321 lines
14 KiB
Plaintext
321 lines
14 KiB
Plaintext
---
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title: PhaseOracle (v1.2)
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description: API reference for qiskit.circuit.library.PhaseOracle in qiskit v1.2
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in_page_toc_min_heading_level: 1
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python_api_type: class
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python_api_name: qiskit.circuit.library.PhaseOracle
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---
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# PhaseOracle
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<Class id="qiskit.circuit.library.PhaseOracle" isDedicatedPage={true} github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/phase_oracle.py#L28-L153" signature="qiskit.circuit.library.PhaseOracle(expression, synthesizer=None, var_order=None)" modifiers="class">
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Bases: [`QuantumCircuit`](qiskit.circuit.QuantumCircuit "qiskit.circuit.quantumcircuit.QuantumCircuit")
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Phase Oracle.
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The Phase Oracle object constructs circuits for any arbitrary input logical expressions. A logical expression is composed of logical operators & (AND), | (OR), \~ (NOT), and ^ (XOR). as well as symbols for literals (variables). For example, ‘a & b’, and (v0 | \~v1) & (\~v2 & v3) are both valid string representation of boolean logical expressions.
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For convenience, this oracle, in addition to parsing arbitrary logical expressions, also supports input strings in the [DIMACS CNF format](http://www.satcompetition.org/2009/format-benchmarks2009.html), which is the standard format for specifying SATisfiability (SAT) problem instances in [Conjunctive Normal Form (CNF)](https://en.wikipedia.org/wiki/Conjunctive_normal_form), which is a conjunction of one or more clauses, where a clause is a disjunction of one or more literals. See `qiskit.circuit.library.phase_oracle.PhaseOracle.from_dimacs_file()`.
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From 16 variables on, possible performance issues should be expected when using the default synthesizer.
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Creates a PhaseOracle object
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**Parameters**
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* **expression** (*Union\[*[*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")*, ClassicalElement]*) – A Python-like boolean expression.
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* **synthesizer** (*Optional\[Callable\[\[*[*BooleanExpression*](qiskit.circuit.classicalfunction.BooleanExpression "qiskit.circuit.classicalfunction.BooleanExpression")*],* [*QuantumCircuit*](qiskit.circuit.QuantumCircuit "qiskit.circuit.QuantumCircuit")*]]*) – Optional. A function to convert a BooleanExpression into a QuantumCircuit If None is provided, Tweedledum’s pkrm\_synth with phase\_esop will be used.
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* **var\_order** ([*list*](https://docs.python.org/3/library/stdtypes.html#list "(in Python v3.13)")) – A list with the order in which variables will be created. (default: by appearance)
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## Attributes
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### ancillas
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<Attribute id="qiskit.circuit.library.PhaseOracle.ancillas">
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A list of `AncillaQubit`s in the order that they were added. You should not mutate this.
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</Attribute>
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### calibrations
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<Attribute id="qiskit.circuit.library.PhaseOracle.calibrations">
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Return calibration dictionary.
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The custom pulse definition of a given gate is of the form `{'gate_name': {(qubits, params): schedule}}`
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</Attribute>
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### clbits
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<Attribute id="qiskit.circuit.library.PhaseOracle.clbits">
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A list of `Clbit`s in the order that they were added. You should not mutate this.
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</Attribute>
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### data
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<Attribute id="qiskit.circuit.library.PhaseOracle.data">
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The circuit data (instructions and context).
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**Returns**
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a list-like object containing the [`CircuitInstruction`](qiskit.circuit.CircuitInstruction "qiskit.circuit.CircuitInstruction")s for each instruction.
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**Return type**
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QuantumCircuitData
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</Attribute>
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### global\_phase
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<Attribute id="qiskit.circuit.library.PhaseOracle.global_phase">
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The global phase of the current circuit scope in radians.
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</Attribute>
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### instances
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<Attribute id="qiskit.circuit.library.PhaseOracle.instances" attributeValue="254" />
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### layout
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<Attribute id="qiskit.circuit.library.PhaseOracle.layout">
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Return any associated layout information about the circuit
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This attribute contains an optional [`TranspileLayout`](qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout") object. This is typically set on the output from [`transpile()`](compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") or [`PassManager.run()`](qiskit.transpiler.PassManager#run "qiskit.transpiler.PassManager.run") to retain information about the permutations caused on the input circuit by transpilation.
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There are two types of permutations caused by the [`transpile()`](compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") function, an initial layout which permutes the qubits based on the selected physical qubits on the [`Target`](qiskit.transpiler.Target "qiskit.transpiler.Target"), and a final layout which is an output permutation caused by [`SwapGate`](qiskit.circuit.library.SwapGate "qiskit.circuit.library.SwapGate")s inserted during routing.
