def count_neighbors(qubits, qubit):
"""Counts the qubits that the given qubit can interact with."""
possibles = [
devices.GridQubit(qubit.row + 1, qubit.col),
devices.GridQubit(qubit.row - 1, qubit.col),
devices.GridQubit(qubit.row, qubit.col + 1),
devices.GridQubit(qubit.row, qubit.col - 1),
]
return len(list(e for e in possibles if e in qubits))
def _coupled_qubit_pairs(
qubits: List['cirq.GridQubit']) -> List[GridQubitPairT]:
pairs = []
qubit_set = set(qubits)
for qubit in qubits:
def add_pair(neighbor: 'cirq.GridQubit'):
if neighbor in qubit_set:
pairs.append((qubit, neighbor))
add_pair(devices.GridQubit(qubit.row, qubit.col + 1))
add_pair(devices.GridQubit(qubit.row + 1, qubit.col))
return pairs
def grid_qubit_from_proto_id(proto_id: str) -> 'cirq.GridQubit':
"""Parse a proto id to a `cirq.GridQubit`.
Proto ids for grid qubits are of the form `{row}_{col}` where `{row}` is
the integer row of the grid qubit, and `{col}` is the integer column of
the qubit.
Args:
proto_id: The id to convert.
Returns:
A `cirq.GridQubit` corresponding to the proto id.
Raises:
ValueError: If the string not of the correct format.
"""
match = re.match(GRID_QUBIT_ID_PATTERN, proto_id)
if match is None:
raise ValueError(
'GridQubit proto id must be of the form <int>_<int> but was {}'.
format(proto_id))
try:
row, col = match.groups()
return devices.GridQubit(row=int(row), col=int(col))
except ValueError:
raise ValueError(
'GridQubit proto id must be of the form <int>_<int> but was {}'.
format(proto_id))
def __contains__(self, pair) -> bool:
"""Checks whether a pair is in this layer."""
if self.vertical:
# Transpose row, col coords for vertical orientation.
a, b = pair
pair = devices.GridQubit(a.col, a.row), devices.GridQubit(b.col, b.row)
a, b = sorted(pair)
# qubits should be 1 column apart.
if (a.row != b.row) or (b.col != a.col + 1):
return False
# mod to get the position in the 2 x 2 unit cell with column offset.
pos = a.row % 2, (a.col - self.col_offset) % 2
return pos == (0, 0) or pos == (1, self.stagger)
def grid_qubit_from_proto_id(proto_id: str) -> 'cirq.GridQubit':
"""Parse a proto id to a `cirq.GridQubit`.
Proto ids for grid qubits are of the form `{row}_{col}` where `{row}` is
the integer row of the grid qubit, and `{col}` is the integer column of
the qubit.
Args:
proto_id: The id to convert.
Returns:
A `cirq.GridQubit` corresponding to the proto id.
Raises:
ValueError: If the string not of the correct format.
"""
parts = proto_id.split('_')
if len(parts) != 2:
raise ValueError(
'GridQubit proto id must be of the form <int>_<int> but was {}'.
format(proto_id))
try:
row, col = parts
return devices.GridQubit(row=int(row), col=int(col))
except ValueError:
raise ValueError(
'GridQubit proto id must be of the form <int>_<int> but was {}'.
format(proto_id))
def _make_cz_layer(qubits: Iterable[devices.GridQubit],
layer_index: int) -> Iterable[ops.Operation]:
"""
Each layer index corresponds to a shift/transpose of this CZ pattern:
●───● ● ● ●───● ● ● . . .
● ● ●───● ● ● ●───● . . .
●───● ● ● ●───● ● ● . . .
● ● ●───● ● ● ●───● . . .
●───● ● ● ●───● ● ● . . .
● ● ●───● ● ● ●───● . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
Labelled edges, showing the exact index-to-CZs mapping (mod 8):
●─0─●─2─●─4─●─6─●─0─. . .
