Schrödinger’s Cat in PODA Observation Geometry: Coherent Evolution, Record Formation, and Experimental Tests

Schrödinger’s cat asks how a coherent microscopic event can leave a single, durable macroscopic record. We construct a finite-apparatus model within the physical–observation dual-axis (PODA) framework, using specified quantum representations and apparatus couplings. A common action supplies the mode interactions used for source preparation and controlled amplification. For the resulting orthogonal two-branch states, entanglement negativity across the record bipartition and trace distance from the incoherent mixture equal half the full recombination visibility. Gaussian pointers determine finite-resolution probabilities and conditional states, while a canonical-reservoir construction prepares the event selector with a bounded error. To describe individual records, we retain the complete wavefunction and let actual pointer and memory coordinates follow its natural probability current. Their joint motion reproduces the statistics of successive readouts under the stated conditions. After branch preparation, a finite sequence of smooth, predetermined readout and writing gates admits an autonomous Hamiltonian with positive apparatus kinetic coefficients. We prove almost-sure global existence and Born equivariance for this apparatus, and derive bounds on terminal record errors and retention failure over a finite interval. This realization permits individual records to coexist with full-state coherence without requiring additional environmental decoherence for record formation. Three proposed qubit–cavity experiments test write–erase recovery, finite-resolution backaction, and single-mode revival. Their count probabilities and calibration requirements lead to quantitative tests of the model and conditional bounds on additional irreversible damping.