U3.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 "U3.h"
#include "tbb/tbb.h"

// pi/2
static double M_PIOver2 = M_PI/2;

//static tbb::spin_mutex my_mutex;
U3::U3() {

    // A string labeling the gate operation
    name = "U3";

    // 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 = U3_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;

}

U3::U3(int qbit_num_in, int target_qbit_in) {
    
    // A string labeling the gate operation
    name = "U3";

    // 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 = U3_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 = 3;

}


U3::~U3() {

}


Matrix
U3::get_matrix( Matrix_real& parameters ) {
        
        return get_matrix( parameters, false );
}


Matrix
U3::get_matrix( Matrix_real& parameters, int parallel ) {

        Matrix U3_matrix = create_identity(matrix_size);
        apply_to(parameters, U3_matrix, parallel);

#ifdef DEBUG
        if (U3_matrix.isnan()) {
            std::stringstream sstream;
         sstream << "U3::get_matrix: U3_matrix contains NaN." << std::endl;
         verbose_level=1;
            print(sstream,verbose_level);      
        }
#endif

        return U3_matrix;

}


void 
U3::apply_to_list( Matrix_real& parameters_mtx, std::vector<Matrix>& inputs, int parallel ) {

    int work_batch = 1;
    if ( parallel == 0 ) {
        work_batch = inputs.size();
    }
    else {
        work_batch = 1;
    }


    tbb::parallel_for( tbb::blocked_range<int>(0,inputs.size(),work_batch), [&](tbb::blocked_range<int> r) {
        for (int idx=r.begin(); idx<r.end(); ++idx) { 

            Matrix* input = &inputs[idx];

            apply_to( parameters_mtx, *input, parallel );

        }

    });

}


void 
U3::apply_to( Matrix_real& parameters_mtx, Matrix& input, int parallel ) {
    
    if (input.rows != matrix_size ) {
        std::string err("U3::apply_to: Wrong input size in U3 gate apply.");
        throw err;    
    }

    double ThetaOver2 = parameters_mtx[0];
    double Phi = parameters_mtx[1];
    double Lambda = parameters_mtx[2];

    // 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 
U3::apply_from_right( Matrix_real& parameters_mtx, Matrix& input ) {
    
    if (input.cols != matrix_size ) {
        std::string err("U3::apply_from_right: Wrong matrix size in U3 apply_from_right.");
        throw err;    
    }

    double ThetaOver2 = parameters_mtx[0];
    double Phi = parameters_mtx[1];
    double Lambda = parameters_mtx[2];

    // 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> 
U3::apply_derivate_to( Matrix_real& parameters_mtx, Matrix& input, int parallel ) {
    
    if (input.rows != matrix_size ) {
        std::string err("U3::apply_derivate_to: Wrong matrix size in U3 gate apply.");
        throw err;    
    }

    std::vector<Matrix> ret;

    double ThetaOver2 = parameters_mtx[0];
    double Phi = parameters_mtx[1];
    double Lambda = parameters_mtx[2];
    bool deriv = true;


    Matrix u3_1qbit_theta = calc_one_qubit_u3(ThetaOver2+M_PIOver2, Phi, Lambda);
    Matrix res_mtx_theta = input.copy();
    apply_kernel_to( u3_1qbit_theta, res_mtx_theta, deriv, parallel );
    ret.push_back(res_mtx_theta);


    Matrix u3_1qbit_phi = calc_one_qubit_u3(ThetaOver2, Phi+M_PIOver2, Lambda );
    memset(u3_1qbit_phi.get_data(), 0.0, 2*sizeof(QGD_Complex16) );
    Matrix res_mtx_phi = input.copy();
    apply_kernel_to( u3_1qbit_phi, res_mtx_phi, deriv, parallel );
    ret.push_back(res_mtx_phi);


    Matrix u3_1qbit_lambda = calc_one_qubit_u3(ThetaOver2, Phi, Lambda+M_PIOver2 );
    memset(u3_1qbit_lambda.get_data(), 0.0, sizeof(QGD_Complex16) );
    memset(u3_1qbit_lambda.get_data()+2, 0.0, sizeof(QGD_Complex16) );
    Matrix res_mtx_lambda = input.copy();
    apply_kernel_to( u3_1qbit_lambda, res_mtx_lambda, deriv, parallel );
    ret.push_back(res_mtx_lambda);


    return ret;
}

void U3::set_qbit_num(int qbit_num_in) {
    Gate::set_qbit_num(qbit_num_in); // setting the number of qubits
}

void U3::reorder_qubits( std::vector<int> qbit_list) {
    Gate::reorder_qubits(qbit_list);
}

U3* U3::clone() {

    U3* ret = new U3(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 
U3::extract_parameters( Matrix_real& parameters ) {

    if ( get_parameter_start_idx() + get_parameter_num() > parameters.size()  ) {
        std::string err("U3::extract_parameters: Cant extract parameters, since the dinput arary has not enough elements.");
        throw err;     
    }

    Matrix_real extracted_parameters(1, 3);

    extracted_parameters[0] = std::fmod( 2*parameters[ get_parameter_start_idx() ], 4*M_PI);
    extracted_parameters[1] = std::fmod( parameters[ get_parameter_start_idx()+1 ], 2*M_PI);
    extracted_parameters[2] = std::fmod( parameters[ get_parameter_start_idx()+2 ], 2*M_PI);

    return extracted_parameters;
}