3│ 7│ 3│ 7│ 3│
●─4─●─6─●─0─●─2─●─4─. . .
1│ 5│ 1│ 5│ 1│
●─0─●─2─●─4─●─6─●─0─. . .
7│ 3│ 7│ 3│ 7│
●─4─●─6─●─0─●─2─●─4─. . .
5│ 1│ 5│ 1│ 5│
●─0─●─2─●─4─●─6─●─0─. . .
3│ 7│ 3│ 7│ 3│
. . . . . .
. . . . . .
. . . . . .
Note that, for small devices, some layers will be empty because the layer
only contains edges not present on the device.
NOTE: This is the almost the function in supremacy.py,
but with a different order of CZ layers
"""
# map to an internal layer index to match the cycle order of public circuits
LAYER_INDEX_MAP = [0, 3, 2, 1, 4, 7, 6, 5]
internal_layer_index = LAYER_INDEX_MAP[layer_index % 8]
dir_row = internal_layer_index % 2
dir_col = 1 - dir_row
shift = (internal_layer_index >> 1) % 4
for q in qubits:
q2 = devices.GridQubit(q.row + dir_row, q.col + dir_col)
if q2 not in qubits:
continue # This edge isn't on the device.
if (q.row * (2 - dir_row) + q.col * (2 - dir_col)) % 4 != shift:
continue # No CZ along this edge for this layer.
yield ops.common_gates.CZ(q, q2)
def _make_cz_layer(device: google.XmonDevice, layer_index: int
) -> Iterable[cirq.Operation]:
"""
Each layer index corresponds to a shift/transpose of this CZ pattern:
●───● ● ● ●───● ● ● . . .
● ● ●───● ● ● ●───● . . .
●───● ● ● ●───● ● ● . . .
● ● ●───● ● ● ●───● . . .
●───● ● ● ●───● ● ● . . .
● ● ●───● ● ● ●───● . . .
. . . . . . . . .
. . . . . . . . .
. . . . . . . . .
Labelled edges, showing the exact index-to-CZs mapping (mod 8):
●─0─●─2─●─4─●─6─●─0─. . .
1│ 5│ 1│ 5│ 1│
●─4─●─6─●─0─●─2─●─4─. . .
3│ 7│ 3│ 7│ 3│
●─0─●─2─●─4─●─6─●─0─. . .
5│ 1│ 5│ 1│ 5│
●─4─●─6─●─0─●─2─●─4─. . .
7│ 3│ 7│ 3│ 7│
●─0─●─2─●─4─●─6─●─0─. . .
1│ 5│ 1│ 5│ 1│
. . . . . .
. . . . . .
. . . . . .
Note that, for small devices, some layers will be empty because the layer
only contains edges not present on the device.
"""
dir_row = layer_index % 2
dir_col = 1 - dir_row
shift = (layer_index >> 1) % 4
for q in device.qubits:
q2 = devices.GridQubit(q.row + dir_row, q.col + dir_col)
if q2 not in device.qubits:
continue # This edge isn't on the device.
if (q.row * (2 - dir_row) + q.col * (2 - dir_col)) % 4 != shift:
continue # No CZ along this edge for this layer.
yield google.Exp11Gate().on(q, q2)
def generate_boixo_2018_supremacy_circuits_v2_grid(
n_rows: int, n_cols: int, cz_depth: int, seed: int
) -> circuits.Circuit:
"""Generates Google Random Circuits v2 as in github.com/sboixo/GRCS cz_v2.
See also https://arxiv.org/abs/1807.10749
Args:
n_rows: number of rows of a 2D lattice.
n_cols: number of columns.
cz_depth: number of layers with CZ gates.
seed: seed for the random instance.
