{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Quantum Die"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "import math\n",
    "from pyquil import Program, get_qc\n",
    "from pyquil.gates import H"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [],
   "source": [
    "def qubits_needed(number_of_sides):\n",
    "    \"\"\"\n",
    "    The number of qubits needed for a die of n faces.\n",
    "    \"\"\"\n",
    "    return int(math.ceil(math.log(number_of_sides, 2)))\n",
    "\n",
    "\n",
    "def get_qvm(number_of_sides):\n",
    "    \"\"\"\n",
    "    Get a QVM to simulate the requested number of sides.\n",
    "    \"\"\"\n",
    "    return get_qc(f\"{qubits_needed(number_of_sides)}q-qvm\")\n",
    "\n",
    "\n",
    "def die_program(number_of_sides):\n",
    "    \"\"\"\n",
    "    Generate a quantum program to roll a die of n faces.\n",
    "    \"\"\"\n",
    "    prog = Program()\n",
    "    n_qubits = qubits_needed(number_of_sides)\n",
    "    ro = prog.declare(\"ro\", \"BIT\", n_qubits)\n",
    "    # Hadamard initialize.\n",
    "    for q in range(n_qubits):\n",
    "        prog.inst(H(q))\n",
    "    # Measure everything.\n",
    "    for q in range(n_qubits):\n",
    "        prog.measure(q, ro[q])\n",
    "    return prog\n",
    "\n",
    "\n",
    "def process_results(results):\n",
    "    \"\"\"\n",
    "    Convert n digit binary result from the QVM to a value on a die.\n",
    "    \"\"\"\n",
    "    raw_results = results[0]\n",
    "    processing_result = 0\n",
    "    for each_qubit_measurement in raw_results:\n",
    "        processing_result = 2 * processing_result + each_qubit_measurement\n",
    "    # Convert from 0 indexed to 1 indexed\n",
    "    die_value = processing_result + 1\n",
    "    return die_value\n",
    "\n",
    "\n",
    "def roll_die(qvm, number_of_sides):\n",
    "    \"\"\"\n",
    "    Roll an n-sided quantum die.\n",
    "    \"\"\"\n",
    "    die_compiled = qvm.compile(die_program(number_of_sides))\n",
    "    return process_results(qvm.run(die_compiled))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "The result is: 2\n"
     ]
    }
   ],
   "source": [
    "number_of_sides = 5\n",
    "\n",
    "qvm = get_qvm(number_of_sides)\n",
    "die_value = roll_die(qvm, number_of_sides)\n",
    "while die_value > number_of_sides:\n",
    "    die_value = roll_die(qvm, number_of_sides)\n",
    "print(f\"The result is: {die_value}\")"
   ]
  }
 ],
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