Struct QubitRegister 

pub struct QubitRegister { /* private fields */ }

An n-qubit quantum register stored as a 2^n-dimensional statevector.

The state is always kept normalised. Amplitudes are ordered by the binary representation of the basis index with qubit 0 as the least-significant bit.

Implementations

impl QubitRegister

pub fn new( n_qubits: usize, amplitudes: Vec<Complex<f64>>, ) -> QuantumResult<Self>

Create a register from a raw amplitude vector.

n_qubits must satisfy amplitudes.len() == 2^n_qubits. The vector is automatically re-normalised.

pub fn from_qubit(q: &Qubit) -> Self

Wrap a single Qubit as a 1-qubit register.

pub fn new_zero_state(n_qubits: usize) -> QuantumResult<Self>

All-zeros state |0…0⟩.

pub fn new_uniform_superposition(n_qubits: usize) -> QuantumResult<Self>

Equal superposition (Hadamard applied to all qubits of |0…0⟩).

Each amplitude has magnitude 1/√(2^n).

pub fn new_basis_state(n_qubits: usize, k: usize) -> QuantumResult<Self>

Computational basis state |k⟩ for a given integer k < 2^n.

pub fn n_qubits(&self) -> usize

Number of qubits in this register.

pub fn dim(&self) -> usize

Hilbert-space dimension: 2^n.

pub fn amplitudes(&self) -> &[Complex<f64>]

Slice over all amplitudes.

pub fn amplitudes_mut(&mut self) -> &mut Vec<Complex<f64>>

Mutable slice over all amplitudes (use with care — normalisation is not automatically maintained).

pub fn amplitude(&self, k: usize) -> QuantumResult<Complex<f64>>

Amplitude for basis state k.

pub fn probability(&self, k: usize) -> QuantumResult<f64>

Probability of measuring basis state k.

pub fn probabilities(&self) -> Vec<f64>

All measurement probabilities |ψ_k|² in basis order.

pub fn normalise(&mut self) -> QuantumResult<()>

Re-normalise the statevector in place.

pub fn is_normalised(&self, tol: f64) -> bool

Check that the statevector is normalised within tol.

pub fn tensor_product(a: &QubitRegister, b: &QubitRegister) -> QubitRegister

Tensor product (Kronecker product) of two registers: result = a ⊗ b.

If a has n₁ qubits and b has n₂ qubits, the result has n₁+n₂ qubits. Qubit ordering: qubits of a are the more significant bits.

pub fn measure_qubit<R: Rng>( &self, qubit_idx: usize, rng: &mut R, ) -> QuantumResult<(u8, QubitRegister)>

Measure a single qubit at index qubit_idx and return (outcome, collapsed_state).

The returned register has the same number of qubits; amplitudes inconsistent with the measurement outcome are zeroed and the result is renormalised.

pub fn measure_all<R: Rng>(&self, rng: &mut R) -> Vec<u8>

Measure all qubits and return a bit-string outcome (qubit 0 first).

Samples once from the Born-rule distribution.

pub fn inner_product( &self, other: &QubitRegister, ) -> QuantumResult<Complex<f64>>

Inner product ⟨other|self⟩.

pub fn fidelity(&self, other: &QubitRegister) -> QuantumResult<f64>

Fidelity |⟨other|self⟩|² with another register.

pub fn entropy(&self) -> f64

Von-Neumann entropy (in nats) of the full pure state (always 0 for pure states). Provided for completeness; useful as a sanity-check (should return 0.0).

Trait Implementations

impl Clone for QubitRegister

fn clone(&self) -> QubitRegister

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for QubitRegister

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

Formats the value using the given formatter.

impl Default for QubitRegister

fn default() -> Self

Returns the “default value” for a type.

impl Display for QubitRegister

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

Formats the value using the given formatter.

impl PartialEq for QubitRegister

fn eq(&self, other: &QubitRegister) -> bool

Equality operator ==.

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

Inequality operator !=.

impl StructuralPartialEq for QubitRegister