Module phase 

Phase — i^k factors arising from Pauli algebra, with k ∈ {0, 1, 2, 3}.

Multiplication of two Pauli bitstrings produces an i^k factor wherever X- and Z-bits coincide (see PauliString::mul_assign); callers fold this into the relevant Complex64 coefficient at the boundary (PauliSum, BuildAccumulator, channel apply). Phase centralizes that arithmetic so every site uses the same combine/apply rules instead of open-coded u8 & 3 masks and four-arm match statements.

Examples

Combine phases with + (mod 4) and fold one into a Complex64 coefficient with Phase::apply:

use paulistrings::Phase;
use num_complex::Complex64;

let p = Phase::I + Phase::I; // i · i = -1
assert_eq!(p, Phase::MINUS_ONE);

let folded = Phase::I.apply(Complex64::new(2.0, 3.0)); // i · (2 + 3i) = -3 + 2i
assert_eq!(folded, Complex64::new(-3.0, 2.0));

Structs

Phase

A phase factor i^k where k ∈ {0, 1, 2, 3}.