{
  "schema": "wai.quantum.exercise/1",
  "id": "ghz",
  "translations": { "zh-CN": "machine-assisted: to be reviewed by a fluent reader before it is advertised" },
  "title": { "en": "Three in agreement, with the right sign", "zh-CN": "三个比特一致，而且符号正确" },
  "task": {
    "en": "Three qubits. Prepare the state (|000⟩ + |111⟩)/√2, with a plus sign, and measure every qubit into c. The check compares the state itself, not only its outcomes.",
    "zh-CN": "三个量子比特。制备状态 (|000⟩ + |111⟩)/√2（加号），并把每个量子比特都测量到 c 中。检查比较的是状态本身，而不只是结果。"
  },
  "starter": [
    "OPENQASM 3.0;",
    "include \"stdgates.inc\";",
    "qubit[3] q;",
    "bit[3] c;",
    "// your gates here",
    "c = measure q;"
  ],
  "intent": {
    "prepares": "OPENQASM 3.0;\ninclude \"stdgates.inc\";\nqubit[3] q;\nbit[3] c;\nh q[0];\ncx q[0], q[1];\ncx q[0], q[2];\nc = measure q;\n"
  },
  "hints": {
    "en": [
      "Start from the Bell pair and bring a third qubit into the agreement.",
      "The state (|000⟩ − |111⟩)/√2 has the same outcomes and is a different state: watch for a stray z."
    ],
    "zh-CN": [
      "从 Bell 对出发，再让第三个量子比特也加入这种一致。",
      "状态 (|000⟩ − |111⟩)/√2 的结果相同，却是另一个状态：留意多余的 z。"
    ]
  },
  "reference": [
    "OPENQASM 3.0;",
    "include \"stdgates.inc\";",
    "qubit[3] q;",
    "bit[3] c;",
    "h q[0];",
    "cx q[0], q[1];",
    "cx q[1], q[2];",
    "c = measure q;"
  ],
  "wrong": [
    {
      "fails": "intent",
      "note": "the same outcomes with a minus sign: a different state",
      "qasm": ["OPENQASM 3.0;", "include \"stdgates.inc\";", "qubit[3] q;", "bit[3] c;", "h q[0];", "cx q[0], q[1];", "cx q[1], q[2];", "z q[0];", "c = measure q;"]
    },
    {
      "fails": "intent",
      "note": "only two qubits agree",
      "qasm": ["OPENQASM 3.0;", "include \"stdgates.inc\";", "qubit[3] q;", "bit[3] c;", "h q[0];", "cx q[0], q[1];", "c = measure q;"]
    }
  ]
}