A Bundle Isomorphism Relating Complex Velocity to Quantum Fisher Operators
This provides a novel geometric unification of stochastic gravity and quantum estimation theory, potentially impacting foundational understanding of quantum metrology in curved spacetimes.
The authors establish a bundle isomorphism between a complex velocity field arising from stochastic gravitational fluctuations and the symmetric logarithmic derivative operator, expressing the quantum Fisher information metric in terms of this velocity field and showing that its holonomy is quantized, leading to topological phases observable in atom interferometry.
We show that averaging matter dynamics over stochastic gravitational fluctuations gives rise to a complex velocity field \(η_μ = π_μ - i u_μ\) living as a section of the pullback bundle \(E = π_{2}^{*}(T^{*}M)\to \mathcal{C}\times M\). We prove that \(η_μ\) is isomorphic, via the Schrödinger representation, to the symmetric logarithmic derivative (SLD) operator \(L_μ\) on the Hilbert space \(\mathcal{H}_{x} = L^{2}(\mathcal{C})\), up to a trace-zero projection. This isomorphism \(\widetilde{\mathcal{T}}:Γ(E / \sim)\to Γ(\mathcal{L})\) is a bundle isomorphism preserving the flat \(U(1)\) connection (proved in \cite{meza2026topological}) and the quantum Fisher metric. The quantum Fisher information metric \(g_{μν}^{\mathrm{FS}}\) is expressed directly in terms of \(η_μ\) as \(g_{μν}^{\mathrm{FS}} = - \frac{4m^{2}}{\hbar^{2}}\mathrm{Re}\langle (η_μ - \langle η_μ\rangle)(η_ν - \langle η_ν\rangle)\rangle_{\mathcal{P}}\). The holonomy of \(η_μ\) is quantized, leading to topological phases observable in atom interferometry.