--- title: PhaseOracle (v1.3) description: API reference for qiskit.circuit.library.PhaseOracle in qiskit v1.3 source: https://eu-de.quantum.cloud.ibm.com/docs/en/api/qiskit/1.3/qiskit.circuit.library.PhaseOracle --- # PhaseOracle *class* `qiskit.circuit.library.PhaseOracle(expression, synthesizer=None, var_order=None)` [GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/phase_oracle.py#L28-L153) Bases: [`QuantumCircuit`](/docs/api/qiskit/1.3/qiskit.circuit.QuantumCircuit "qiskit.circuit.quantumcircuit.QuantumCircuit") Phase Oracle. 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. For convenience, this oracle, in addition to parsing arbitrary logical expressions, also supports input strings in the [DIMACS CNF format](https://satisfiability.org/competition/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()`. From 16 variables on, possible performance issues should be expected when using the default synthesizer. Creates a PhaseOracle object **Parameters** - **expression** (*Union\[*[*str*](https://docs.python.org/3/library/stdtypes.html#str)*, ClassicalElement]*) – A Python-like boolean expression. - **synthesizer** (*Optional\[Callable\[\[*[*BooleanExpression*](/docs/api/qiskit/1.3/qiskit.circuit.classicalfunction.BooleanExpression "qiskit.circuit.classicalfunction.BooleanExpression")*],* [*QuantumCircuit*](/docs/api/qiskit/1.3/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. - **var\_order** ([*list*](https://docs.python.org/3/library/stdtypes.html#list)) – A list with the order in which variables will be created. (default: by appearance) ## Attributes ### ancillas A list of `AncillaQubit`s in the order that they were added. You should not mutate this. ### calibrations Return calibration dictionary. The custom pulse definition of a given gate is of the form `{'gate_name': {(qubits, params): schedule}}` > **Deprecated since version 1.3** > > The property `qiskit.circuit.quantumcircuit.QuantumCircuit.calibrations` is deprecated as of Qiskit 1.3. It will be removed in Qiskit 2.0. The entire Qiskit Pulse package is being deprecated and will be moved to the Qiskit Dynamics repository: [https://github.com/qiskit-community/qiskit-dynamics](https://github.com/qiskit-community/qiskit-dynamics). Note that once removed, `qiskit.circuit.quantumcircuit.QuantumCircuit.calibrations` will have no alternative in Qiskit. ### clbits A list of `Clbit`s in the order that they were added. You should not mutate this. ### data The circuit data (instructions and context). **Returns** a list-like object containing the [`CircuitInstruction`](/docs/api/qiskit/1.3/qiskit.circuit.CircuitInstruction "qiskit.circuit.CircuitInstruction")s for each instruction. **Return type** QuantumCircuitData ### duration 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"). > **Deprecated since version 1.3.0** > > The property `qiskit.circuit.quantumcircuit.QuantumCircuit.duration` is deprecated as of qiskit 1.3.0. It will be removed in Qiskit 2.0.0. ### global\_phase The global phase of the current circuit scope in radians. ### instances Default value: `266` ### layout Return any associated layout information about the circuit This attribute contains an optional [`TranspileLayout`](/docs/api/qiskit/1.3/qiskit.transpiler.TranspileLayout "qiskit.transpiler.TranspileLayout") object. This is typically set on the output from [`transpile()`](/docs/api/qiskit/1.3/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") or [`PassManager.run()`](/docs/api/qiskit/1.3/qiskit.transpiler.PassManager#run "qiskit.transpiler.PassManager.run") to retain information about the permutations caused on the input circuit by transpilation. There are two types of permutations caused by the [`transpile()`](/docs/api/qiskit/1.3/compiler#qiskit.compiler.transpile "qiskit.compiler.transpile") function, an initial layout which permutes the qubits based on the selected physical qubits on the [`Target`](/docs/api/qiskit/1.3/qiskit.transpiler.Target "qiskit.transpiler.Target"), and a final layout which is an output permutation caused by [`SwapGate`](/docs/api/qiskit/1.3/qiskit.circuit.library.SwapGate "qiskit.circuit.library.SwapGate")s inserted during routing. ### metadata Arbitrary user-defined metadata for the circuit. 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. ### num\_ancillas Return the number of ancilla qubits. ### num\_captured\_vars The number of real-time classical variables in the circuit marked as captured from an enclosing scope. 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. ### num\_clbits Return number of classical bits. ### num\_declared\_vars The number of real-time classical variables in the circuit that are declared by this circuit scope, excluding inputs or captures. This is the length of the `iter_declared_vars()` iterable. ### num\_input\_vars The number of real-time classical variables in the circuit marked as circuit inputs. 