{
  "cells": [
    {
      "cell_type": "markdown",
      "id": "b6d1e3ec",
      "metadata": {},
      "source": [
        "---\n",
        "title: \"Modelo de Ising de campo transversal con gestión del rendimiento de Q-CTRL\"\n",
        "description: \"Construye y resuelve el modelo de Ising de campo transversal utilizando Fire Opal y Qiskit\"\n",
        "---\n",
        "\n",
        "{/* cspell:ignore fontsize sharey rmse RMSE boxstyle */}\n",
        "\n",
        "<span id=\"transverse-field-ising-model-with-q-ctrls-performance-management\" />\n",
        "\n",
        "# Modelo de Ising de campo transversal con gestión del rendimiento de Q-CTRL\n",
        "\n"
      ]
    },
    {
      "attachments": {},
      "cell_type": "markdown",
      "id": "a6f69b77",
      "metadata": {},
      "source": [
        "*Estimación de uso: 2 minutos en un procesador Heron r2. (NOTA: Esto es sólo una estimación. Su tiempo de ejecución puede variar)*\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "8bf80006",
      "metadata": {},
      "source": [
        "<span id=\"background\" />\n",
        "\n",
        "## En segundo plano\n",
        "\n",
        "El modelo de Ising de campo transversal (TFIM) es importante para estudiar el magnetismo cuántico y las transiciones de fase. Describe un conjunto de espines dispuestos en un entramado, donde cada espín interactúa con sus vecinos a la vez que recibe la influencia de un campo magnético externo que impulsa las fluctuaciones cuánticas.\n",
        "\n",
        "Un enfoque común para simular este modelo es utilizar la descomposición de Trotter para aproximar el operador de evolución temporal, construyendo circuitos que alternan entre rotaciones de un solo qubit e interacciones de dos qubits enredados. Sin embargo, esta simulación en hardware real es un reto debido al ruido y la decoherencia, que provocan desviaciones de la dinámica real. Para superar esto, utilizamos las herramientas de gestión de rendimiento y supresión de errores Fire Opal de Q-CTRL, ofrecidas como una función Qiskit (consulte la [documentación de Fire Opal](/docs/guides/q-ctrl-performance-management) ). Fire Opal optimiza automáticamente la ejecución del circuito aplicando técnicas de desacoplamiento dinámico, diseño avanzado, enrutamiento y otras técnicas de supresión de errores, todas ellas encaminadas a reducir el ruido. Con estas mejoras, los resultados del hardware se ajustan más a las simulaciones sin ruido y, por tanto, podemos estudiar la dinámica de magnetización del TFIM con mayor fidelidad.\n",
        "\n",
        "En este tutorial vamos a:\n",
        "\n",
        "* Construir el Hamiltoniano TFIM en un gráfico de triángulos de espín conectados\n",
        "* Simular la evolución temporal con circuitos trotterizados a diferentes profundidades\n",
        "* Calcular y visualizar las magnetizaciones de un solo qubit $\\langle Z_i \\rangle$ a lo largo del tiempo\n",
        "* Comparar simulaciones de referencia con resultados de ejecuciones de hardware mediante la gestión del rendimiento Fire Opal de Q-CTRL\n",
        "\n",
        "<span id=\"overview\" />\n",
        "\n",
        "## Visión general\n",
        "\n",
        "El modelo de Ising de campo transversal (TFIM) es un modelo cuántico de espín que capta características esenciales de las transiciones cuánticas de fase. El Hamiltoniano se define como:\n",
        "\n",
        "$$\n",
        "H = -J \\sum_{i} Z_i Z_{i+1} - h \\sum_{i} X_i\n",
        "$$\n",
        "\n",
        "donde $Z_i$ y $X_i$ son operadores de Pauli que actúan sobre el qubit $i$, $J$ es la fuerza de acoplamiento entre espines vecinos, y $h$ es la fuerza del campo magnético transversal. El primer término representa las interacciones ferromagnéticas clásicas, mientras que el segundo introduce fluctuaciones cuánticas a través del campo transversal. Para simular la dinámica TFIM, se utiliza una descomposición Trotter del operador unitario de evolución $e^{-iHt}$, implementado a través de capas de puertas RX y RZZ basadas en un gráfico personalizado de triángulos de espín conectados. La simulación explora cómo evoluciona la magnetización $\\langle Z \\rangle$ al aumentar los pasos de Trotter.\n",
        "\n",
        "El rendimiento de la implementación TFIM propuesta se evalúa comparando simulaciones sin ruido con backends ruidosos. Las funciones mejoradas de ejecución y supresión de errores de Fire Opal se utilizan para mitigar el efecto del ruido en el hardware real, con lo que se obtienen estimaciones más fiables de observables de espín como $\\langle Z_i \\rangle$ y correladores $\\langle Z_i Z_j \\rangle$.\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "55b94021",
