Struct VqlsSolver 

pub struct VqlsSolver { /* private fields */ }

The VQLS optimiser: holds the operator A, the normalised target |b⟩, and the ansatz, and minimises the global cost over the ansatz parameters.

Implementations

impl VqlsSolver

pub fn new( operator: LcuOperator, b: &[Complex<f32>], ansatz: HardwareEfficientAnsatz, ) -> QuantumResult<Self>

Build a solver for A|x⟩ = |b⟩. b is normalised internally and must be non-zero with b.len() == 2^{n_qubits}.

Errors

• QuantumError::DimensionMismatch if b’s length or the ansatz qubit count disagree with the operator’s qubit count.
• QuantumError::InvalidParameter if b is the zero vector.

pub fn cost(&self, params: &[f32]) -> QuantumResult<f64>

Evaluate the global cost C(θ) = 1 − |⟨b|A|x⟩|² / ⟨x|A†A|x⟩ for a given parameter vector.

Errors

Propagates ansatz preparation errors.

pub fn solution_state(&self, params: &[f32]) -> QuantumResult<Vec<Complex<f32>>>

The normalised ansatz state |x(θ)⟩ for inspection.

Errors

Propagates ansatz preparation errors.

pub fn optimize( &self, init_params: &[f32], max_iters: usize, lr: f32, eps: f32, tol: f64, ) -> QuantumResult<VqlsResult>

Minimise the cost by finite-difference gradient descent.

Starts from init_params, runs up to max_iters iterations with central difference step eps and an initial learning rate lr that is halved (backtracking) whenever a step fails to decrease the cost. Stops early when the cost drops below tol or the learning rate underflows.

Errors

• QuantumError::DimensionMismatch if init_params.len() != n_params().
• Propagates cost-evaluation errors.

Trait Implementations

impl Clone for VqlsSolver

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for VqlsSolver

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

Formats the value using the given formatter.