Single-particle interference: SMM/DTT and relational quantum mechanics

01The question behind this comparison

Single-particle interference is interference between alternative amplitudes contributing to one detection event. The particle number can be one while the quantum state has support on several paths. An interference pattern accumulates over many trials because the relative phase changes the probability of each individual detection; it does not require two particles to collide at the detector.

The SMM/DTT idea of sequential inner production offers a possible physical narrative for how alternative contributions belong to one completed event. Its useful mathematical content would be a coherent rule for combining those contributions before registration. A classical source that randomly chooses one path and retains only its label produces a mixture, not an interference pattern. Phase memory, a recombination operation and the measurement context therefore carry the decisive explanatory work. ^{[3] [4]}

02The SMM/DTT starting point

The Single Monad Model begins with one nonspatial generative source. The Duality of Time Theory distinguishes the source’s inner production from the outer order in which completed records become accessible. Its six inner levels are nested functional roles of one process: a higher role organizes lower-level work. The seventh is the completion or observation interface. They are neither six independent clocks nor six additional time coordinates.

This distinction supplies a useful research question: which features of an observed world can follow from the way a source produces, retains and releases information? A concrete answer needs a state space, an autonomous update, retained memory and a rule connecting completion to an accessible measurement. In the constructions discussed here, those mathematical ingredients are stated explicitly. A successful finite example establishes what its specified mechanism can do; further arguments connect it to physical particles, spacetime or universal laws. ^[1]

03How the comparator works

Relational quantum mechanics treats physical quantities and state assignments as relative to interactions between systems. An observer is any relevant physical system, not necessarily a conscious mind. What is definite relative to one system need not be represented by the same state relative to an external system that has not yet interacted with it. Communication and subsequent interactions are part of the physical account of how records are compared.

DTT’s separation of generation from accessible records can be formulated in this language when completion is indexed to a receiving system. A universal outer archive, by contrast, would add an observer-independent structure beyond Rovelli’s original proposal. Neither choice is settled merely by saying that observations occur. The useful comparison concerns exactly which system retains a record, which interactions make it accessible, and which consistency conditions connect descriptions. Relational quantum mechanics does not derive the six inner levels, while their presence alone does not decide whether completion should be universal or relational. ^[2]

04The decisive comparison

Relational quantum mechanics connects an interference claim to the systems that retain which-path information. Relative to a coherent laboratory description, path amplitudes can remain available for recombination; an interaction that creates a durable path record changes the physical relation being tested. DTT can express the same structure through source memory and a completion interface whose accessible records depend on the receiving system and the permitted measurement.

This correspondence does not make consciousness a switch that turns interference off. The relevant event is an interaction capable of correlating a physical marker with the path, whether or not anyone reads it. Nor does relationality mean that arbitrary observer descriptions predict contradictory detector statistics once their records are compared. A DTT model must say which completion is local to a receiver and how different completed descriptions agree after communication. Its useful contribution could be a quantitative access rule for retained phase, explaining when an observer can erase a marker or recover a fringe. A globally unique source history is an extra ontological commitment beyond that relational calculation. ^{[2] [3] [4]}

05Worked benchmark

Use an ideal balanced Mach–Zehnder interferometer. After the first beam splitter the path state is (|0⟩+|1⟩)/√2. A phase plate multiplies the second component by e^{iφ}. With a second balanced recombiner in the corresponding phase convention, the first output amplitude becomes (1+e^{iφ})/2. Its probability is cos²(φ/2), and the other output has probability sin²(φ/2).

For φ=0 every ideal trial reaches the first output; for φ=π none does; for φ=π/2 the outputs are equiprobable. If an environment records the paths in states with overlap γ, the interference term becomes Re(γe^{iφ}) and the visibility is |γ|. This calculation explains precisely what an inner-time mechanism must preserve: the relative phase and the coherence between alternatives. Changing the duration of private work while keeping these quantities and the registered phase fixed produces no new interference prediction. ^{[3] [4]}

06What follows for the source programme

The comparison rewards a model that identifies why a completion event combines amplitudes coherently, and why which-path information changes that combination. A finite-state simulation can exhibit the mechanism explicitly. Its result is an implementation of the interference law until independent restrictions on phase generation, memory capacity or recombination create a new testable relationship. A claimed fringe shift needs a formula tied to measured settings rather than an adjustable inner duration. ^{[3] [4]}

THE SAME QUESTION, DIFFERENT STARTING POINTS

The comparison at a glance

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