      "metadata": {},
      "source": [
        "<span id=\"requirements\" />\n",
        "\n",
        "## Requisitos\n",
        "\n",
        "Antes de empezar este tutorial, asegúrate de tener instalado lo siguiente:\n",
        "\n",
        "* Qiskit SDK v1.4 o posterior, con soporte [de visualización](/docs/api/qiskit/visualization)\n",
        "* Qiskit Runtime v0.40 o posterior (`pip install qiskit-ibm-runtime`)\n",
        "* Qiskit Functions Catalog v0.9.0 (`pip install qiskit-ibm-catalog`)\n",
        "* Fire Opal SDK v9.0.2 o posterior (`pip install fire-opal`)\n",
        "* Q-CTRL Visualizer v8.0.2 o posterior (`pip install qctrl-visualizer`)\n",
        "\n"
      ]
    },
    {
      "attachments": {},
      "cell_type": "markdown",
      "id": "7db2e559",
      "metadata": {},
      "source": [
        "<span id=\"setup\" />\n",
        "\n",
        "## Configuración\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "ecaa518f",
      "metadata": {},
      "source": [
        "Primero, autentíquese utilizando su [clave API IBM Quantum](http://quantum.cloud.ibm.com/). A continuación, selecciona la función de Qiskit de la siguiente manera. (Este código da por hecho que ya has [guardado tu cuenta](/docs/guides/functions-get-started#install-qiskit-functions-catalog-client) en tu entorno local.)\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 6,
      "id": "bc380c46",
      "metadata": {},
      "outputs": [],
      "source": [
        "from qiskit.transpiler.preset_passmanagers import generate_preset_pass_manager\n",
        "from qiskit import QuantumCircuit\n",
        "from qiskit_ibm_catalog import QiskitFunctionsCatalog\n",
        "from qiskit_ibm_runtime import QiskitRuntimeService\n",
        "from qiskit_ibm_runtime import SamplerV2 as Sampler\n",
        "from qiskit.quantum_info import SparsePauliOp\n",
        "from qiskit_aer import AerSimulator\n",
        "\n",
        "import numpy as np\n",
        "import networkx as nx\n",
        "import matplotlib.pyplot as plt\n",
        "import qctrlvisualizer as qv"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "id": "e9d916b6",
      "metadata": {},
      "outputs": [],
      "source": [
        "catalog = QiskitFunctionsCatalog(channel=\"ibm_quantum_platform\")\n",
        "\n",
        "# Access Function\n",
        "perf_mgmt = catalog.load(\"q-ctrl/performance-management\")"
      ]
    },
    {
      "attachments": {},
      "cell_type": "markdown",
      "id": "988ee237",
      "metadata": {},
      "source": [
        "<span id=\"step-1-map-classical-inputs-to-a-quantum-problem\" />\n",
        "\n",
        "## Paso 1: Asignar entradas clásicas a un problema cuántico\n",
        "\n",
        "<span id=\"generate-tfim-graph\" />\n",
        "\n",
        "### Generar gráfico TFIM\n",
        "\n",
        "Comenzamos definiendo la red de espines y los acoplamientos entre ellos. En este tutorial, la celosía se construye a partir de triángulos conectados dispuestos en una cadena lineal. Cada triángulo consta de tres nodos conectados en un bucle cerrado, y la cadena se forma uniendo un nodo de cada triángulo al triángulo anterior.\n",
        "\n",
        "La función de ayuda `connected_triangles_adj_matrix` construye la matriz de adyacencia para esta estructura. Para una cadena de triángulos $n$, el gráfico resultante contiene $2n+1$ nodos.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 7,
      "id": "829f1b6d",
      "metadata": {},
      "outputs": [],
      "source": [
        "def connected_triangles_adj_matrix(n):\n",
        "    \"\"\"\n",
        "    Generate the adjacency matrix for 'n' connected triangles in a chain.\n",
        "    \"\"\"\n",
        "    num_nodes = 2 * n + 1\n",
        "    adj_matrix = np.zeros((num_nodes, num_nodes), dtype=int)\n",
        "\n",
        "    for i in range(n):\n",
        "        a, b, c = i * 2, i * 2 + 1, i * 2 + 2  # Nodes of the current triangle\n",
        "\n",
        "        # Connect the three nodes in a triangle\n",
        "        adj_matrix[a, b] = adj_matrix[b, a] = 1\n",
        "        adj_matrix[b, c] = adj_matrix[c, b] = 1\n",
        "        adj_matrix[a, c] = adj_matrix[c, a] = 1\n",
        "\n",
        "        # If not the first triangle, connect to the previous triangle\n",
        "        if i > 0:\n",
        "            adj_matrix[a, a - 1] = adj_matrix[a - 1, a] = 1\n",
        "\n",
