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

[docs]
 8def shift_affected_qubits(equation: Equation, shift: int) -> Equation:
 9    """
10    Shifts the qubits affected by the equation by the given amount, wrapping around if the index goes out of bounds.
11
12    For each Pauli in the equation hamiltonian, shifts the Pauli string by the given amount.
13    i.e (shift = 1) IZIZ -> ZIZI, etc. !Might be unwanted! ZIII -> IIIZ
14    Keeps the coefficients the same.
15
16    Args:
17        equation: Equation to shift
18        shift: Amount to shift by
19
20    Returns:
21        Equation: New equation affecting the shifted qubits
22    """
23    op = equation.hamiltonian
24
25    if shift == 0:
26        return equation
27
28    npaulis = []
29    ncoeffs = []
30
31    for p_string, coeff in op.label_iter():
32        p_string = p_string[shift:] + p_string[:shift]
33        npaulis.append(Pauli(data=p_string))
34        ncoeffs.append(coeff)
35
36    new_op = SparsePauliOp(npaulis, coeffs=ncoeffs)
37
38    return Equation(new_op)