Struct VariationalCircuit 

pub struct VariationalCircuit {
    pub num_qubits: usize,
    pub num_params: usize,
    pub parameters: Array1<f64>,
    pub num_layers: usize,
    pub ansatz_type: AnsatzType,
}

Variational quantum circuit with parameterized gates

Fields

num_qubits: usize

Number of qubits

num_params: usize

Number of parameters

parameters: Array1<f64>

Current parameters

num_layers: usize

Number of layers

ansatz_type: AnsatzType

Type of ansatz

Implementations

impl VariationalCircuit

pub fn new( num_qubits: usize, num_params: usize, num_layers: usize, ansatz_type: AnsatzType, ) -> Result<Self>

Creates a new variational circuit

pub fn create_circuit<const N: usize>(&self) -> Result<Circuit<N>>

Creates a circuit with the current parameters

pub fn compute_expectation( &self, hamiltonian: &[(f64, Vec<(usize, usize)>)], ) -> Result<f64>

Computes the expectation value of a Hamiltonian via direct statevector simulation.

hamiltonian is a slice of (coefficient, pauli_term_list) tuples. Each pauli_term_list contains (qubit_index, pauli_type) pairs where pauli_type encodes 0=I, 1=X, 2=Y, 3=Z.

The ansatz consists of num_layers repetitions of: – H gate on every qubit – RZ(θ_i) on qubit i using the i-th parameter (cycling if parameters run out) – CNOT chain (linear nearest-neighbour entanglement)

Returns Σ_k coef_k · ⟨ψ | P_k | ψ⟩.

pub fn evaluate( &self, objective: &dyn Fn(&VariationalCircuit) -> Result<f64>, ) -> Result<f64>

Evaluates the objective function for optimization

pub fn optimize( &mut self, objective: &dyn Fn(&VariationalCircuit) -> Result<f64>, optimizer: &Optimizer, max_iterations: usize, ) -> Result<f64>

Optimizes the circuit parameters using the parameter-shift rule for gradient computation.

For each parameter θ_i the gradient is estimated as: ∂f/∂θ_i ≈ (f(θ_i + π/2) − f(θ_i − π/2)) / 2

A gradient-descent update is then applied with the learning rate from the supplied Optimizer. Other optimizer variants fall back to lr = 0.01.

Trait Implementations

impl Clone for VariationalCircuit

fn clone(&self) -> VariationalCircuit

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for VariationalCircuit

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

Formats the value using the given formatter.