Struct PauliString 

#[repr(C)]
pub struct PauliString<const W: usize> {
    pub x: [u64; W],
    pub z: [u64; W],
}

A Pauli operator on up to 64 · W qubits.

Layout is #[repr(C)] so the type is Pod and can be reinterpreted as bytes for serialization or upload to a GPU device. There is no stored phase: multiplication returns the i^k phase as a separate Phase and callers fold it into their coefficient at the boundary.

Ord is the load-bearing trait (the engine is sort-based, not hashmap-based).

Examples

use paulistrings::PauliString;

let p = PauliString::<1>::x(3);
assert_eq!(p.weight(), 1);
assert!(p.commutes_with(&PauliString::<1>::x(0)));

Fields

x: [u64; W]

X-part bitmask: bit q is set iff the Pauli on qubit q has an X-component (i.e. is X or Y).

z: [u64; W]

Z-part bitmask: bit q is set iff the Pauli on qubit q has a Z-component (i.e. is Z or Y).

Implementations

impl<const W: usize> PauliString<W>

pub const fn identity() -> Self

Identity Pauli string (all qubits I).

Examples

use paulistrings::PauliString;

let id = PauliString::<1>::identity();
assert_eq!(id.weight(), 0);

pub fn x(qubit: u32) -> Self

Single-qubit X Pauli on qubit.

Panics

Panics in debug builds if qubit >= 64 · W.

Examples

use paulistrings::PauliString;

let p = PauliString::<1>::x(2);
assert_eq!(p.x, [0b100]);
assert_eq!(p.z, [0]);

pub fn y(qubit: u32) -> Self

Canonical Pauli Y = (1, 1) on qubit. The i factor in Y = i · X · Z is the caller’s concern — fold it into a Phase or coefficient at the boundary.

Panics

Panics in debug builds if qubit >= 64 · W.

pub fn z(qubit: u32) -> Self

Single-qubit Z Pauli on qubit.

Panics

Panics in debug builds if qubit >= 64 · W.

pub fn weight(&self) -> u32

Number of non-identity qubits (Hamming weight of x | z).

Examples

use paulistrings::PauliString;

let mut p = PauliString::<1>::x(0);
p.mul_assign(&PauliString::<1>::z(1));
assert_eq!(p.weight(), 2);

pub fn mul_assign(&mut self, other: &Self) -> Phase

Multiply self * other in place. Returns the i^k phase factor such that the true product is phase · self_after_xor.

Examples

X · Z = -i·Y: the bits XOR to Y and the phase is -i.

use paulistrings::{PauliString, Phase};

let mut p = PauliString::<1>::x(0);
let phase = p.mul_assign(&PauliString::<1>::z(0));
assert_eq!(p, PauliString::<1>::y(0));
assert_eq!(phase, Phase::MINUS_I);

pub fn mul(self, other: &Self) -> (Self, Phase)

Value-returning multiply: (self * other, phase).

Not implemented as std::ops::Mul because the operation also returns a Phase — calling sites need both the bits and the phase to fold into a Complex64 coefficient at the boundary.

pub fn is_within(&self, num_qubits: usize) -> bool

true iff every set bit lies on a qubit index < num_qubits.

The engine and built-in channels preserve this bound by construction (a channel only flips bits inside Channel::support, which is bounded at Circuit build time), so this check is not on the hot path. Use it in debug_assert! at boundaries with custom Channel impls, in PauliSum::assert_invariants, and in tests that exercise the invariant directly.

Panics

Panics in debug builds if num_qubits > 64 · W.

pub fn commutes_with(&self, other: &Self) -> bool

true iff self and other commute as Pauli operators.

Examples

use paulistrings::PauliString;

// X and Z anticommute.
assert!(!PauliString::<1>::x(0).commutes_with(&PauliString::<1>::z(0)));
// X on disjoint qubits commutes with anything on the other qubit.
assert!(PauliString::<1>::x(0).commutes_with(&PauliString::<1>::z(1)));

Trait Implementations

impl<const W: usize> Clone for PauliString<W>

fn clone(&self) -> PauliString<W>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<const W: usize> Debug for PauliString<W>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<const W: usize> Default for PauliString<W>

fn default() -> Self

Returns the “default value” for a type.

impl<const W: usize> Hash for PauliString<W>

fn hash<H: Hasher>(&self, state: &mut H)

Auxiliary; only used by BuildAccumulator (§8.2). Not on the hot path.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<const W: usize> Ord for PauliString<W>

fn cmp(&self, other: &Self) -> Ordering

Lexicographic compare on the concatenation (x, z) interpreted as an unsigned-integer array, low-to-high word order.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<const W: usize> PartialEq for PauliString<W>

fn eq(&self, other: &PauliString<W>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<const W: usize> PartialOrd for PauliString<W>

fn partial_cmp(&self, other: &Self) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<const W: usize> Zeroable for PauliString<W>

fn zeroed() -> Self

Calls zeroed.

impl<const W: usize> Copy for PauliString<W>

impl<const W: usize> Eq for PauliString<W>

impl<const W: usize> Pod for PauliString<W>

impl<const W: usize> StructuralPartialEq for PauliString<W>