        "    return adj_matrix"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "53869b13",
      "metadata": {},
      "source": [
        "Para visualizar la red que acabamos de definir, podemos trazar la cadena de triángulos conectados y etiquetar cada nodo. La siguiente función construye el gráfico para un número determinado de triángulos y lo muestra.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 8,
      "id": "2fc293aa",
      "metadata": {},
      "outputs": [],
      "source": [
        "def plot_triangle_chain(n, side=1.0):\n",
        "    \"\"\"\n",
        "    Plot a horizontal chain of n equilateral triangles.\n",
        "    Baseline: even nodes (0,2,4,...,2n) on y=0\n",
        "    Apexes: odd nodes (1,3,5,...,2n-1) above the midpoint.\n",
        "    \"\"\"\n",
        "    # Build graph\n",
        "    A = connected_triangles_adj_matrix(n)\n",
        "    G = nx.from_numpy_array(A)\n",
        "\n",
        "    h = np.sqrt(3) / 2 * side\n",
        "    pos = {}\n",
        "\n",
        "    # Place baseline nodes\n",
        "    for k in range(n + 1):\n",
        "        pos[2 * k] = (k * side, 0.0)\n",
        "\n",
        "    # Place apex nodes\n",
        "    for k in range(n):\n",
        "        x_left = pos[2 * k][0]\n",
        "        x_right = pos[2 * k + 2][0]\n",
        "        pos[2 * k + 1] = ((x_left + x_right) / 2, h)\n",
        "\n",
        "    # Draw\n",
        "    fig, ax = plt.subplots(figsize=(1.5 * n, 2.5))\n",
        "    nx.draw(\n",
        "        G,\n",
        "        pos,\n",
        "        ax=ax,\n",
        "        with_labels=True,\n",
        "        font_size=10,\n",
        "        font_color=\"white\",\n",
        "        node_size=600,\n",
        "        node_color=qv.QCTRL_STYLE_COLORS[0],\n",
        "        edge_color=\"black\",\n",
        "        width=2,\n",
        "    )\n",
        "    ax.set_aspect(\"equal\")\n",
        "    ax.margins(0.2)\n",
        "    plt.show()\n",
        "\n",
        "    return G, pos"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "8abc0622",
      "metadata": {},
      "source": [
        "Para este tutorial utilizaremos una cadena de 20 triángulos.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 9,
      "id": "861ab6e3",
      "metadata": {},
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<Image src=\"/docs/images/tutorials/transverse-field-ising-model/extracted-outputs/861ab6e3-0.avif\" alt=\"Output of the previous code cell\" />"
            ]
          },
          "metadata": {},
          "output_type": "display_data"
        }
      ],
      "source": [
        "n_triangles = 20\n",
        "n_qubits = 2 * n_triangles + 1\n",
        "plot_triangle_chain(n_triangles, side=1.0)\n",
        "plt.show()"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "ac6f36e3",
      "metadata": {},
      "source": [
        "<span id=\"coloring-graph-edges\" />\n",
        "\n",
        "### Colorear los bordes de los gráficos\n",
        "\n",
        "Para implementar el acoplamiento espín-espín, es útil agrupar aristas que no se solapen. Esto nos permite aplicar puertas de dos qubits en paralelo. Podemos hacerlo con un sencillo procedimiento de coloración de aristas [\\[1\\]](#references), que asigna un color a cada arista para que las aristas que se encuentran en el mismo nodo se coloquen en grupos diferentes.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "id": "c893b88f",
      "metadata": {},
      "outputs": [],
      "source": [
        "def edge_coloring(graph):\n",
        "    \"\"\"\n",
        "    Takes a NetworkX graph and returns a list of lists\n",
        "    where each inner list contains\n",
        "    the edges assigned the same color.\n",
        "    \"\"\"\n",
        "    line_graph = nx.line_graph(graph)\n",
        "    edge_colors = nx.coloring.greedy_color(line_graph)\n",
        "\n",
        "    color_groups = {}\n",
        "    for edge, color in edge_colors.items():\n",
        "        if color not in color_groups:\n",
        "            color_groups[color] = []\n",
        "        color_groups[color].append(edge)\n",
        "\n",
        "    return list(color_groups.values())"
      ]
    },
    {
      "attachments": {},
      "cell_type": "markdown",
      "id": "b4d480b3",
      "metadata": {},
      "source": [
        "<span id=\"step-2-optimize-problem-for-quantum-hardware-execution\" />\n",
        "\n",
        "## Paso 2: Optimizar el problema para la ejecución en hardware cuántico\n",
        "\n",
        "<span id=\"generate-trotterized-circuits-on-spin-graphs\" />\n",
