Source code for qlauncher.hampy.utils

 1"""
 2Utility functions for Hampy objects.
 3"""
 4
 5from qiskit.quantum_info import Pauli, SparsePauliOp
 6
 7from qlauncher.hampy.object import Equation
 8
 9

[docs]
10def shift_affected_qubits(equation: Equation, shift: int) -> Equation:
11    """
12    Shifts the qubits affected by the equation by the given amount, wrapping around if the index goes out of bounds.
13
14    For each Pauli in the equation hamiltonian, shifts the Pauli string by the given amount.
15    i.e (shift = 1) IZIZ -> ZIZI, etc. !Might be unwanted! ZIII -> IIIZ
16    Keeps the coefficients the same.
17
18    Args:
19            equation: Equation to shift
20            shift: Amount to shift by
21
22    Returns:
23            Equation: New equation affecting the shifted qubits
24    """
25    op = equation.hamiltonian
26
27    if shift == 0:
28        return equation
29
30    n_paulis = []
31    n_coeffs = []
32
33    for p_string, coeff in op.label_iter():
34        p_string = p_string[shift:] + p_string[:shift]
35        n_paulis.append(Pauli(data=p_string))
36        n_coeffs.append(coeff)
37
38    new_op = SparsePauliOp(n_paulis, coeffs=n_coeffs)
39
40    return Equation(new_op)