Enter background and philosophy

Cheung's Enter calculus treats destructive readout as an operation that consumes the measured quantum names and returns a classical record, with the surviving quantum context explicitly typed CheungEnter,CheungI. The accompanying philosophy distinguishes readout from quantum recovery, a channel from a thermal machine, and an analogy from an identification CheungPhilosophy.

We adopt finite Born and projective-update semantics. We do not claim a new derivation of those semantics outside the structural class of the Enter characterization.

In particular:

1. a consumed clock register is not a destroyed coordinate axis;

2. a classical time label is not a surviving quantum clock;

3. a residual register carrying evaluation data is not automatically a scalar quantum field;

4. a causal schedule on a supplied metric is not a derivation of that metric.

Finite instruments and reference extensions are understood in the usual completely positive framework DaviesLewis,Watrous. Every instrument identity needed for the release is established below.