"""
Copyright 2024 Entropica Labs Pte Ltd
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""
from __future__ import annotations
from typing import TypeVar
import numpy as np
from .pauli_array import PauliArray
from .pauli_computation import g_npfunc
# Dynamically bound type variable for PauliArray and its subclasses.
T = TypeVar("T", bound=PauliArray)
[docs]
def ndarray_rowsum(array: np.ndarray, h: int, i: int) -> np.ndarray:
"""
The rowsum function as described in Aaronson's paper for np.ndarray.
Reference: https://arxiv.org/abs/quant-ph/0406196
Parameters
----------
array : np.ndarray
The array representation of the PauliArray to be modified.
h : int
The row-index of the pauli string that will be modified.
i : int
The row-index of the pauli string that will be used.
Returns
-------
np.ndarray
The rowsum'ed array.
Raises
------
ValueError
If the rowsum value is odd.
"""
nqubits = array.shape[1] // 2
g_array = g_npfunc(
array[i, :nqubits],
array[i, nqubits : 2 * nqubits],
array[h, :nqubits],
array[h, nqubits : 2 * nqubits],
)
sum_g = np.sum(g_array)
lc_rowsum = 2 * array[h, 2 * nqubits] + 2 * array[i, 2 * nqubits] + sum_g
if lc_rowsum % 4 == 2:
array[h, 2 * nqubits] = 1
elif lc_rowsum % 4 == 0:
array[h, 2 * nqubits] = 0
else:
raise ValueError("rowsum cannot be odd!")
array[h, :-1] = array[i, :-1] ^ array[h, :-1]
return array
[docs]
def rowsum(pauli_array: T, h: int, i: int) -> T:
"""
The rowsum function as described in Aaronson's paper.
Reference: https://arxiv.org/abs/quant-ph/0406196
Parameters
----------
pauli_array : PauliArray
The PauliArray object to be modified.
h : int
The row-index of the pauli string that will be modified.
i : int
The row-index of the pauli string that will be used.
Returns
-------
PauliArray
The rowsum'ed PauliArray.
"""
pauli_array.array = ndarray_rowsum(pauli_array.array, h, i)
return pauli_array