No-Go Theorems Face Background-Based Theories for Quantum Mechanics

Andréa Oldofredi

Navid Siami

Realism defined in EPR paper as “In a complete theory there is an element corresponding to each element of reality.” Bell showed that there is a forbidden triangle (Realism, Quantum Statistics, and Locality), and we are only allowed to pick two out of three. In this thesis, we investigate other inequalities and no-go theorems that we face. We also discuss possible Hidden Variable Models that are tailored to be consistent with Quantum Mechanics and the specific no-go theorems. In the special case of the Leggett Inequality the proposed hidden variable is novel in the sense that the hidden variable is in the measurement device rather than the wave-function.

Ehsan Erfani Maharat, Mohsen Sarbishaei, Ali Ahanj

Theoretical physics has faced many challenges since the advent of quantum mechanics. Recently, Frauchiger and Renner have presented a no-go theorem, which makes quantum mechanics more controversial. However, from our perspective, the process of proving appears questionable. Therefore, we discuss the validity of their proof approach in this letter. Here, we propose a simple thought experiment that clarifies how correctly the attributed quantum state can be written in problems similar to Frauchiger and Renner's Gedankenexperiment. In the next step, with the help of the correct form of the quantum state, it is demonstrated that a fallacy occurred in the proof of the no-go theorem, which means it cannot be valid because of the wrong proof. Ultimately, getting help from Hardy's paradox, we investigate whether there is an approach to modify their proof in order to lend the no-go theorem validity.

Pieter E. Vermaas

Hui-Ran Li, Ming‐Xing Luo, Hong Lai

Louis Vervoort

Usually the 'hidden variables' of Bell's theorem are supposed to describe the pair of Bell particles. Here a semantic shift is proposed, namely to attach the hidden variables to a stochastic medium or field in which the particles move. It appears that under certain conditions one of the premises of Bell's theorem, namely 'measurement independence', is not satisfied for such 'background-based' theories, even if these only involve local interactions. Such theories therefore do not fall under the restriction of Bell's no-go theorem. A simple version of such background-based models are Ising models, which we investigate here in the classical and quantum regime. We also propose to test background-based models by a straightforward extension of existing experiments. The present version corrects an error in the preceding version.