RXX.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 "RXX.h"
#include "gate_kernel_templates.h"
using namespace std;

// Build the 4x4 RXX kernel matrix for either float32 or float64 precision.
RXX::RXX() : Gate() {

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

    // A string describing the type of the gate
    type = RXX_OPERATION;

    // Initialize target qubits vector (empty for nullary constructor)
    target_qbits.clear();

    parameter_num = 1;
}

RXX::RXX(int qbit_num_in, const std::vector<int>& target_qbits_in)
    : Gate(qbit_num_in, target_qbits_in) {

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

    // A string describing the type of the gate
    type = RXX_OPERATION;

    // Validate that we have exactly 2 target qubits
    if (target_qbits_in.size() != 2) {
        std::stringstream sstream;
        sstream << "RXX gate requires exactly 2 target qubits, got " << target_qbits_in.size() << std::endl;
        print(sstream, 0);
        throw sstream.str();
    }

    // Check that target qubits are unique
    if (target_qbits_in[0] == target_qbits_in[1]) {
        std::stringstream sstream;
        sstream << "The two target qubits cannot be the same" << std::endl;
        print(sstream, 0);
        throw sstream.str();
    }

    parameter_num = 1;
}

RXX::~RXX() {

}

Matrix RXX::gate_kernel(const Matrix_real& precomputed_sincos) {
    Matrix ret;
    gate_kernel_to(precomputed_sincos, ret);
    return ret;
}

Matrix_float RXX::gate_kernel(const Matrix_real_float& precomputed_sincos) {
    Matrix_float ret;
    gate_kernel_to(precomputed_sincos, ret);
    return ret;
}

Matrix RXX::inverse_gate_kernel(const Matrix_real& precomputed_sincos) {
    Matrix ret;
    inverse_gate_kernel_to(precomputed_sincos, ret);
    return ret;
}

Matrix_float RXX::inverse_gate_kernel(const Matrix_real_float& precomputed_sincos) {
    Matrix_float ret;
    inverse_gate_kernel_to(precomputed_sincos, ret);
    return ret;
}

Matrix RXX::derivative_kernel(const Matrix_real& precomputed_sincos, int param_idx) {
    Matrix ret;
    derivative_kernel_to(precomputed_sincos, param_idx, ret);
    return ret;
}

Matrix_float RXX::derivative_kernel(const Matrix_real_float& precomputed_sincos, int param_idx) {
    Matrix_float ret;
    derivative_kernel_to(precomputed_sincos, param_idx, ret);
    return ret;
}

void RXX::gate_kernel_to(const Matrix_real& precomputed_sincos, Matrix& output) {
    const int theta_offset = 0 * precomputed_sincos.stride;
    const double s_theta = precomputed_sincos[theta_offset + 0];
    const double c_theta = precomputed_sincos[theta_offset + 1];
    build_rxx_kernel_from_trig_to<Matrix, double>(output, s_theta, c_theta);
}

void RXX::gate_kernel_to(const Matrix_real_float& precomputed_sincos, Matrix_float& output) {
    const int theta_offset = 0 * precomputed_sincos.stride;
    const float s_theta = precomputed_sincos[theta_offset + 0];
    const float c_theta = precomputed_sincos[theta_offset + 1];
    build_rxx_kernel_from_trig_to<Matrix_float, float>(output, s_theta, c_theta);
}

void RXX::inverse_gate_kernel_to(const Matrix_real& precomputed_sincos, Matrix& output) {
    const int theta_offset = 0 * precomputed_sincos.stride;
    const double s_theta = precomputed_sincos[theta_offset + 0];
    const double c_theta = precomputed_sincos[theta_offset + 1];
    build_rxx_kernel_from_trig_to<Matrix, double>(output, -s_theta, c_theta);
}

void RXX::inverse_gate_kernel_to(const Matrix_real_float& precomputed_sincos, Matrix_float& output) {
    const int theta_offset = 0 * precomputed_sincos.stride;
    const float s_theta = precomputed_sincos[theta_offset + 0];
    const float c_theta = precomputed_sincos[theta_offset + 1];
    build_rxx_kernel_from_trig_to<Matrix_float, float>(output, -s_theta, c_theta);
}

void RXX::derivative_kernel_to(const Matrix_real& precomputed_sincos, int param_idx, Matrix& output) {
    if (param_idx != 0) {
        output = Matrix();
        return;
    }
    const int theta_offset = 0 * precomputed_sincos.stride;
    const double s_theta = precomputed_sincos[theta_offset + 0];
    const double c_theta = precomputed_sincos[theta_offset + 1];
    build_rxx_derivative_kernel_from_trig_to<Matrix, double>(output, s_theta, c_theta);
}

void RXX::derivative_kernel_to(const Matrix_real_float& precomputed_sincos, int param_idx, Matrix_float& output) {
    if (param_idx != 0) {
        output = Matrix_float();
        return;
    }
    const int theta_offset = 0 * precomputed_sincos.stride;
    const float s_theta = precomputed_sincos[theta_offset + 0];
    const float c_theta = precomputed_sincos[theta_offset + 1];
    build_rxx_derivative_kernel_from_trig_to<Matrix_float, float>(output, s_theta, c_theta);
}

RXX* RXX::clone() {

    RXX* ret = new RXX(qbit_num, target_qbits);

    ret->set_parameter_start_idx(get_parameter_start_idx());
    ret->set_parents(parents);
    ret->set_children(children);

    return ret;
}

std::vector<double>
RXX::get_parameter_multipliers() const {
    return {2.0};
}