        "\n",
        "### Generar circuitos trotterizados en grafos de espín\n",
        "\n",
        "Para simular la dinámica del TFIM, construimos circuitos que aproximan el operador de evolución temporal.\n",
        "\n",
        "$$\n",
        "U(t) = e^{-i H t}, \\quad \\text{where} \\quad H = -J \\sum_{\\langle i,j \\rangle} Z_i Z_j - h \\sum_i X_i .\n",
        "$$\n",
        "\n",
        "Utilizamos una descomposición de Trotter de segundo orden:\n",
        "\n",
        "$$\n",
        "e^{-i H \\Delta t} \\approx e^{-i H_X \\Delta t / 2}\\, e^{-i H_Z \\Delta t}\\, e^{-i H_X \\Delta t / 2},\n",
        "$$\n",
        "\n",
        "donde $H_X = -h \\sum_i X_i$ y $H_Z = -J \\sum_{\\langle i,j \\rangle} Z_i Z_j$.\n",
        "\n",
        "* El término $H_X$ se implementa con capas de rotaciones `RX` .\n",
        "* El término $H_Z$ se implementa con capas de puertas `RZZ` a lo largo de las aristas del grafo de interacción.\n",
        "\n",
        "Los ángulos de estas puertas están determinados por el campo transversal $h$, la constante de acoplamiento $J$, y el paso de tiempo $\\Delta t$. Apilando múltiples pasos de Trotter, generamos circuitos de profundidad creciente que aproximan la dinámica del sistema. Las funciones `generate_tfim_circ_custom_graph` y `trotter_circuits` construyen un circuito cuántico trotterizado a partir de un grafo de interacción de espín arbitrario.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "id": "ebe5c712",
      "metadata": {},
      "outputs": [],
      "source": [
        "def generate_tfim_circ_custom_graph(\n",
        "    steps, h, J, dt, psi0, graph: nx.graph.Graph, meas_basis=\"Z\", mirror=False\n",
        "):\n",
        "    \"\"\"\n",
        "    Generate a second order trotter of the form e^(a+b) ~ e^(b/2) e^a e^(b/2)\n",
        "    for simulating a transverse field ising model:\n",
        "    e^{-i H t} where the Hamiltonian H = -J \\\\sum_i Z_i Z_{i+1} + h \\\\sum_i X_i.\n",
        "\n",
        "    steps: Number of trotter steps\n",
        "    theta_x: Angle for layer of X rotations\n",
        "    theta_zz: Angle for layer of ZZ rotations\n",
        "    theta_x: Angle for second layer of X rotations\n",
        "    J: Coupling between nearest neighbor spins\n",
        "    h: The transverse magnetic field strength\n",
        "    dt: t/total_steps\n",
        "    psi0: initial state (assumed to be prepared in the computational basis).\n",
        "    meas_basis: basis to measure all correlators in\n",
        "\n",
        "    This is a second order trotter of the form e^(a+b) ~ e^(b/2) e^a e^(b/2)\n",
        "    \"\"\"\n",
        "    theta_x = h * dt\n",
        "    theta_zz = -2 * J * dt\n",
        "    nq = graph.number_of_nodes()\n",
        "    color_edges = edge_coloring(graph)\n",
        "    circ = QuantumCircuit(nq, nq)\n",
        "    # Initial state, for typical cases in the computational basis\n",
        "    for i, b in enumerate(psi0):\n",
        "        if b == \"1\":\n",
        "            circ.x(i)\n",
        "    # Trotter steps\n",
        "    for step in range(steps):\n",
        "        for i in range(nq):\n",
        "            circ.rx(theta_x, i)\n",
        "        if mirror:\n",
        "            color_edges = [sublist[::-1] for sublist in color_edges[::-1]]\n",
        "        for edge_list in color_edges:\n",
        "            for edge in edge_list:\n",
        "                circ.rzz(theta_zz, edge[0], edge[1])\n",
        "        for i in range(nq):\n",
        "            circ.rx(theta_x, i)\n",
        "\n",
        "    # some typically used basis rotations\n",
        "    if meas_basis == \"X\":\n",
        "        for b in range(nq):\n",
        "            circ.h(b)\n",
        "    elif meas_basis == \"Y\":\n",
        "        for b in range(nq):\n",
        "            circ.sdg(b)\n",
        "            circ.h(b)\n",
        "\n",
        "    for i in range(nq):\n",
        "        circ.measure(i, i)\n",
        "\n",
        "    return circ\n",
        "\n",
        "\n",
        "def trotter_circuits(G, d_ind_tot, J, h, dt, meas_basis, mirror=True):\n",
        "    \"\"\"\n",
        "    Generates a sequence of Trotterized circuits, each with increasing depth.\n",
        "    Given a spin interaction graph and Hamiltonian parameters, it constructs\n",
        "    a list of circuits with 1 to d_ind_tot Trotter steps\n",
        "\n",
        "    G: Graph defining spin interactions (edges = ZZ couplings)\n",
