def __call__(self, U, *args, **kwargs):
circuit = self.Upre + U + self.Upost
objective = ExpectationValue(H=self.H, U=circuit)
Qp = paulis.Qp(U.qubits)
# get all overlaps
for i,Ux in enumerate(self.circuits):
S2 = ExpectationValue(H=Qp, U=circuit+Ux.dagger())
objective += numpy.abs(self.factors[i])*S2
return objective
def test_paulistring_sampling(backend, case):
print(case)
H = QubitHamiltonian.from_paulistrings(PauliString.from_string(case[0]))
U = gates.X(target=1) + gates.X(target=3) + gates.X(target=5)
E = ExpectationValue(H=H, U=U)
result = simulate(E,backend=backend, samples=1)
assert isclose(result, case[1], 1.e-4)
def compute_energy(self, method, *args, **kwargs):
"""
Call classical methods over PySCF (needs to be installed) or
use as a shortcut to calculate quantum energies (see make_upccgsd_ansatz)
Parameters
----------
method: method name
classical: HF, MP2, CCSD, CCSD(T), FCI
quantum: SPA-GASD (SPA can be dropped as well as letters in GASD)
examples: GSD is the same as UpCCGSD, SPA alone is equivalent to SPA-D
see make_upccgsd_ansatz of the this class for more information
args
kwargs
Returns
-------
"""
if any([x in method.upper() for x in ["U", "SPA", "PNO", "HCB"]]):
# simulate entirely in HCB representation if no singles are involved
if "S" not in method.upper().split("-")[-1] and "HCB" not in method.upper():
method = "HCB-"+method
U = self.make_upccgsd_ansatz(name=method)
if "hcb" in method.lower():
H = self.make_hardcore_boson_hamiltonian()
else:
H = self.make_hamiltonian()
E = ExpectationValue(H=H, U=U)
from tequila import minimize
return minimize(objective=E, *args, **kwargs).energy
else:
from tequila.quantumchemistry import INSTALLED_QCHEMISTRY_BACKENDS
if "pyscf" not in INSTALLED_QCHEMISTRY_BACKENDS:
raise TequilaMadnessException("PySCF needs to be installed to compute {}/MRA-PNO".format(method))
else:
from tequila.quantumchemistry import QuantumChemistryPySCF
molx = QuantumChemistryPySCF.from_tequila(self)
return molx.compute_energy(method=method)
def __call__(self, U, screening=False, *args, **kwargs):
return ExpectationValue(H=self.H, U=self.Upre + U + self.Upost, *args, **kwargs)