Magnetic noise in macroscopic quantum spatial superposition

Sneha Narasimha Moorthy; Andrew Geraci; Sougato Bose; Anupam Mazumdar

doi:10.1103/9n6y-cc7r

paper

Magnetic noise in macroscopic quantum spatial superposition

arXiv:2504.13252 · doi:10.1103/9n6y-cc7r

Abstract

In this paper, we will show how random fluctuations in the magnetic field will jitter the paths of a matter-wave interferometer randomly, hence, decohere the quantum superposition. To create a large spatial superposition with nanoparticles, we envisage embedding a spin in a nanoparticle as a defect and applying an inhomogeneous magnetic field as in a Stern-Gerlach type experiment to create a macroscopic quantum superposition. Such matter-wave interferometers are the cornerstone for many new fundamental advancements in physics; particularly, adjacent matter-wave interferometers can use entanglement features to test physics beyond the Standard Model, test the equivalence principle, improve quantum sensors, and test the quantum nature of spacetime in a lab. In particular, we will use white and flicker noise to study the decoherence and constrain the parameters keeping in mind ambient temperatures suitable for superconducting wires embedded on a chip. We will show that to obtain a tiny spatial superposition of a nanometer separation, $Δ x \sim O (1 0^{- 9})$ m and to minimize decoherence, $Γ \leq O (\frac{ω _{0}}{2 π})$ , where $Γ$ is the decoherence and $ω_{0}$ is the frequency of the oscillator, we will need current fluctuations to be $δ I / I \leq O (1 0^{- 8})$ , which is not impossible to obtain in superconducting wire arrangements. For such tiny fluctuations, we demonstrate that the Humpty-Dumpty problem in a matter-wave interferometer arising from a mismatch in position and momentum does not cause a loss in contrast.

18 pages, 8 figures

Magnetic noise in macroscopic quantum spatial superposition

Abstract

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