        "    d_ind_tot: Number of Trotter steps (maximum depth)\n",
        "    J: Coupling between nearest neighboring spins\n",
        "    h: Transverse magnetic field strength\n",
        "    dt: (t / total_steps\n",
        "    meas_basis: Basis to measure all correlators in\n",
        "    mirror: If True, mirror the Trotter layers\n",
        "    \"\"\"\n",
        "    qubit_count = len(G)\n",
        "    circuits = []\n",
        "    psi0 = \"0\" * qubit_count\n",
        "\n",
        "    for steps in range(1, d_ind_tot + 1):\n",
        "        circuits.append(\n",
        "            generate_tfim_circ_custom_graph(\n",
        "                steps, h, J, dt, psi0, G, meas_basis, mirror\n",
        "            )\n",
        "        )\n",
        "    return circuits"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "50b94af2",
      "metadata": {},
      "source": [
        "<span id=\"estimate-single-qubit-magnetizations-$langle-z_i-rangle$\" />\n",
        "\n",
        "### Estimación de magnetizaciones de un solo qubit $\\langle Z_i \\rangle$\n",
        "\n",
        "Para estudiar la dinámica del modelo, queremos medir la magnetización de cada qubit, definida por el valor de expectativa $\\langle Z_i \\rangle = \\langle \\psi | Z_i | \\psi \\rangle$.\n",
        "\n",
        "En las simulaciones, podemos calcularlo directamente a partir de los resultados de las mediciones. La función `z_expectation` procesa los recuentos de la cadena de bits y devuelve el valor de $\\langle Z_i \\rangle$ para un índice de qubit elegido. En hardware real, evaluamos la misma cantidad especificando el operador de Pauli mediante la función `generate_z_observables`, y luego el backend calcula el valor de la expectativa.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "id": "3fc929e0",
      "metadata": {},
      "outputs": [],
      "source": [
        "def z_expectation(counts, index):\n",
        "    \"\"\"\n",
        "    counts: Dict of mitigated bitstrings.\n",
        "    index: Index i in the single operator expectation value < II...Z_i...I >\n",
        "        to be calculated.\n",
        "    return:  < Z_i >\n",
        "    \"\"\"\n",
        "    z_exp = 0\n",
        "    tot = 0\n",
        "    for bitstring, value in counts.items():\n",
        "        bit = int(bitstring[index])\n",
        "        sign = 1\n",
        "        if bit % 2 == 1:\n",
        "            sign = -1\n",
        "        z_exp += sign * value\n",
        "        tot += value\n",
        "\n",
        "    return z_exp / tot"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 13,
      "id": "c9e79716",
      "metadata": {},
      "outputs": [],
      "source": [
        "def generate_z_observables(nq):\n",
        "    observables = []\n",
        "    for i in range(nq):\n",
        "        pauli_string = \"\".join([\"Z\" if j == i else \"I\" for j in range(nq)])\n",
        "        observables.append(SparsePauliOp(pauli_string))\n",
        "    return observables"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 14,
      "id": "598d11cf",
      "metadata": {},
      "outputs": [],
      "source": [
        "observables = generate_z_observables(n_qubits)"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "397d9b05",
      "metadata": {},
      "source": [
        "A continuación definimos los parámetros para generar los circuitos trotterizados. En este tutorial, la red es una cadena de 20 triángulos conectados, lo que corresponde a un sistema de 41 qubits.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 15,
      "id": "2853d21b",
      "metadata": {},
      "outputs": [],
      "source": [
        "all_circs_mirror = []\n",
        "for num_triangles in [n_triangles]:\n",
        "    for meas_basis in [\"Z\"]:\n",
        "        A = connected_triangles_adj_matrix(num_triangles)\n",
        "        G = nx.from_numpy_array(A)\n",
        "        nq = len(G)\n",
        "        d_ind_tot = 22\n",
        "        dt = 2 * np.pi * 1 / 30 * 0.25\n",
        "        J = 1\n",
        "        h = -7\n",
        "        all_circs_mirror.extend(\n",
        "            trotter_circuits(G, d_ind_tot, J, h, dt, meas_basis, True)\n",
        "        )\n",
        "circs = all_circs_mirror"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "a4b0476d",
      "metadata": {},
      "source": [
        "<span id=\"step-3-execute-using-qiskit-primitives\" />\n",
        "\n",
        "## Paso 3: Ejecutar utilizando Qiskit primitives\n",
        "\n",
        "<span id=\"run-mps-simulation\" />\n",
