def test_basis_change(simulator):
for angle in list(uniform(0, 2 * pi, 5)):
EX = simulate(ExpectationValue(U=gates.Rx(target=0, angle=angle), H=PX(0)), backend=simulator)
EY = simulate(ExpectationValue(U=gates.Rx(target=0, angle=angle), H=PY(0)), backend=simulator)
EZ = simulate(ExpectationValue(U=gates.Rx(target=0, angle=angle), H=PZ(0)), backend=simulator)
EXX = simulate(ExpectationValue(U=gates.Rx(target=0, angle=angle) + change_basis(target=0, axis=0),
H=PZ(0)), backend=simulator)
EYY = simulate(ExpectationValue(U=gates.Rx(target=0, angle=angle) + change_basis(target=0, axis=1),
H=PZ(0)), backend=simulator)
EZZ = simulate(ExpectationValue(U=gates.Rx(target=0, angle=angle) + change_basis(target=0, axis=2),
H=PZ(0)), backend=simulator)
assert (isclose(EX, EXX, atol=1.e-4))
assert (isclose(EY, EYY, atol=1.e-4))
assert (isclose(EZ, EZZ, atol=1.e-4))
for i, gate in enumerate([gates.Rx, gates.Ry, gates.Rz]):
angle = uniform(0, 2 * pi)
U1 = gate(target=0, angle=angle)
U2 = change_basis(target=0, axis=i) + gates.Rz(target=0, angle=angle) + change_basis(target=0, axis=i,
daggered=True)
wfn1 = simulate(U1, backend=simulator)
wfn2 = simulate(U2, backend=simulator)
assert (isclose(numpy.abs(wfn1.inner(wfn2)) ** 2, 1.0, atol=1.e-4))
if simulator == "qiskit":
return # initial state not yet supported
wfn1 = simulate(U1, initial_state=1, backend=simulator)
wfn2 = simulate(U2, initial_state=1, backend=simulator)
assert (isclose(numpy.abs(wfn1.inner(wfn2)) ** 2, 1.0, atol=1.e-4))
def sample_paulistring(self, samples: int, paulistring, variables, *args,
**kwargs) -> numbers.Real:
"""
Sample an individual pauli word (pauli string) and return the average result thereof.
Parameters
----------
samples: int:
how many samples to evaluate.
paulistring:
the paulistring to be sampled.
args
kwargs
Returns
-------
float:
the average result of sampling the chosen paulistring
"""
not_in_u = [
q for q in paulistring.qubits if q not in self.abstract_qubits
]
reduced_ps = paulistring.trace_out_qubits(qubits=not_in_u)
if reduced_ps.coeff == 0.0:
return 0.0
if len(reduced_ps._data.keys()) == 0:
return reduced_ps.coeff
# make basis change and translate to backend
basis_change = QCircuit()
qubits = []
for idx, p in reduced_ps.items():
qubits.append(idx)
basis_change += change_basis(target=idx, axis=p)
# add basis change to the circuit
# deepcopy is necessary to avoid changing the circuits
# can be circumvented by optimizing the measurements
# on construction: tq.ExpectationValue(H=H, U=U, optimize_measurements=True)
circuit = self.create_circuit(circuit=copy.deepcopy(self.circuit),
abstract_circuit=basis_change)
# run simulators
counts = self.sample(samples=samples,
circuit=circuit,
read_out_qubits=qubits,
variables=variables,
*args,
**kwargs)
# compute energy
E = 0.0
n_samples = 0
for key, count in counts.items():
parity = key.array.count(1)
sign = (-1)**parity
E += sign * count
n_samples += count
assert n_samples == samples
E = E / samples * paulistring.coeff
return E
def sample_paulistring(self, samples: int, paulistring, *args,
**kwargs) -> numbers.Real:
# make basis change and translate to backend
basis_change = QCircuit()
not_in_u = [
] # all indices of the paulistring which are not part of the circuit i.e. will always have the same outcome
qubits = []
for idx, p in paulistring.items():
if idx not in self.abstract_qubit_map:
not_in_u.append(idx)
else:
qubits.append(idx)
basis_change += change_basis(target=idx, axis=p)
# check the constant parts as <0|pauli|0>, can only be 0 or 1
# so we can do a fast return of one of them is not Z
for i in not_in_u:
pauli = paulistring[i]
if pauli.upper() != "Z":
return 0.0
# make measurement instruction
measure = QCircuit()
if len(qubits) == 0:
# no measurement instructions for a constant term as paulistring
return paulistring.coeff
else:
measure += Measurement(target=qubits)
#measure += Measurement(name=str(paulistring), target=qubits)
circuit = self.circuit + self.create_circuit(basis_change +
measure)
# run simulators
counts = self.do_sample(samples=samples,
circuit=circuit,
*args,
**kwargs)
# compute energy
E = 0.0
n_samples = 0
for key, count in counts.items():
parity = key.array.count(1)
sign = (-1)**parity
E += sign * count
n_samples += count
E = E / samples * paulistring.coeff
return E
def sample_paulistring(self, samples: int, paulistring, variables, *args,
**kwargs):
"""
Has to be rewritten because of the pro-scription in qibo against calling already executed circuits.
Parameters
----------
samples: int:
how many samples to take.
paulistring: QubitHamiltonian:
the paulistring to sample.
variables: dict:
the variables to instantiate upon sampling.
args
kwargs
Returns
-------
"""
not_in_u = [
q for q in paulistring.qubits if q not in self.abstract_qubits
]
reduced_ps = paulistring.trace_out_qubits(qubits=not_in_u)
if reduced_ps.coeff == 0.0:
return 0.0
if len(reduced_ps._data.keys()) == 0:
return reduced_ps.coeff
# make basis change and translate to backend
basis_change = QCircuit()
qubits = []
for idx, p in reduced_ps.items():
qubits.append(idx)
basis_change += change_basis(target=idx, axis=p)
highest_qubit = max(paulistring.qubits)
new = self.rebuild_for_sample(abstract_circuit=basis_change,
variables=variables,
highest_qubit=highest_qubit)
# run simulators
counts = new.sample(samples=samples,
circuit=new.circuit,
read_out_qubits=qubits,
variables=variables,
*args,
**kwargs)
# compute energy
E = 0.0
n_samples = 0
#print('printing the counts')
#print(counts)
for key, count in counts.items():
parity = key.array.count(1)
sign = (-1)**parity
E += sign * count
n_samples += count
assert n_samples == samples
E = E / samples * paulistring.coeff
return E
