U2.cpp

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/*
Created on Fri Jun 26 14:13:26 2020
Copyright 2020 Peter Rakyta, Ph.D.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

@author: Peter Rakyta, Ph.D.
*/
#include "U2.h"


U2::U2() {

    // A string labeling the gate operation
    name = "U2";

    // number of qubits spanning the matrix of the gate
    qbit_num = -1;
    // the size of the matrix
    matrix_size = -1;
    // A string describing the type of the gate
    type = U2_OPERATION;

    // The index of the qubit on which the gate acts (target_qbit >= 0)
    target_qbit = -1;
    // The index of the qubit which acts as a control qubit (control_qbit >= 0) in controlled gates
    control_qbit = -1;

    parameter_num = 0;

}


U2::U2(int qbit_num_in, int target_qbit_in) {
    
    // A string labeling the gate operation
    name = "U2";

    // number of qubits spanning the matrix of the gate
    qbit_num = qbit_num_in;
    // the size of the matrix
    matrix_size = Power_of_2(qbit_num);
    // A string describing the type of the gate
    type = U2_OPERATION;

    if (target_qbit_in >= qbit_num) {
        std::stringstream sstream;
        sstream << "The index of the target qubit is larger than the number of qubits" << std::endl;
    print(sstream, 0);        
        throw "The index of the target qubit is larger than the number of qubits";
    }
    
    // The index of the qubit on which the gate acts (target_qbit >= 0)
    target_qbit = target_qbit_in;
    // The index of the qubit which acts as a control qubit (control_qbit >= 0) in controlled gates
    control_qbit = -1;

    parameter_num = 2;

}


U2::~U2() {

}


void 
U2::apply_to( Matrix_real& parameters, Matrix& input, int parallel ) {

    if (input.rows != matrix_size ) {
        std::string err("U2::apply_to: Wrong input size in U2 gate apply.");
        throw err;    
    }


    double ThetaOver2, Phi, Lambda;

    Phi = parameters[0];
    Lambda = parameters[1];
    parameters_for_calc_one_qubit(ThetaOver2, Phi, Lambda);
  
    // get the U3 gate of one qubit
    Matrix u3_1qbit = calc_one_qubit_u3(ThetaOver2, Phi, Lambda );


    apply_kernel_to( u3_1qbit, input, false, parallel );


}


void 
U2::apply_from_right( Matrix_real& parameters, Matrix& input ) {

    if (input.cols != matrix_size ) {
        std::string err("U2::apply_from_right: Wrong matrix size in U2 apply_from_right.");
        throw err;    
    }


    double ThetaOver2, Phi, Lambda;

    Phi = parameters[0];
    Lambda = parameters[1];
    parameters_for_calc_one_qubit(ThetaOver2, Phi, Lambda);

    // get the U3 gate of one qubit
    Matrix u3_1qbit = calc_one_qubit_u3(ThetaOver2, Phi, Lambda );


    apply_kernel_from_right(u3_1qbit, input);


}


std::vector<Matrix> U2::apply_derivate_to( Matrix_real& parameters_mtx, Matrix& input, int parallel ) {

    if (input.rows != matrix_size ) {
        std::string err("U2::apply_derivate_to: Wrong matrix size in U2 gate apply.");
        throw err;    
    }


    std::vector<Matrix> ret;

    Matrix_real parameters_tmp(1,2);

    parameters_tmp[0] = parameters_mtx[0] + M_PI/2;
    parameters_tmp[1] = parameters_mtx[1];
    Matrix res_mtx_phi = input.copy();
    apply_to(parameters_tmp, res_mtx_phi, parallel);
    ret.push_back(res_mtx_phi);

    
    parameters_tmp[0] = parameters_mtx[0];
    parameters_tmp[1] = parameters_mtx[1] + M_PI/2;
    Matrix res_mtx_lambda = input.copy();
    apply_to(parameters_tmp, res_mtx_lambda, parallel);
    ret.push_back(res_mtx_lambda);
    

    
    return ret;


}


void 
U2::parameters_for_calc_one_qubit( double& ThetaOver2, double& Phi, double& Lambda){

    ThetaOver2 = M_PI/4;
    // Phi is passed through unchanged
    // Lambda is passed through unchanged

}


U2* U2::clone() {

    U2* ret = new U2(qbit_num, target_qbit);
    
    ret->set_parameter_start_idx( get_parameter_start_idx() );
    ret->set_parents( parents );
    ret->set_children( children );

    return ret;
}


Matrix_real 
U2::extract_parameters( Matrix_real& parameters ) {

    if ( get_parameter_start_idx() + get_parameter_num() > parameters.size()  ) {
        std::string err("U2::extract_parameters: Cant extract parameters, since the dinput arary has not enough elements.");
        throw err;     
    }

    Matrix_real extracted_parameters(1,2);

    extracted_parameters[0] = std::fmod( parameters[ get_parameter_start_idx() ], 2*M_PI);
    extracted_parameters[1] = std::fmod( parameters[ get_parameter_start_idx() + 1 ], 2*M_PI);

    return extracted_parameters;

}