ExcitationPreserving
class ExcitationPreserving(num_qubits=None, mode='iswap', entanglement='full', reps=3, skip_unentangled_qubits=False, skip_final_rotation_layer=False, parameter_prefix='θ', insert_barriers=False, initial_state=None, name='ExcitationPreserving')
Bases: qiskit.circuit.library.n_local.two_local.TwoLocal
The heuristic excitation-preserving wave function ansatz.
The ExcitationPreserving circuit preserves the ratio of , and states. To this end, this circuit uses two-qubit interactions of the form
for the mode 'fsim' or with for the mode 'iswap'.
Note that other wave functions, such as UCC-ansatzes, are also excitation preserving. However these can become complex quickly, while this heuristically motivated circuit follows a simpler pattern.
This trial wave function consists of layers of rotations with 2-qubit entanglements. The entangling is creating using rotations and optionally a controlled-phase gate for the mode 'fsim'.
See RealAmplitudes for more detail on the possible arguments and options such as skipping unentanglement qubits, which apply here too.
The rotations of the ExcitationPreserving ansatz can be written as
Examples
>>> ansatz = ExcitationPreserving(3, reps=1, insert_barriers=True, entanglement='linear')
>>> print(ansatz) # show the circuit
┌──────────┐ ░ ┌────────────┐┌────────────┐ ░ ┌──────────┐
q_0: ┤ RZ(θ[0]) ├─░─┤0 ├┤0 ├─────────────────────────────░─┤ RZ(θ[5]) ├
├──────────┤ ░ │ RXX(θ[3]) ││ RYY(θ[3]) │┌────────────┐┌────────────┐ ░ ├──────────┤
q_1: ┤ RZ(θ[1]) ├─░─┤1 ├┤1 ├┤0 ├┤0 ├─░─┤ RZ(θ[6]) ├
├──────────┤ ░ └────────────┘└────────────┘│ RXX(θ[4]) ││ RYY(θ[4]) │ ░ ├──────────┤
q_2: ┤ RZ(θ[2]) ├─░─────────────────────────────┤1 ├┤1 ├─░─┤ RZ(θ[7]) ├
└──────────┘ ░ └────────────┘└────────────┘ ░ └──────────┘>>> ansatz = ExcitationPreserving(2, reps=1)
>>> qc = QuantumCircuit(2) # create a circuit and append the RY variational form
>>> qc.cry(0.2, 0, 1) # do some previous operation
>>> qc.compose(ansatz, inplace=True) # add the swaprz
>>> qc.draw()
┌──────────┐┌────────────┐┌────────────┐┌──────────┐
q_0: ─────■─────┤ RZ(θ[0]) ├┤0 ├┤0 ├┤ RZ(θ[3]) ├
┌────┴────┐├──────────┤│ RXX(θ[2]) ││ RYY(θ[2]) │├──────────┤
q_1: ┤ RY(0.2) ├┤ RZ(θ[1]) ├┤1 ├┤1 ├┤ RZ(θ[4]) ├
└─────────┘└──────────┘└────────────┘└────────────┘└──────────┘>>> ansatz = ExcitationPreserving(3, reps=1, mode='fsim', entanglement=[[0,2]],
... insert_barriers=True)
>>> print(ansatz)
┌──────────┐ ░ ┌────────────┐┌────────────┐ ░ ┌──────────┐
q_0: ┤ RZ(θ[0]) ├─░─┤0 ├┤0 ├─■──────░─┤ RZ(θ[5]) ├
├──────────┤ ░ │ ││ │ │ ░ ├──────────┤
q_1: ┤ RZ(θ[1]) ├─░─┤ RXX(θ[3]) ├┤ RYY(θ[3]) ├─┼──────░─┤ RZ(θ[6]) ├
├──────────┤ ░ │ ││ │ │θ[4] ░ ├──────────┤
q_2: ┤ RZ(θ[2]) ├─░─┤1 ├┤1 ├─■──────░─┤ RZ(θ[7]) ├
└──────────┘ ░ └────────────┘└────────────┘ ░ └──────────┘Create a new ExcitationPreserving 2-local circuit.
