[Paper Review] Comment on "A Spin Entanglement Witness for Quantum Gravity" and on "Gravitationally Induced Entanglement between Two Massive Particles is Sufficient Evidence of Quantum Effects in Gravity"

Charis Anastopoulos, B. L. Hu|arXiv (Cornell University)|Apr 30, 2018

Biofield Effects and BiophysicsMedicine17 citations

TL;DR

This comment challenges the assumption that gravity-induced entanglement via Newtonian forces can serve as definitive evidence for quantum gravity. It argues that such entanglement is insensitive to whether gravity's fundamental degrees of freedom are quantum or classical, undermining the claim that this phenomenon proves quantum effects in gravity.

ABSTRACT

This is a comment on articles Phys. Rev. Lett. 119, 240401 (2017) [arXiv:1707.06050] and Phys. Rev. Lett. 119, 240402 (2017) [arXiv:1707.06036]. We argue that gravity-induced entanglement by Newtonian forces is agnostic to the quantum or classical nature of the gravitational true degrees of freedom.

Motivation & Objective

• To challenge the interpretation of gravity-induced entanglement as evidence for quantum gravity.
• To clarify that Newtonian gravitational interactions do not distinguish between quantum and classical gravity.
• To highlight the ambiguity in using entanglement as a witness for quantum gravitational degrees of freedom.

Proposed method

• Analyzing the entanglement mechanism induced by Newtonian gravitational potentials between two massive particles.
• Examining the role of the gravitational field's degrees of freedom in the entanglement process.
• Applying quantum field theory techniques to assess the nature of the gravitational interaction in the entanglement protocol.
• Demonstrating that the same entanglement can arise even if gravity is treated as a classical field.
• Using formal field-theoretic reasoning to show that the entanglement witness is insensitive to the quantum or classical character of gravity.
• Contrasting the assumptions in the original papers with the implications of treating gravity as a classical background field.

Experimental results

Research questions

• RQ1 Can Newtonian gravity-induced entanglement between massive particles serve as a definitive witness for quantum gravity?
• RQ2 Does the entanglement generated by gravitational potential alone reveal the quantum nature of gravity?
• RQ3 Is the entanglement effect sensitive to whether the gravitational field is quantized or classical?
• RQ4 Can a classical gravitational field reproduce the same entanglement statistics as a quantum one in this setup?
• RQ5 What does this imply for the validity of using such entanglement as evidence of quantum gravitational effects?

Key findings

• Entanglement induced by Newtonian gravitational forces does not depend on the quantum or classical nature of the gravitational field's true degrees of freedom.
• The same level of entanglement can be generated even if gravity is treated as a classical background field.
• The proposed entanglement witness is therefore agnostic to whether gravity is fundamentally quantum or classical.
• The mechanism of entanglement via Newtonian potential does not provide evidence for quantum gravitational effects.
• The conclusion that such entanglement proves quantum gravity is not logically supported by the formalism presented.
• The paper undermines the claim that this setup constitutes sufficient evidence for quantum gravity.