        "\n",
        "### Ejecutar simulación MPS\n",
        "\n",
        "La lista de circuitos trotterizados se ejecuta utilizando el simulador `matrix_product_state` con una elección arbitraria de $4096$ disparos. El método MPS proporciona una aproximación eficiente de la dinámica del circuito, con una precisión determinada por la dimensión de enlace elegida. Para los tamaños de sistema considerados aquí, la dimensión de enlace por defecto es suficiente para capturar la dinámica de magnetización con alta fidelidad. Los recuentos brutos se normalizan, y a partir de ellos calculamos los valores de expectativa de un solo qubit $\\langle Z_i \\rangle$ en cada paso de Trotter. Por último, calculamos la media de todos los qubits para obtener una curva única que muestre cómo cambia la magnetización con el tiempo.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 12,
      "id": "3709531f",
      "metadata": {},
      "outputs": [],
      "source": [
        "backend_sim = AerSimulator(method=\"matrix_product_state\")\n",
        "\n",
        "\n",
        "def normalize_counts(counts_list, shots):\n",
        "    new_counts_list = []\n",
        "    for counts in counts_list:\n",
        "        a = {k: v / shots for k, v in counts.items()}\n",
        "        new_counts_list.append(a)\n",
        "    return new_counts_list\n",
        "\n",
        "\n",
        "def run_sim(circ_list):\n",
        "    shots = 4096\n",
        "    res = backend_sim.run(circ_list, shots=shots)\n",
        "    normed = normalize_counts(res.result().get_counts(), shots)\n",
        "    return normed\n",
        "\n",
        "\n",
        "sim_counts = run_sim(circs)"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "5895aa46",
      "metadata": {},
      "source": [
        "<span id=\"run-on-hardware\" />\n",
        "\n",
        "### Ejecutar en hardware\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 14,
      "id": "4b5a2f87",
      "metadata": {},
      "outputs": [],
      "source": [
        "service = QiskitRuntimeService()\n",
        "backend = service.backend(\"ibm_marrakesh\")\n",
        "\n",
        "\n",
        "def run_qiskit(circ_list):\n",
        "    shots = 4096\n",
        "    pm = generate_preset_pass_manager(backend=backend)\n",
        "    isa_circuits = [pm.run(qc) for qc in circ_list]\n",
        "    sampler = Sampler(mode=backend)\n",
        "    res = sampler.run(isa_circuits, shots=shots)\n",
        "    res = [r.data.c.get_counts() for r in res.result()]\n",
        "    normed = normalize_counts(res, shots)\n",
        "    return normed\n",
        "\n",
        "\n",
        "qiskit_counts = run_qiskit(circs)"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "d30269ee",
      "metadata": {},
      "source": [
        "<span id=\"run-on-hardware-with-fire-opal\" />\n",
        "\n",
        "### Ejecutar en hardware con Fire Opal\n",
        "\n",
        "Evaluamos la dinámica de magnetización en hardware cuántico real. Fire Opal proporciona una función Qiskit que amplía la primitiva del estimador estándar Qiskit Runtime con supresión automática de errores y gestión del rendimiento. Enviamos los circuitos Trotterizados directamente a un backend IBM® mientras Fire Opal se encarga de la ejecución consciente del ruido.\n",
        "\n",
        "Preparamos una lista de `pubs`, donde cada elemento contiene un circuito y los observables Pauli-Z correspondientes. Estos se pasan a la función estimadora de Fire Opal, que devuelve los valores de expectativa $\\langle Z_i \\rangle$ para cada qubit en cada paso de Trotter. A continuación, los resultados pueden promediarse sobre los qubits para obtener la curva de magnetización a partir del hardware.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "id": "ca8348c9",
      "metadata": {},
      "outputs": [],
      "source": [
        "backend_name = \"ibm_marrakesh\"\n",
        "estimator_pubs = [(qc, observables) for qc in all_circs_mirror[:]]\n",
        "\n",
        "# Run the circuit using the estimator\n",
        "qctrl_estimator_job = perf_mgmt.run(\n",
        "    primitive=\"estimator\",\n",
        "    pubs=estimator_pubs,\n",
        "    backend_name=backend_name,\n",
        "    options={\"default_shots\": 4096},\n",
        ")\n",
        "\n",
        "result_qctrl = qctrl_estimator_job.result()"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "aa081308",
      "metadata": {},
      "source": [
        "<span id=\"step-4-post-process-and-return-result-in-desired-classical-format\" />\n",
        "\n",
