GPT5 on Barandes MMI

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Brent Meeker

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Aug 8, 2025, 4:59:20 PM8/8/25

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So I asked GPT5 about Barandes Minimal Modal interpretation. This is what it said:

🧠 MMI (Minimal Modal Interpretation): Core Ideas

Barandes’ Minimal Modal Interpretation is a realist, minimalistic, and dynamically robust interpretation that avoids many of the traditional problems with other modal interpretations. Key features:

Ontic states: The actual state of a quantum system is one of the eigenstates of its density matrix — this is the system’s real, definite state (ontic state).
No collapse: MMI maintains unitary evolution (no special collapse process) — but identifies one of the possible states as "actually real."
Contextual ontology: The real state is relative to the system's entanglement context, meaning: what is "real" depends on the system's interaction with its environment.
Probabilistic realism: The interpretation accepts that we may not know the ontic state, but one of them is real — governed by probabilities from the density matrix.

🎯 Applying MMI to the Two-Slit Experiment

🟢 1. Before any measurement (no which-way info)

The particle's wavefunction includes a superposition of both slits.
The density matrix represents this superposed state.
In MMI, no definite slit-path ontic state is assigned because there's no interaction that entangles the particle with a measuring device or environment that distinguishes the slits.
The interference pattern results because the system evolves unitarily and the real ontic state encompasses both paths.

✅ No which-way information → interference appears, because the real ontic state reflects a coherent superposition.

🔴 2. When which-way information is obtained

Placing a detector near the slits entangles the particle with the measurement apparatus (or environment).
This changes the reduced density matrix of the particle into a mixed state — corresponding to a classical probability mixture of “went through slit A” or “slit B.”
Now, in MMI, one of these eigenstates is the ontic state: the particle actually went through one slit or the other, even if we don’t know which.
Because coherence is lost (off-diagonal terms in the density matrix vanish), no interference pattern forms.

✅ Which-way information → definite ontic state assigned to one slit, destroying interference.

🔑 Key Role of "Which-Way" Information in MMI

Which-way detection entangles the particle with a system that decoheres the superposition.
This shifts the density matrix from a pure superposed state to a mixed state, forcing MMI to assign a definite (ontic) slit-path state.
The availability of which-way information (even if unobserved!) changes the context and alters what ontic states can be.

🧩 Summary

Barandes’ MMI explains the two-slit experiment by focusing on how the quantum system’s ontic state depends on entanglement and decoherence:

No which-way info → ontic state reflects superposition → interference occurs.
Which-way info → ontic state reflects definite slit path → no interference.

It preserves realism by saying the particle always has a real state, but that state depends on the system’s quantum correlations, not on subjective observation.