play a key role. Published by the American Physical Society 2024

Miguel Ferrero, Alwyn van der Merwe

Alexandru C. V. Ceapa

The relativistic energy-momentum relationship is far more subtle than it seems to be at a first sight. As concerns the relativistic quantum mechanics, its underlying equations were deduced from, or in relation with the relativistic energy-momentum relationship by means of the principle of correspondence. Without a clear physical role and meaning associated, the matrices of the Dirac equation seemed to confirm that the principle of the physical determination of equations would not be proper to the new quantum mechanics. Therefore, we have to search for genuine physical information in the terms of the underlying equations of the relativistic quantum mechanics. This information concerns a level of structure of matter “even below that on which nuclear transformations take place.”

Brian C. Hall