PhaseOracle
class qiskit.circuit.library.PhaseOracle(expression, synthesizer=None, var_order=None)
Bases: 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, which is the standard format for specifying SATisfiability (SAT) problem instances in Conjunctive Normal Form (CNF), 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, ClassicalElement]) – A Python-like boolean expression.
- synthesizer (Optional[Callable[[BooleanExpression], 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) – 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}}
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. 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
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
.
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: 287
layout
Return any associated layout information about the circuit
This attribute contains an optional TranspileLayout
object. This is typically set on the output from transpile()
or 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()
function, an initial layout which permutes the qubits based on the selected physical qubits on the Target
, and a final layout which is an output permutation caused by 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
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
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 – When circuit is not scheduled.
parameters
The parameters defined in the circuit.
This attribute returns the Parameter
objects in the circuit sorted alphabetically. Note that parameters instantiated with a ParameterVector
are still sorted numerically.
Examples
The snippet below shows that insertion order of parameters does not matter.
>>> 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.
>>> 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
can be used.
>>> 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
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
is specified in.
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)
Evaluate the oracle on a bitstring. This evaluation is done classically without any quantum circuit.
Parameters
bitstring (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
from_dimacs_file
classmethod from_dimacs_file(filename)
Create a PhaseOracle from the string in the DIMACS format.
It is possible to build a PhaseOracle from a file in DIMACS CNF format, which is the standard format for specifying SATisfiability (SAT) problem instances in Conjunctive Normal Form (CNF), 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:
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 , and contains five clauses. The five clauses, listed afterwards, are implicitly joined by the logical AND operator, , while the variables in each clause, represented by their indices, are implicitly disjoined by the logical OR operator, . The symbol preceding a boolean variable index corresponds to the logical NOT operator, . Character 0 (zero) marks the end of each clause. Essentially, the code above corresponds to the following CNF:
.
Parameters
filename (str) – A file in DIMACS format.
Returns
A quantum circuit with a phase oracle.
Return type