Macroscopic Quantum Mechanics, Tunnelling, and Classical Gravity

Gravity Deborah C. Good, Lincoln D. Carr

Steen Møller Nielsen

This preprint examines macroscopic quantum systems, specifically superconducting qubits and SQUIDs within the framework of the Relativistic Coherent Vacuum Gravity Theory (rCVGT). Macroscopic quantum devices demonstrate that quantum coherence can persist in systems involving billions of electrons, occupying a regime traditionally viewed as intermediate between microscopic quantum physics and classical behavior. While standard quantum mechanics and superconducting circuit theory successfully describe these systems operationally, their existence raises foundational questions about the physical origin, stability, and breakdown of quantum coherence at macroscopic scales. In rCVGT, quantum coherence is interpreted as a physical property of a structured relativistic vacuum rather than as a purely abstract state-vector attribute. Within this perspective, macroscopic quantum states correspond to extended, low-entropy coherent vacuum configurations stabilized by superconducting order. Decoherence and measurement are interpreted as physical processes involving the degradation of vacuum coherence, consistent with (but ontologically deeper than) standard environment-induced decoherence descriptions. This work does not modify the operational form or experimentally validated predictions of quantum mechanics, superconducting circuit theory, or general relativity in the regimes considered. All standard results for qubits, SQUIDs, and macroscopic quantum tunneling remain unchanged. Instead, the paper provides a coherent physical interpretation that integrates macroscopic quantum phenomena with the vacuum-based ontology of rCVGT. The preprint is intended as a conceptual and interpretive supplement to the main rCVGT framework, clarifying how macroscopic quantum coherence, measurement, and classicality naturally fit into a vacuum-coherence-based description of gravity and spacetime. It stands independently, while supporting the broader rCVGT research program linking quantum mechanics, gravity, and emergent physical time.

Wenjie Zhong, Yubao Liu, Yanbei Chen +2 more

Macroscopic optomechanical systems offer a promising testbed for distinguishing whether gravity acts as a quantum interaction or as a classical field. Schrodinger-Newton (SN) theory is the nonrelativistic limit of semi-classical gravity where quantum matter couples to classical gravity. Based on SN theory, this work investigates how classical self-gravity affects continuous quantum state tomography of a macroscopic mechanical oscillator monitored by variable-angle homodyne detection. In the Schrodinger-Newton (SN) theory, the measurement record arises from a different conditional test mass dynamics from that in quantum-gravity (QG)/standard quantum mechanics, consequently, applying the QG-optimised reconstruction map introduces an additional state-dependent contribution. We show that this contribution makes the reconstructed covariance depend on the chosen set of tomography angles and can drive the SN covariance--after QG filtering--outside the standard Gaussian-covariance domain set by the Heisenberg uncertainty principle. We quantify the resulting QG-SN distinguishability via the Hellinger distance and analyse its dependence on measurement strength and temperature. We then formulate the same issue in the broader setting of nonlinear quantum mechanics: when the system's conditional dynamics during the readout process depends on the state being inferred, the tomographic map acquires nonlinear, model-dependent corrections to the usual Radon or Gaussian reconstruction map.

Giovanni Amelino-camelia A

Kai Marquardt, Pascal Wieland, Rolf Häfner +3 more

The ground state of Bose-Einstein condensates with attractive particle interactions is metastable. One of the decay mechanisms of the condensate is a collapse by macroscopic quantum tunneling, which can be described by the bounce trajectory as a solution of the time-dependent Gross-Pitaevskii equation in imaginary time. For condensates with an electromagnetically induced gravity-like interaction, the bounce trajectory is computed with an extended variational approach using coupled Gaussian functions and is simulated numerically exact within the mean-field approach on a spacetime lattice. It is shown that the variational computations converge very rapidly to the numerically exact result with increasing number of Gaussians. The tunneling rate of the condensate is obtained from the classical action and additional parameters of the bounce trajectory. The converged variational and numerically exact results drastically improve by several orders of magnitude the decay rates obtained previously with a simple variational approach using a single Gaussian-type orbital for the condensate wave function.

A. J. Leggett