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</Attribute>
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### metadata
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<Attribute id="qiskit.circuit.library.PhaseOracle.metadata">
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Arbitrary user-defined metadata for the circuit.
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Qiskit will not examine the content of this mapping, but it will pass it through the transpiler and reattach it to the output, so you can track your own metadata.
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</Attribute>
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### num\_ancillas
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_ancillas">
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Return the number of ancilla qubits.
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</Attribute>
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### num\_captured\_vars
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_captured_vars">
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The number of real-time classical variables in the circuit marked as captured from an enclosing scope.
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This is the length of the `iter_captured_vars()` iterable. If this is non-zero, [`num_input_vars`](#qiskit.circuit.library.PhaseOracle.num_input_vars "qiskit.circuit.library.PhaseOracle.num_input_vars") must be zero.
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</Attribute>
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### num\_clbits
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_clbits">
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Return number of classical bits.
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</Attribute>
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### num\_declared\_vars
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_declared_vars">
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The number of real-time classical variables in the circuit that are declared by this circuit scope, excluding inputs or captures.
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This is the length of the `iter_declared_vars()` iterable.
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</Attribute>
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### num\_input\_vars
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_input_vars">
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The number of real-time classical variables in the circuit marked as circuit inputs.
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This is the length of the `iter_input_vars()` iterable. If this is non-zero, [`num_captured_vars`](#qiskit.circuit.library.PhaseOracle.num_captured_vars "qiskit.circuit.library.PhaseOracle.num_captured_vars") must be zero.
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</Attribute>
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### num\_parameters
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_parameters">
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The number of parameter objects in the circuit.
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</Attribute>
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### num\_qubits
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_qubits">
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Return number of qubits.
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</Attribute>
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### num\_vars
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<Attribute id="qiskit.circuit.library.PhaseOracle.num_vars">
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The number of real-time classical variables in the circuit.
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This is the length of the `iter_vars()` iterable.
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</Attribute>
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### op\_start\_times
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<Attribute id="qiskit.circuit.library.PhaseOracle.op_start_times">
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Return a list of operation start times.
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This attribute is enabled once one of scheduling analysis passes runs on the quantum circuit.
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**Returns**
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List of integers representing instruction start times. The index corresponds to the index of instruction in `QuantumCircuit.data`.
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**Raises**
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[**AttributeError**](https://docs.python.org/3/library/exceptions.html#AttributeError "(in Python v3.13)") – When circuit is not scheduled.
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</Attribute>
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### parameters
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<Attribute id="qiskit.circuit.library.PhaseOracle.parameters">
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The parameters defined in the circuit.
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This attribute returns the [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects in the circuit sorted alphabetically. Note that parameters instantiated with a [`ParameterVector`](qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector") are still sorted numerically.
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**Examples**
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The snippet below shows that insertion order of parameters does not matter.
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```python
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>>> from qiskit.circuit import QuantumCircuit, Parameter
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>>> a, b, elephant = Parameter("a"), Parameter("b"), Parameter("elephant")
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>>> circuit = QuantumCircuit(1)
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>>> circuit.rx(b, 0)
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>>> circuit.rz(elephant, 0)
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>>> circuit.ry(a, 0)
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>>> circuit.parameters # sorted alphabetically!
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ParameterView([Parameter(a), Parameter(b), Parameter(elephant)])
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```
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Bear in mind that alphabetical sorting might be unintuitive when it comes to numbers. The literal “10” comes before “2” in strict alphabetical sorting.
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```python
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>>> from qiskit.circuit import QuantumCircuit, Parameter
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>>> angles = [Parameter("angle_1"), Parameter("angle_2"), Parameter("angle_10")]
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>>> circuit = QuantumCircuit(1)
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>>> circuit.u(*angles, 0)
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>>> circuit.draw()
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┌─────────────────────────────┐
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q: ┤ U(angle_1,angle_2,angle_10) ├
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└─────────────────────────────┘
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>>> circuit.parameters
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ParameterView([Parameter(angle_1), Parameter(angle_10), Parameter(angle_2)])
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```
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To respect numerical sorting, a [`ParameterVector`](qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector") can be used.
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```python
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>>> from qiskit.circuit import QuantumCircuit, Parameter, ParameterVector
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>>> x = ParameterVector("x", 12)
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>>> circuit = QuantumCircuit(1)
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>>> for x_i in x:
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... circuit.rx(x_i, 0)
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>>> circuit.parameters
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ParameterView([
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ParameterVectorElement(x[0]), ParameterVectorElement(x[1]),
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ParameterVectorElement(x[2]), ParameterVectorElement(x[3]),
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..., ParameterVectorElement(x[11])
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])
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```
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**Returns**
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The sorted [`Parameter`](qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects in the circuit.
