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Fix of sly bug in low-depth simulation with certain onsite interactions #143

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Merged
babbush merged 3 commits into from
Aug 15, 2017
Merged

Fix of sly bug in low-depth simulation with certain onsite interactions #143

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70b6103
Merge remote-tracking branch 'ProjectQ-Framework/develop' into develop
Aug 15, 2017
6f39320
Fix of sly bug in low-depth simulation with onsite interaction
Aug 15, 2017
bb29ecc
Merge remote-tracking branch 'ProjectQ-Framework/develop' into simula…
Aug 15, 2017
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14 changes: 9 additions & 5 deletions src/fermilib/circuits/_low_depth_trotter_simulation.py
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Original file line number Diff line number Diff line change
Expand Up @@ -144,22 +144,26 @@ def simulation_gate_trotter_step(register, hamiltonian, input_ordering=None,
# Divide by two for second order Trotter.
if not first_order:
z_angle /= 2.
Rz(z_angle) | register[i]
# After special_F_adjacent, qubits i and i+1 have swapped;
# the ith rotation must thus be applied to qubit i+1.
Rz(z_angle) | register[i + 1]
Ph(z_angle / 2.) | register

num_operator_right = ((input_ordering[i + 1], 1),
(input_ordering[i + 1], 0))
num_operator_right = ((input_ordering[i+1], 1),
(input_ordering[i+1], 0))
if num_operator_right in hamiltonian.terms:
# Jordan-Wigner maps a number term c*n_i to c*(I-Z_i)/2.
# Time evolution is then exp(-i c*(I-Z_i)/2), which is equal to
# a phase exp(-ic/2) and a rotation Rz(-c).
z_angle = (-hamiltonian.terms[num_operator_left] /
z_angle = (-hamiltonian.terms[num_operator_right] /
(n_qubits - 1))

# Divide by two for second order Trotter.
if not first_order:
z_angle /= 2
Rz(z_angle) | register[i + 1]
# After special_F_adjacent, qubits i and i+1 have swapped;
# the (i+1)th rotation must thus be applied to qubit i.
Rz(z_angle) | register[i]
Ph(z_angle / 2.) | register

# Finally, swap the two modes in input_ordering.
Expand Down
110 changes: 101 additions & 9 deletions src/fermilib/circuits/_low_depth_trotter_simulation_test.py
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Original file line number Diff line number Diff line change
Expand Up @@ -96,7 +96,9 @@ def test_simulate_n0n1(self):
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T))
expected.T),
msg=str(ordered_wavefunction(self.engine) -
expected.T))

def test_simulate_n0n3(self):
hamiltonian = FermionOperator('3^ 0^ 3 0')
Expand All @@ -114,7 +116,9 @@ def test_simulate_n0n3(self):
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T))
expected.T),
msg=str(ordered_wavefunction(self.engine) -
expected.T))

def test_simulate_n1n3(self):
hamiltonian = FermionOperator('3^ 1^ 3 1')
Expand All @@ -132,7 +136,9 @@ def test_simulate_n1n3(self):
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T))
expected.T),
msg=str(ordered_wavefunction(self.engine) -
expected.T))

def test_single_trotter_step_no_input_ordering_n1n3(self):
hamiltonian = FermionOperator('3^ 1^ 3 1')
Expand All @@ -150,7 +156,9 @@ def test_single_trotter_step_no_input_ordering_n1n3(self):
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T))
expected.T),
msg=str(ordered_wavefunction(self.engine) -
expected.T))

def test_simulate_hopping_0_to_1(self):
hamiltonian = FermionOperator('1^ 0') + FermionOperator('0^ 1')
Expand All @@ -169,7 +177,9 @@ def test_simulate_hopping_0_to_1(self):
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T))
expected.T),
msg=str(ordered_wavefunction(self.engine) -
expected.T))

def test_simulate_hopping_1_to_3(self):
hamiltonian = FermionOperator('1^ 3') + FermionOperator('3^ 1')
Expand Down Expand Up @@ -236,7 +246,7 @@ def test_simulate_multiple_hopping_terms(self):
self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T, atol=1e-2))

def test_simulate_multiple_number_terms(self):
def test_simulate_multiple_two_number_terms(self):
hamiltonian = (0.37 * FermionOperator('1^ 0^ 1 0') +
2.4 * FermionOperator('3^ 0^ 3 0') -
2 * FermionOperator('3^ 1^ 3 1'))
Expand All @@ -259,7 +269,42 @@ def test_simulate_multiple_number_terms(self):
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T))
expected.T),
msg=str(numpy.array(ordered_wavefunction(self.engine) -
expected.T)))

