Observation of a Classical Prethermal Discrete Time Crystal on a Superconducting Quantum Processor via Phase-Anchored State Multiplexing

Manuscript submitted to Physical Review Letters (es2026aug09_746) with Supplemental Material. Using Phase-Anchored State Multiplexing (PASM) on two IBM Heron r2 processors (ibm_marrakesh, ibm_kingston), we report an independent realization of a classical prethermal discrete time crystal on superconducting hardware through a phase-anchored protocol distinct from Floquet-driven realizations. Signature: mutual information between identically prepared qubits that peaks at 0.159 at three qubits, is modulated by the controlled-phase angle (max at phi = pi), reaches 0.722 in the PASM-H variant, is reproducible across ten replicas (Z = 39.6 sigma), is independent of physical qubit separation (Z = 34 sigma), survives controlled noise, and vanishes in control protocols (MI = 0.00013). Quantum state tomography shows the correlation is classical (quantum discord < 0.01). Full experimental record: 14 experiments, 186 circuit executions, 1.5 million measurements. A residual MI at phi = pi in the echo variant (0.0062, theory ~ 0) is reported transparently and earmarked for follow-up tests.