| Qiskit 1.0 migration notes |
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| Scope: circuit construction, transpilation, and backend interfaces only. |
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| ## Removal notices |
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| ### Execution and backend access |
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| - `qiskit.execute` was removed. Use `transpile(circuit, backend)` followed by `backend.run(...)`. |
| - `qiskit.Aer` was removed from the top-level namespace. Use `qiskit_aer.Aer`. |
| - `qiskit.BasicAer` was removed from the top-level namespace. Use `qiskit.providers.basic_provider`. |
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| ### Circuit construction and serialization |
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| - `QuantumCircuit.qasm` was removed. Use `qiskit.qasm2.dump` or `qiskit.qasm2.dumps`. |
| - `qiskit.converters.ast_to_dag` was removed along with the legacy OpenQASM 2 parser path. Parse into a `QuantumCircuit` with `qiskit.qasm2.load`, `QuantumCircuit.from_qasm_file`, or `QuantumCircuit.from_qasm_str`, then convert with `circuit_to_dag`. |
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| ## API change tables |
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| ### Circuit construction: gate helpers removed |
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| | Removed | Alternative | |
| | --- | --- | |
| | `QuantumCircuit.cnot` | `QuantumCircuit.cx` | |
| | `QuantumCircuit.toffoli` | `QuantumCircuit.ccx` | |
| | `QuantumCircuit.fredkin` | `QuantumCircuit.cswap` | |
| | `QuantumCircuit.mct` | `QuantumCircuit.mcx` | |
| | `QuantumCircuit.i` | `QuantumCircuit.id` | |
| | `QuantumCircuit.squ` | `QuantumCircuit.unitary` | |
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| ### Circuit construction: methods replaced by `append(...)` |
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| | Removed | Alternative | |
| | --- | --- | |
| | `QuantumCircuit.diagonal` | `QuantumCircuit.append(DiagonalGate(...), qubits)` | |
| | `QuantumCircuit.hamiltonian` | `QuantumCircuit.append(HamiltonianGate(...), qubits)` | |
| | `QuantumCircuit.isometry` | `QuantumCircuit.append(Isometry(...), qubits)` | |
| | `QuantumCircuit.iso` | `QuantumCircuit.append(Isometry(...), qubits)` | |
| | `QuantumCircuit.uc` | `QuantumCircuit.append(UCGate(...), qubits)` | |
| | `QuantumCircuit.ucrx` | `QuantumCircuit.append(UCRXGate(...), qubits)` | |
| | `QuantumCircuit.ucry` | `QuantumCircuit.append(UCRYGate(...), qubits)` | |
| | `QuantumCircuit.ucrz` | `QuantumCircuit.append(UCRZGate(...), qubits)` | |
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| ### Circuit construction: other removed methods |
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| | Removed | Alternative | |
| | --- | --- | |
| | `QuantumCircuit.bind_parameters` | `QuantumCircuit.assign_parameters` | |
| | `QuantumCircuit.snapshot` | `qiskit-aer` save instructions | |
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| ### Transpilation and backend execution |
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| | Removed / changed API | Alternative | |
| | --- | --- | |
| | `qiskit.execute(circuit, backend)` | `backend.run(transpile(circuit, backend))` | |
| | `from qiskit import Aer` | `from qiskit_aer import Aer` | |
| | `from qiskit import BasicAer` | `from qiskit.providers.basic_provider import BasicProvider` | |
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| ### OpenQASM parsing and DAG conversion |
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| | Removed | Alternative | |
| | --- | --- | |
| | `qiskit.converters.ast_to_dag` | `circuit_to_dag(qiskit.qasm2.load(...))` | |
| | `qiskit.qasm.Qasm(...).parse()` workflow | `qiskit.qasm2.load(...)` or `QuantumCircuit.from_qasm_file(...)` | |
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