def test_simulate_single_and_double_number_terms(self):
hamiltonian = (0.37 * FermionOperator('1^ 0^ 1 0') +
2.4 * FermionOperator('3^ 0^ 3 0') -
2 * FermionOperator('3^ 1^ 3 1') +
1.1 * FermionOperator('2^ 2') +
1.7 * FermionOperator('0^ 0') -
0.3 * FermionOperator('3^ 3'))

projectq.ops.All(projectq.ops.H) | self.register

_low_depth_trotter_simulation.simulate_dual_basis_evolution(
self.register, hamiltonian, trotter_steps=1, first_order=False)

self.engine.flush()

# get_sparse_operator reverses the indices, so reverse the sites
# the Hamiltonian acts on so as to compare them.
reversed_operator = (0.37 * FermionOperator('3^ 2^ 3 2') +
2.4 * FermionOperator('3^ 0^ 3 0') -
2 * FermionOperator('2^ 0^ 2 0') +
1.1 * FermionOperator('1^ 1') +
1.7 * FermionOperator('3^ 3') -
0.3 * FermionOperator('0^ 0'))
evol_matrix = expm(-1j * get_sparse_operator(
reversed_operator, n_qubits=self.size)).todense()
expected = evol_matrix * numpy.matrix([2 ** (-self.size / 2.)] *
2 ** self.size).T

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T),
msg=str(numpy.array(ordered_wavefunction(self.engine) -
expected.T)))

def test_simulate_overlapping_number_and_hopping_terms(self):
hamiltonian = (0.37 * FermionOperator('1^ 0^ 1 0') +
Expand All @@ -283,7 +328,9 @@ def test_simulate_overlapping_number_and_hopping_terms(self):

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T,
atol=1e-2))
atol=1e-2),
msg=str(numpy.array(ordered_wavefunction(self.engine) -
expected.T)))

def test_simulate_dual_basis_hamiltonian(self):
hamiltonian = dual_basis_hamiltonian(1, self.size)
Expand Down Expand Up @@ -313,7 +360,52 @@ def test_simulate_dual_basis_hamiltonian(self):

self.assertTrue(numpy.allclose(ordered_wavefunction(self.engine),
expected.T,
atol=1e-2))
atol=1e-2),
msg=str(numpy.array(ordered_wavefunction(self.engine) -
expected.T)))

def test_simulate_dual_basis_hamiltonian_with_spin_and_potentials(self):
big_eng = projectq.MainEngine()
big_reg = big_eng.allocate_qureg(2 * self.size)
hamiltonian = dual_basis_hamiltonian(1, self.size, spinless=False)

for i in range(2 * self.size):
coefficient = 1. / (i + 1)
if i % 3:
coefficient = -coefficient
hamiltonian += FermionOperator(((i, 1), (i, 0)), coefficient)

# Choose random state.
initial_state = numpy.zeros(2 ** (2 * self.size), dtype=complex)
for i in range(len(initial_state)):
initial_state[i] = (random.random() *
numpy.exp(1j * 2 * numpy.pi * random.random()))
initial_state /= numpy.linalg.norm(initial_state)

# Put randomly chosen state in the registers.
big_eng.flush()
big_eng.backend.set_wavefunction(initial_state, big_reg)

_low_depth_trotter_simulation.simulate_dual_basis_evolution(
big_reg, hamiltonian, trotter_steps=7, first_order=False,
input_ordering=list(range(7, -1, -1)))

big_eng.flush()

# get_sparse_operator reverses the indices - we've accounted for this
# with the reversed input_ordering.
evol_matrix = expm(-1j * get_sparse_operator(
hamiltonian, n_qubits=2*self.size)).todense()
initial_state = numpy.matrix(initial_state).T
expected = evol_matrix * initial_state

self.assertTrue(numpy.allclose(ordered_wavefunction(big_eng),
expected.T,
atol=1e-2),
msg=str(numpy.array(ordered_wavefunction(big_eng) -
expected.T)))

projectq.ops.All(projectq.ops.Measure) | big_reg

def test_simulate_dual_basis_evolution_bad_input_ordering(self):
with self.assertRaises(ValueError):
Expand Down