def convert_qubo_to_openfermion_ising(
qubo: BinaryQuadraticModel) -> IsingOperator:
"""Converts dimod BinaryQuadraticModel to OpenFermion IsingOperator object.
The resulting Openfermion IsingOperator has the following property:
For every bitstring, its expected value is the same as the energy of the original QUBO.
In order to ensure this, we had to add a minus sign for the coefficients
of the linear terms coming from dimod conversion.
For more context about conventions used please refer to note in `convert_measurements_to_sampleset` docstring.
Args:
qubo: Object we want to convert
Returns:
IsingOperator: IsingOperator representation of the input qubo.
"""
linear_coeffs, quadratic_coeffs, offset = qubo.to_ising()
list_of_ising_strings = [f"{offset}[]"]
for i, value in linear_coeffs.items():
list_of_ising_strings.append(f"{-value}[Z{i}]")
for (i, j), value in quadratic_coeffs.items():
list_of_ising_strings.append(f"{value}[Z{i} Z{j}]")
ising_string = " + ".join(list_of_ising_strings)
return IsingOperator(ising_string)
def convert_qubo_to_openfermion_ising(qubo: BinaryQuadraticModel):
"""Converts dimod BinaryQuadraticModel to OpenFermion IsingOperator object.
Args:
qubo: Object we want to convert
Returns:
IsingOperator: IsingOperator representation of the input qubo.
"""
linear_coeffs, quadratic_coeffs, offset = qubo.to_ising()
list_of_ising_strings = [f"{offset}[]"]
for i, value in linear_coeffs.items():
list_of_ising_strings.append(f"{value}[Z{i}]")
for (i, j), value in quadratic_coeffs.items():
list_of_ising_strings.append(f"{value}[Z{i} Z{j}]")
ising_string = " + ".join(list_of_ising_strings)
return IsingOperator(ising_string)
