{
  "schema": "wai.quantum.exercise/1",
  "id": "noise",
  "translations": { "zh-CN": "machine-assisted: to be reviewed by a fluent reader before it is advertised" },
  "title": { "en": "Every gate is a chance to go wrong", "zh-CN": "每个门都是一次出错的机会" },
  "task": {
    "en": "This program reaches 11, but it runs on a noisy device: each one-qubit gate depolarizes with probability 0.01, each two-qubit gate with 0.03. Rewrite it so that it still reaches 11 and, under that noise, its distribution is within 0.02 of always 11.",
    "zh-CN": "这个程序能到达 11，但它运行在一台有噪声的设备上：每个单比特门以 0.01 的概率发生去极化，每个双比特门以 0.03 的概率发生去极化。重写它，使它仍然到达 11，并且在这种噪声下，它的分布与“总是 11”的距离不超过 0.02。"
  },
  "starter": [
    "OPENQASM 3.0;",
    "include \"stdgates.inc\";",
    "qubit[2] q;",
    "bit[2] c;",
    "x q[0];",
    "x q[0];",
    "x q[0];",
    "h q[1];",
    "h q[1];",
    "x q[1];",
    "cx q[0], q[1];",
    "cx q[0], q[1];",
    "c = measure q;"
  ],
  "job": { "noise": { "depolarizing_1q": 0.01, "depolarizing_2q": 0.03 } },
  "intent": { "distribution": { "11": 1.0 }, "tolerance": 0.02 },
  "hints": {
    "en": [
      "The program's result does not need most of its gates. Which pairs of gates do nothing together?",
      "A two-qubit gate costs three times the noise of a one-qubit gate here. The cheapest program that reaches 11 uses no two-qubit gate at all."
    ],
    "zh-CN": [
      "这个程序的结果用不着它的大部分门。哪些成对的门合起来什么也不做？",
      "在这里，一个双比特门的噪声是单比特门的三倍。到达 11 的最便宜的程序根本不用双比特门。"
    ]
  },
  "reference": [
    "OPENQASM 3.0;",
    "include \"stdgates.inc\";",
    "qubit[2] q;",
    "bit[2] c;",
    "x q[0];",
    "x q[1];",
    "c = measure q;"
  ],
  "wrong": [
    {
      "fails": "intent",
      "note": "a two-qubit gate's noise alone exceeds the tolerance",
      "qasm": ["OPENQASM 3.0;", "include \"stdgates.inc\";", "qubit[2] q;", "bit[2] c;", "x q[0];", "cx q[0], q[1];", "c = measure q;"]
    }
  ]
}