Intermediate-time behavior of generalized CNOT-fan-out dynamics

Determine what occurs at intermediate times for generalized CNOT-fan-out quantum-circuit dynamics and whether such dynamics generates past redundancy for events occurring at times strictly between the initial and final times.

Background

The paper shows that generalized CNOT-fan-out dynamics applied to a product initial state generates quantum Darwinism and past redundancy for pointer-basis events at the initial time. However, because the circuit representation specifies the overall unitary action without uniquely specifying a continuous-time implementation, the status of records for events at intermediate times is left unresolved.

References

Since eqn~(\ref{eq:U CNOT-fan-out}) describes the unitary action of a quantum circuit, it is unclear what happens at an intermediate time $s\in(0,t)$.

— Redundant Records of the Past: Unifying Quantum Darwinism and Decoherent Histories  (2610.09845 - Strasberg, 7 Oct 2026) in Footnote following Section 3.2, “Connection to QD”