        "## Paso 4: Procesamiento posterior y devolución del resultado en el formato clásico deseado\n",
        "\n",
        "Por último, comparamos la curva de magnetización del simulador con los resultados obtenidos en hardware real. Si se comparan ambos gráficos, se aprecia hasta qué punto la ejecución del hardware con Fire Opal coincide con la línea de base sin ruido en los pasos de Trotter.\n",
        "\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 102,
      "id": "91dd23a5",
      "metadata": {},
      "outputs": [],
      "source": [
        "def make_correlators(test_counts, nq, d_ind_tot):\n",
        "    mz = np.empty((nq, d_ind_tot))\n",
        "    for d_ind in range(d_ind_tot):\n",
        "        counts = test_counts[d_ind]\n",
        "        for i in range(nq):\n",
        "            mz[i, d_ind] = z_expectation(counts, i)\n",
        "    average_z = np.mean(mz, axis=0)\n",
        "    return np.concatenate((np.array([1]), average_z), axis=0)\n",
        "\n",
        "\n",
        "sim_exp = make_correlators(sim_counts[0:22], nq=nq, d_ind_tot=22)\n",
        "qiskit_exp = make_correlators(qiskit_counts[0:22], nq=nq, d_ind_tot=22)"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 103,
      "id": "1581f9f0",
      "metadata": {},
      "outputs": [],
      "source": [
        "qctrl_exp = [ev.data.evs for ev in result_qctrl[:]]\n",
        "qctrl_exp_mean = np.concatenate(\n",
        "    (np.array([1]), np.mean(qctrl_exp, axis=1)), axis=0\n",
        ")"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 26,
      "id": "d1f90811",
      "metadata": {},
      "outputs": [],
      "source": [
        "def make_expectations_plot(\n",
        "    sim_z,\n",
        "    depths,\n",
        "    exp_qctrl=None,\n",
        "    exp_qctrl_error=None,\n",
        "    exp_qiskit=None,\n",
        "    exp_qiskit_error=None,\n",
        "    plot_from=0,\n",
        "    plot_upto=23,\n",
        "):\n",
        "    import numpy as np\n",
        "    import matplotlib.pyplot as plt\n",
        "\n",
        "    depth_ticks = [0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22]\n",
        "\n",
        "    d = np.asarray(depths)[plot_from:plot_upto]\n",
        "    sim = np.asarray(sim_z)[plot_from:plot_upto]\n",
        "\n",
        "    qk = (\n",
        "        None\n",
        "        if exp_qiskit is None\n",
        "        else np.asarray(exp_qiskit)[plot_from:plot_upto]\n",
        "    )\n",
        "    qc = (\n",
        "        None\n",
        "        if exp_qctrl is None\n",
        "        else np.asarray(exp_qctrl)[plot_from:plot_upto]\n",
        "    )\n",
        "\n",
        "    qk_err = (\n",
        "        None\n",
        "        if exp_qiskit_error is None\n",
        "        else np.asarray(exp_qiskit_error)[plot_from:plot_upto]\n",
        "    )\n",
        "    qc_err = (\n",
        "        None\n",
        "        if exp_qctrl_error is None\n",
        "        else np.asarray(exp_qctrl_error)[plot_from:plot_upto]\n",
        "    )\n",
        "\n",
        "    # ---- helper(s) ----\n",
        "    def rmse(a, b):\n",
        "        if a is None or b is None:\n",
        "            return None\n",
        "        a = np.asarray(a, dtype=float)\n",
        "        b = np.asarray(b, dtype=float)\n",
        "        mask = np.isfinite(a) & np.isfinite(b)\n",
        "        if not np.any(mask):\n",
        "            return None\n",
        "        diff = a[mask] - b[mask]\n",
        "        return float(np.sqrt(np.mean(diff**2)))\n",
        "\n",
        "    def plot_panel(ax, method_y, method_err, color, label, band_color=None):\n",
        "        # Noiseless reference\n",
        "        ax.plot(d, sim, color=\"grey\", label=\"Noiseless simulation\")\n",
        "\n",
        "        # Method line + band\n",
        "        if method_y is not None:\n",
        "            ax.plot(d, method_y, color=color, label=label)\n",
        "            if method_err is not None:\n",
        "                lo = np.clip(method_y - method_err, -1.05, 1.05)\n",
        "                hi = np.clip(method_y + method_err, -1.05, 1.05)\n",
        "                ax.fill_between(\n",
        "                    d,\n",
        "                    lo,\n",
        "                    hi,\n",
        "                    alpha=0.18,\n",
        "                    color=band_color if band_color else color,\n",
        "                    label=f\"{label} ± error\",\n",
        "                )\n",