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</Attribute>
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### prefix
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<Attribute id="qiskit.circuit.library.PhaseOracle.prefix" attributeValue="'circuit'" />
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### qubits
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<Attribute id="qiskit.circuit.library.PhaseOracle.qubits">
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A list of `Qubit`s in the order that they were added. You should not mutate this.
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</Attribute>
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### name
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<Attribute id="qiskit.circuit.library.PhaseOracle.name" attributeTypeHint="str">
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A human-readable name for the circuit.
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</Attribute>
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### qregs
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<Attribute id="qiskit.circuit.library.PhaseOracle.qregs" attributeTypeHint="list[QuantumRegister]">
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A list of the `QuantumRegister`s in this circuit. You should not mutate this.
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</Attribute>
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### cregs
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<Attribute id="qiskit.circuit.library.PhaseOracle.cregs" attributeTypeHint="list[ClassicalRegister]">
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A list of the `ClassicalRegister`s in this circuit. You should not mutate this.
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</Attribute>
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### duration
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<Attribute id="qiskit.circuit.library.PhaseOracle.duration" attributeTypeHint="int | float | None">
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The total duration of the circuit, set by a scheduling transpiler pass. Its unit is specified by [`unit`](#qiskit.circuit.library.PhaseOracle.unit "qiskit.circuit.library.PhaseOracle.unit").
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</Attribute>
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### unit
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<Attribute id="qiskit.circuit.library.PhaseOracle.unit">
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The unit that [`duration`](#qiskit.circuit.library.PhaseOracle.duration "qiskit.circuit.library.PhaseOracle.duration") is specified in.
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</Attribute>
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## Methods
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### evaluate\_bitstring
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<Function id="qiskit.circuit.library.PhaseOracle.evaluate_bitstring" github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/phase_oracle.py#L92-L103" signature="evaluate_bitstring(bitstring)">
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Evaluate the oracle on a bitstring. This evaluation is done classically without any quantum circuit.
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**Parameters**
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**bitstring** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) – The bitstring for which to evaluate. The input bitstring is expected to be in little-endian order.
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**Returns**
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True if the bitstring is a good state, False otherwise.
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**Return type**
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[bool](https://docs.python.org/3/library/functions.html#bool "(in Python v3.13)")
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</Function>
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### from\_dimacs\_file
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<Function id="qiskit.circuit.library.PhaseOracle.from_dimacs_file" github="https://github.com/Qiskit/qiskit/tree/stable/1.2/qiskit/circuit/library/phase_oracle.py#L105-L153" signature="from_dimacs_file(filename)" modifiers="classmethod">
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Create a PhaseOracle from the string in the DIMACS format.
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It is possible to build a PhaseOracle from a file in [DIMACS CNF format](http://www.satcompetition.org/2009/format-benchmarks2009.html), which is the standard format for specifying SATisfiability (SAT) problem instances in [Conjunctive Normal Form (CNF)](https://en.wikipedia.org/wiki/Conjunctive_normal_form), which is a conjunction of one or more clauses, where a clause is a disjunction of one or more literals.
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The following is an example of a CNF expressed in the DIMACS format:
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```text
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c DIMACS CNF file with 3 satisfying assignments: 1 -2 3, -1 -2 -3, 1 2 -3.
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p cnf 3 5
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-1 -2 -3 0
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1 -2 3 0
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1 2 -3 0
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1 -2 -3 0
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-1 2 3 0
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```
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The first line, following the c character, is a comment. The second line specifies that the CNF is over three boolean variables — let us call them $x_1, x_2, x_3$, and contains five clauses. The five clauses, listed afterwards, are implicitly joined by the logical AND operator, $\land$, while the variables in each clause, represented by their indices, are implicitly disjoined by the logical OR operator, $lor$. The $-$ symbol preceding a boolean variable index corresponds to the logical NOT operator, $lnot$. Character 0 (zero) marks the end of each clause. Essentially, the code above corresponds to the following CNF:
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$(\lnot x_1 \lor \lnot x_2 \lor \lnot x_3) \land (x_1 \lor \lnot x_2 \lor x_3) \land (x_1 \lor x_2 \lor \lnot x_3) \land (x_1 \lor \lnot x_2 \lor \lnot x_3) \land (\lnot x_1 \lor x_2 \lor x_3)$.
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**Parameters**
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**filename** ([*str*](https://docs.python.org/3/library/stdtypes.html#str "(in Python v3.13)")) – A file in DIMACS format.
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**Returns**
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A quantum circuit with a phase oracle.
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**Return type**
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[PhaseOracle](#qiskit.circuit.library.PhaseOracle "qiskit.circuit.library.PhaseOracle")
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</Function>
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</Class>
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