Gravitationally induced decoherence vs space-time diffusion: testing the quantum nature of gravity

Area of Science:

• Quantum physics
• Classical mechanics
• Gravitational physics

Background:

• Investigating hybrid systems where one component is classical and the other quantum is crucial for understanding fundamental physics.
• Previous work explored consistent dynamics of such couplings, particularly in the context of classical spacetime.
• The implications of such hybrid dynamics for quantum decoherence and classical predictability were not fully understood.

Purpose of the Study:

• To prove that hybrid quantum-classical dynamics inevitably cause decoherence in the quantum system.
• To demonstrate that this hybrid dynamics leads to a breakdown in predictability within the classical system's phase space.
• To establish a general trade-off relation between decoherence rate and classical diffusion for all classical-quantum dynamics.

Main Methods:

• Theoretical analysis of hybrid quantum-classical systems.
• Derivation of a trade-off relation governing decoherence and classical diffusion.
• Application of the trade-off relation to theories of quantum gravity.
• Analysis of experimental constraints from interferometry and mass measurements.

Main Results:

• Any hybrid quantum-classical dynamics necessarily induces decoherence in the quantum system.
• Predictability in the classical phase space breaks down due to this hybrid interaction.
• A universal trade-off exists: longer quantum coherence times necessitate stronger diffusion in the classical system.
• Gravitational theories with classical gravity interacting with quantum matter face significant restrictions based on current experimental data.

Conclusions:

• Hybrid quantum-classical dynamics are inherently linked to decoherence and classical unpredictability.
• The derived trade-off relation provides a new framework for testing theories of quantum gravity.
• Current experimental bounds from interferometry and mass measurements already constrain theories of classical gravity interacting with quantum matter.
• Future experiments can further refine these constraints by improving mass measurements and interferometry precision.