Classical-quantum systems breaking conservation laws

• URL: http://arxiv.org/abs/2506.15291v2
• Date: Tue, 22 Jul 2025 13:19:00 GMT
• Title: Classical-quantum systems breaking conservation laws
• Authors: Masahiro Hotta, Sebastian Murk, Daniel R. Terno,
• Abstract summary: Whether gravity must be quantized remains one of the biggest open problems in fundamental physics.<n>We consider a qubit interacting with a classical particle and demonstrate that the corresponding hybrid system violates angular momentum conservation.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Whether gravity must be quantized remains one of the biggest open problems in fundamental physics. Classical-quantum hybrid theories have recently attracted attention as a possible framework in which gravity is treated classically yet interacts consistently with quantum matter. Schemes based on completely positive dynamics satisfy most formal consistency requirements and enable a systematic treatment of quantum backreaction, but they also give rise to features that challenge conventional physical intuition, such as the breakdown of conservation laws. To illustrate this issue, we consider a qubit interacting with a classical particle and demonstrate that the corresponding hybrid system violates angular momentum conservation despite the rotational symmetry of the underlying equations of motion.

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