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. ### num\_parameters The number of parameter objects in the circuit. ### num\_qubits Return number of qubits. ### num\_vars The number of real-time classical variables in the circuit. This is the length of the `iter_vars()` iterable. ### op\_start\_times Return a list of operation start times. This attribute is enabled once one of scheduling analysis passes runs on the quantum circuit. **Returns** List of integers representing instruction start times. The index corresponds to the index of instruction in `QuantumCircuit.data`. **Raises** [**AttributeError**](https://docs.python.org/3/library/exceptions.html#AttributeError) – When circuit is not scheduled. ### parameters The parameters defined in the circuit. This attribute returns the [`Parameter`](/docs/api/qiskit/1.3/qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects in the circuit sorted alphabetically. Note that parameters instantiated with a [`ParameterVector`](/docs/api/qiskit/1.3/qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector") are still sorted numerically. **Examples** The snippet below shows that insertion order of parameters does not matter. ```python >>> from qiskit.circuit import QuantumCircuit, Parameter >>> a, b, elephant = Parameter("a"), Parameter("b"), Parameter("elephant") >>> circuit = QuantumCircuit(1) >>> circuit.rx(b, 0) >>> circuit.rz(elephant, 0) >>> circuit.ry(a, 0) >>> circuit.parameters # sorted alphabetically! ParameterView([Parameter(a), Parameter(b), Parameter(elephant)]) ``` Bear in mind that alphabetical sorting might be unintuitive when it comes to numbers. The literal “10” comes before “2” in strict alphabetical sorting. ```python >>> from qiskit.circuit import QuantumCircuit, Parameter >>> angles = [Parameter("angle_1"), Parameter("angle_2"), Parameter("angle_10")] >>> circuit = QuantumCircuit(1) >>> circuit.u(*angles, 0) >>> circuit.draw() ┌─────────────────────────────┐ q: ┤ U(angle_1,angle_2,angle_10) ├ └─────────────────────────────┘ >>> circuit.parameters ParameterView([Parameter(angle_1), Parameter(angle_10), Parameter(angle_2)]) ``` To respect numerical sorting, a [`ParameterVector`](/docs/api/qiskit/1.3/qiskit.circuit.ParameterVector "qiskit.circuit.ParameterVector") can be used. ```python >>> from qiskit.circuit import QuantumCircuit, Parameter, ParameterVector >>> x = ParameterVector("x", 12) >>> circuit = QuantumCircuit(1) >>> for x_i in x: ... circuit.rx(x_i, 0) >>> circuit.parameters ParameterView([ ParameterVectorElement(x[0]), ParameterVectorElement(x[1]), ParameterVectorElement(x[2]), ParameterVectorElement(x[3]), ..., ParameterVectorElement(x[11]) ]) ``` **Returns** The sorted [`Parameter`](/docs/api/qiskit/1.3/qiskit.circuit.Parameter "qiskit.circuit.Parameter") objects in the circuit. ### prefix Default value: `'circuit'` ### qubits A list of `Qubit`s in the order that they were added. You should not mutate this. ### unit The unit that [`duration`](#qiskit.circuit.library.PhaseOracle.duration "qiskit.circuit.library.PhaseOracle.duration") is specified in. > **Deprecated since version 1.3.0** > > The property `qiskit.circuit.quantumcircuit.QuantumCircuit.unit` is deprecated as of qiskit 1.3.0. It will be removed in Qiskit 2.0.0. ### name Type: `str` A human-readable name for the circuit. ### qregs Type: `list[QuantumRegister]` A list of the `QuantumRegister`s in this circuit. You should not mutate this. ### cregs Type: `list[ClassicalRegister]` A list of the `ClassicalRegister`s in this circuit. You should not mutate this. ## Methods ### evaluate\_bitstring `evaluate_bitstring(bitstring)` [GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/phase_oracle.py#L92-L103) Evaluate the oracle on a bitstring. This evaluation is done classically without any quantum circuit. **Parameters** **bitstring** ([*str*](https://docs.python.org/3/library/stdtypes.html#str)) – The bitstring for which to evaluate. The input bitstring is expected to be in little-endian order. **Returns** True if the bitstring is a good state, False otherwise. **Return type** [bool](https://docs.python.org/3/library/functions.html#bool) ### from\_dimacs\_file *classmethod* `from_dimacs_file(filename)` [GitHub](https://github.com/Qiskit/qiskit/tree/stable/1.3/qiskit/circuit/library/phase_oracle.py#L105-L153) Create a PhaseOracle from the string in the DIMACS format. It is possible to build a PhaseOracle from a file in [DIMACS CNF format](https://satisfiability.org/competition/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. The following is an example of a CNF expressed in the DIMACS format: ```text c DIMACS CNF file with 3 satisfying assignments: 1 -2 3, -1 -2 -3, 1 2 -3. p cnf 3 5 -1 -2 -3 0 1 -2 3 0 1 2 -3 0 1 -2 -3 0 -1 2 3 0 ``` 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: $(\lnot x_1 \lor \lnot x_2 \lor \lnot x_3) \land (x_1 \lor \lnot x_2 \lor x_3) \land (x_1 \lor x_2 \lor \lnot x_3) \land (x_1 \lor \lnot x_2 \lor \lnot x_3) \land (\lnot x_1 \lor x_2 \lor x_3)$. **Parameters** **filename** ([*str*](https://docs.python.org/3/library/stdtypes.html#str)) – A file in DIMACS format. **Returns** A quantum circuit with a phase oracle. **Return type** [PhaseOracle](#qiskit.circuit.library.PhaseOracle "qiskit.circuit.library.PhaseOracle")