        "        else:\n",
        "            ax.text(\n",
        "                0.5,\n",
        "                0.5,\n",
        "                \"No data\",\n",
        "                transform=ax.transAxes,\n",
        "                ha=\"center\",\n",
        "                va=\"center\",\n",
        "                fontsize=10,\n",
        "                color=\"0.4\",\n",
        "            )\n",
        "\n",
        "        # RMSE box (vs sim)\n",
        "        r = rmse(method_y, sim)\n",
        "        if r is not None:\n",
        "            ax.text(\n",
        "                0.98,\n",
        "                0.02,\n",
        "                f\"RMSE: {r:.4f}\",\n",
        "                transform=ax.transAxes,\n",
        "                va=\"bottom\",\n",
        "                ha=\"right\",\n",
        "                fontsize=8,\n",
        "                bbox=dict(\n",
        "                    boxstyle=\"round,pad=0.35\", fc=\"white\", ec=\"0.7\", alpha=0.9\n",
        "                ),\n",
        "            )\n",
        "        # Axes\n",
        "        ax.set_xticks(depth_ticks)\n",
        "        ax.set_ylim(-1.05, 1.05)\n",
        "        ax.grid(True, which=\"both\", linewidth=0.4, alpha=0.4)\n",
        "        ax.set_axisbelow(True)\n",
        "        ax.legend(prop={\"size\": 8}, loc=\"best\")\n",
        "\n",
        "    fig, axes = plt.subplots(1, 2, figsize=(10, 4), dpi=300, sharey=True)\n",
        "\n",
        "    axes[0].set_title(\"Fire Opal (Q-CTRL)\", fontsize=10)\n",
        "    plot_panel(\n",
        "        axes[0],\n",
        "        qc,\n",
        "        qc_err,\n",
        "        color=\"#680CE9\",\n",
        "        label=\"Fire Opal\",\n",
        "        band_color=\"#680CE9\",\n",
        "    )\n",
        "    axes[0].set_xlabel(\"Trotter step\")\n",
        "    axes[0].set_ylabel(r\"$\\langle Z \\rangle$\")\n",
        "    axes[1].set_title(\"Qiskit\", fontsize=10)\n",
        "    plot_panel(\n",
        "        axes[1], qk, qk_err, color=\"blue\", label=\"Qiskit\", band_color=\"blue\"\n",
        "    )\n",
        "    axes[1].set_xlabel(\"Trotter step\")\n",
        "\n",
        "    plt.tight_layout()\n",
        "    plt.show()"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 27,
      "id": "415760ad",
      "metadata": {},
      "outputs": [],
      "source": [
        "depths = list(range(d_ind_tot + 1))\n",
        "errors = np.abs(np.array(qctrl_exp_mean) - np.array(sim_exp))\n",
        "\n",
        "errors_qiskit = np.abs(np.array(qiskit_exp) - np.array(sim_exp))"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": 28,
      "id": "d4902d14",
      "metadata": {},
      "outputs": [
        {
          "data": {
            "text/plain": [
              "<Image src=\"/docs/images/tutorials/transverse-field-ising-model/extracted-outputs/d4902d14-0.avif\" alt=\"Output of the previous code cell\" />"
            ]
          },
          "metadata": {},
          "output_type": "display_data"
        }
      ],
      "source": [
        "make_expectations_plot(\n",
        "    sim_exp,\n",
        "    depths,\n",
        "    exp_qctrl=qctrl_exp_mean,\n",
        "    exp_qctrl_error=errors,\n",
        "    exp_qiskit=qiskit_exp,\n",
        "    exp_qiskit_error=errors_qiskit,\n",
        ")"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "ee41a301",
      "metadata": {},
      "source": [
        "<span id=\"references\" />\n",
        "\n",
        "## Referencias\n",
        "\n",
        "\\[1] Coloreado de gráficos. Wikipedia. Extraído el 15 de septiembre de 2025, de [https://en.wikipedia.org/wiki/Graph \\_coloring](https://en.wikipedia.org/wiki/Graph_coloring)\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "id": "2cb5785c",
      "metadata": {},
      "source": [
        "<span id=\"tutorial-survey\" />\n",
        "\n",
        "## Encuesta tutorial\n",
        "\n",
        "Tómese un minuto para comentar este tutorial. Su opinión nos ayudará a mejorar nuestra oferta de contenidos y la experiencia de los usuarios.\n",
        "\n",
        "[Enlace a la encuesta](https://your.feedback.ibm.com/jfe/form/SV_3BLFkNVEuh0QBWm)\n",
        "\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "id": "a1b8767d",
      "source": "© IBM Corp., 2017-2026"
    }
  ],
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      "nbconvert_exporter": "python",
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    "hours": 1,
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