Source code for qailab.circuit.encoding_blocks.rotational

 1"""R-gate implementations of input vector encoding blocks for variational circuits."""
 2from typing import Literal
 3from collections.abc import Callable
 4
 5from qiskit import QuantumCircuit
 6from qiskit.circuit.library import RealAmplitudes
 7
 8from qailab.circuit.base import EncodingBlock, EntanglingBlock
 9
10

[docs]
11class RotationalEncoder(EncodingBlock):
12    """
13    Encoding of input vector using rotational gates.
14
15    Attributes:
16        r_gate_type (Literal['x', 'y', 'z']): Type of rotational gate applied to each qubit.
17        block_type (Literal['input', 'weight']): Whether this block encodes weights or inputs.
18    """
19
20    def __init__(self, r_gate_type: Literal['x', 'y', 'z'], block_type: Literal['input', 'weight']) -> None:
21        self.r_gate_type: Literal['x', 'y', 'z'] = r_gate_type
22        super().__init__(f"R{r_gate_type}Encoder", block_type)
23
24    def _build_circuit(self, num_qubits: int) -> QuantumCircuit:
25        # Don't create new parameter vectors. This would enable the user to encode the same vector in different parts of the circuit.
26        if self._parameters is None:
27            self._parameters = self._create_parameters(num_qubits)
28
29        circuit = QuantumCircuit(num_qubits)
30        match self.r_gate_type:
31            case 'x':
32                fn = circuit.rx
33            case 'y':
34                fn = circuit.ry
35            case 'z':
36                fn = circuit.rz
37            case _:
38                raise ValueError(f"'{self.r_gate_type}' is not a valid rotational gate type")
39        for i in range(num_qubits):
40            fn(self._parameters[i], i)
41
42        return circuit

43
44

[docs]
45class RealAmplitudesBlock(EncodingBlock, EntanglingBlock):
46    """
47    Block wrapper for RealAmplitudes from qiskit.circuit.library
48    """
49
50    def __init__(
51        self,
52        block_type: Literal['input', 'weight'],
53        entanglement: str | list[list[int]] | Callable[[int], list[int]] = "reverse_linear",
54        reps: int = 3,
55        skip_final_rotation_layer: bool = False
56    ) -> None:
57        self.entanglement = entanglement
58        self.reps = reps
59        self.skip_final_rotation_layer = skip_final_rotation_layer
60        super().__init__("RealAmplitudesEncoder", block_type)
61
62    def _build_circuit(self, num_qubits: int) -> QuantumCircuit:
63        pv_name = self._create_parameters(1)[0].name
64        amplitudes = RealAmplitudes(
65            num_qubits,
66            parameter_prefix=pv_name,
67            entanglement=self.entanglement,
68            reps=self.reps,
69            skip_final_rotation_layer=self.skip_final_rotation_layer,
70        )
71        self._parameters = list(amplitudes.parameters)
72        return amplitudes