symop.polynomial.kernels.measurements.number

Polynomial number-measurement kernels.

This package provides backend implementations of photon-number measurement for polynomial state representations.

It includes support for three measurement modes:

• observation: compute full probability distributions without modifying the state

• detection: sample outcomes and return post-measurement states

• postselection: condition on a specified outcome and return the corresponding branch

Both single-target number measurement and joint per-port number measurement are supported. The behavior is controlled by the measurement resolution specified in the semantic action.

Structure

The implementation is organized into:

• common:

  Shared structural logic for resolving targets, counting quanta, and projecting states onto number sectors.

• observe:

  Non-destructive evaluation of number statistics.

• detect:

  Stochastic sampling of number outcomes and state collapse.

• postselect:

  Deterministic conditioning on specified number outcomes.

Notes

The implementation operates on symbolic polynomial representations of quantum states. Number measurement is evaluated structurally by counting creation operators associated with selected mode signatures.

For density states, probabilities are obtained from traces of projected density operators. For ket states, probabilities are computed from squared norms of projected states.

Joint per-port measurement extends the outcome space to tuples of number outcomes, one per selected port.

Modules

common	Common helpers for polynomial number measurement.
detect	Detection kernel for polynomial density-state number measurement.
observe	Observation kernels for polynomial number measurement.
postselect	Postselection kernel for polynomial density-state number measurement.