Parameters
- num_qubits (
Optional[int]) – The number of qubits of the ExcitationPreserving circuit. - mode (
str) – Choose the entangler mode, can be ‘iswap’ or ‘fsim’. - reps (
int) – Specifies how often the structure of a rotation layer followed by an entanglement layer is repeated. - entanglement (
Union[str,List[List[int]],Callable[[int],List[int]]]) – Specifies the entanglement structure. Can be a string (‘full’, ‘linear’ or ‘sca’), a list of integer-pairs specifying the indices of qubits entangled with one another, or a callable returning such a list provided with the index of the entanglement layer. See the Examples section ofTwoLocalfor more detail. - initial_state (
Optional[Any]) – A QuantumCircuit object to prepend to the circuit. - skip_unentangled_qubits (
bool) – If True, the single qubit gates are only applied to qubits that are entangled with another qubit. If False, the single qubit gates are applied to each qubit in the Ansatz. Defaults to False. - skip_unentangled_qubits – If True, the single qubit gates are only applied to qubits that are entangled with another qubit. If False, the single qubit gates are applied to each qubit in the Ansatz. Defaults to False.
- skip_final_rotation_layer (
bool) – If True, a rotation layer is added at the end of the ansatz. If False, no rotation layer is added. Defaults to True. - parameter_prefix (
str) – The parameterized gates require a parameter to be defined, for which we useParameterVector. - insert_barriers (
bool) – If True, barriers are inserted in between each layer. If False, no barriers are inserted.
Raises
ValueError – If the selected mode is not supported.
Attributes
ancillas
Returns a list of ancilla bits in the order that the registers were added.
Return type
List[AncillaQubit]
calibrations
Return calibration dictionary.
The custom pulse definition of a given gate is of the form {'gate_name': {(qubits, params): schedule}}
Return type
dict
clbits
data
entanglement
Get the entanglement strategy.
Return type
Union[str, List[str], List[List[str]], List[int], List[List[int]], List[List[List[int]]], List[List[List[List[int]]]], Callable[[int], str], Callable[[int], List[List[int]]]]
Returns
The entanglement strategy, see get_entangler_map() for more detail on how the format is interpreted.
entanglement_blocks
The blocks in the entanglement layers.
Return type
List[Instruction]
Returns
The blocks in the entanglement layers.
extension_lib
Default value: 'include "qelib1.inc";'
global_phase
header
Default value: 'OPENQASM 2.0;'
initial_state
Return the initial state that is added in front of the n-local circuit.
Return type
Returns
The initial state.
insert_barriers
If barriers are inserted in between the layers or not.
Return type
bool
Returns
True, if barriers are inserted in between the layers, False if not.
instances
Default value: 2308
metadata
The user provided metadata associated with the circuit
The metadata for the circuit is a user provided dict of metadata for the circuit. It will not be used to influence the execution or operation of the circuit, but it is expected to be passed between all transforms of the circuit (ie transpilation) and that providers will associate any circuit metadata with the results it returns from execution of that circuit.
Return type
dict
num_ancillas
Return the number of ancilla qubits.
Return type
int
num_clbits
Return number of classical bits.
Return type
int
num_layers
Return the number of layers in the n-local circuit.
Return type
int
Returns
The number of layers in the circuit.
num_parameters
Return type
int
num_parameters_settable
The number of total parameters that can be set to distinct values.
This does not change when the parameters are bound or exchanged for same parameters, and therefore is different from num_parameters which counts the number of unique Parameter objects currently in the circuit.
Return type
int
Returns
The number of parameters originally available in the circuit.
This quantity does not require the circuit to be built yet.
num_qubits
Returns the number of qubits in this circuit.
Return type
int
Returns
The number of qubits.
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.
Return type
List[int]
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.
ordered_parameters
The parameters used in the underlying circuit.
This includes float values and duplicates.
Examples
>>> # prepare circuit ...
>>> print(nlocal)
┌───────┐┌──────────┐┌──────────┐┌──────────┐
q_0: ┤ Ry(1) ├┤ Ry(θ[1]) ├┤ Ry(θ[1]) ├┤ Ry(θ[3]) ├
└───────┘└──────────┘└──────────┘└──────────┘
>>> nlocal.parameters
{Parameter(θ[1]), Parameter(θ[3])}
>>> nlocal.ordered_parameters
[1, Parameter(θ[1]), Parameter(θ[1]), Parameter(θ[3])]Return type
List[Parameter]
Returns
The parameters objects used in the circuit.
parameter_bounds
Return the parameter bounds.
Return type
List[Tuple[float, float]]
Returns
The parameter bounds.
parameters
Return type
ParameterView
preferred_init_points
The initial points for the parameters. Can be stored as initial guess in optimization.
Return type
Optional[List[float]]
Returns
The initial values for the parameters, or None, if none have been set.
prefix
Default value: 'circuit'
qregs
A list of the quantum registers associated with the circuit.
qubits
reps
The number of times rotation and entanglement block are repeated.
Return type
int
Returns
The number of repetitions.
rotation_blocks
The blocks in the rotation layers.
Return type
List[Instruction]
Returns
The blocks in the rotation layers.