Quantum Time-Symmetric Interpretation: Local Causality, Emergent Irreversibility, and the Dynamical Origin of the Arrow of Time

Abstract

The fundamental equations of quantum mechanics are time-symmetric, yet measurements generate irreversible records and a one-way causal structure at macroscopic scales. The Quantum Time-Symmetric Interpretation (QTSI) explains this contrast as emergent rather than fundamental. Isolated quantum systems are described by a two-component temporal bispinor containing both forwardand backward-evolving amplitudes, coupled through a pseudo-Hermitian SU(1,1) Hamiltonian. Their coupling is governed by a mixing parameter Δ that depends on a macroscopic amplification fraction φ = N m /N t , where N t is the total number of relevant microscopic events and N m is the number that trigger irreversible macroscopic records. The associated retrocausal coherence time τ_RC = ħ/|Δ(φ)| is the characteristic timescale on which ψ+ and ψ− mix. As φ increases, τ_RC grows, temporal interference requires progressively longer times to form, and in the limit φ → 1 it becomes physically inaccessible. Δ vanishes, the two temporal sectors decouple dynamically, time symmetry is broken, and the system enters the irreversible classical regime. Standard quantum mechanics is recovered in this limit. The Born rule emerges naturally as ψ− → 0, since |ψ+ + ψ−|² reduces to |ψ+|² without any additional postulate. QTSI is a locally causal, ontologically realist, no-signaling interpretation: Bell correlations arise from time-symmetric global boundary conditions rather than nonlocal influences. Observable deviations from standard quantum mechanics are predicted in weakly monitored interferometric regimes, including the visibility formula V(φ) = V₀[1−exp(−T_av(1−φ)Δ₀/ħ)] — which decreases with monitoring fraction φ and reduces to V ≈ V₀(1−φ) for T_avΔ₀/ħ ≫ 1 — and a new three-slit signature in which the Fourier spectrum of the intensity pattern contains phase-coherent sum-phase peaks absent in standard quantum mechanics, whose Fourier amplitude scales as (1−φ) with the monitoring fraction.