Returns:
A circuit corresponding to instance
inst_{n_rows}x{n_cols}_{cz_depth+1}_{seed}
The mapping of qubits is cirq.GridQubit(j,k) -> q[j*n_cols+k]
(as in the QASM mapping)
"""
qubits = [devices.GridQubit(i, j) for i in range(n_rows) for j in range(n_cols)]
return generate_boixo_2018_supremacy_circuits_v2(qubits, cz_depth, seed)
def _qubit_from_proto_dict(proto_dict):
"""Proto dict must have 'row' and 'col' keys."""
if 'row' not in proto_dict or 'col' not in proto_dict:
raise ValueError(
'Proto dict does not contain row or col: {}'.format(proto_dict))
return devices.GridQubit(row=proto_dict['row'], col=proto_dict['col'])
def test_cross_entropy_benchmarking():
# Check that the fidelities returned from a four-qubit XEB simulation are
# close to 1 (deviations from 1 is expected due to finite number of
# measurements).
simulator = sim.Simulator()
qubits = [
devices.GridQubit(0, 0),
devices.GridQubit(0, 1),
devices.GridQubit(1, 0),
devices.GridQubit(1, 1)
]
# Build a sequence of CZ gates.
interleaved_ops = build_entangling_layers(qubits, ops.CZ**0.91)
# Specify a set of single-qubit rotations. Pick prime numbers for the
# exponent to avoid evolving the system into a basis state.
single_qubit_rots = [[ops.X**0.37], [ops.Y**0.73, ops.X**0.53],
[ops.Z**0.61, ops.X**0.43], [ops.Y**0.19]]
# Simulate XEB using the default single-qubit gate set without two-qubit
# gates, XEB using the specified single-qubit gate set without two-qubit
# gates, and XEB using the specified single-qubit gate set with two-qubit
# gate. Check that the fidelities are close to 1.0 in all cases. Also,
# check that a single XEB fidelity is returned if a single cycle number
# is specified.
results_0 = cross_entropy_benchmarking(simulator,
qubits,
num_circuits=5,
repetitions=5000,
cycles=range(4, 30, 5))
results_1 = cross_entropy_benchmarking(
simulator,
qubits,
num_circuits=5,
repetitions=5000,
cycles=range(4, 30, 5),
scrambling_gates_per_cycle=single_qubit_rots)
results_2 = cross_entropy_benchmarking(
simulator,
qubits,
benchmark_ops=interleaved_ops,
num_circuits=5,
repetitions=5000,
cycles=range(4, 30, 5),
scrambling_gates_per_cycle=single_qubit_rots)
results_3 = cross_entropy_benchmarking(
simulator,
qubits,
benchmark_ops=interleaved_ops,
num_circuits=5,
repetitions=5000,
cycles=20,
scrambling_gates_per_cycle=single_qubit_rots)
fidelities_0 = [datum.xeb_fidelity for datum in results_0.data]
fidelities_1 = [datum.xeb_fidelity for datum in results_1.data]
fidelities_2 = [datum.xeb_fidelity for datum in results_2.data]
fidelities_3 = [datum.xeb_fidelity for datum in results_3.data]
assert np.isclose(np.mean(fidelities_0), 1.0, atol=0.1)
assert np.isclose(np.mean(fidelities_1), 1.0, atol=0.1)
assert np.isclose(np.mean(fidelities_2), 1.0, atol=0.1)
assert len(fidelities_3) == 1
# Sanity test that plot runs.
results_1.plot()
seed: seed for the random instance.
Returns:
A circuit corresponding to instance
inst_{n_rows}x{n_cols}_{cz_depth+1}_{seed}
The mapping of qubits is cirq.GridQubit(j,k) -> q[j*n_cols+k]
(as in the QASM mapping)
"""
qubits = [devices.GridQubit(i, j) for i in range(n_rows) for j in range(n_cols)]
return generate_boixo_2018_supremacy_circuits_v2(qubits, cz_depth, seed)
_bristlecone_qubits = frozenset(
{
devices.GridQubit(4, 8),
devices.GridQubit(2, 5),
devices.GridQubit(3, 2),
devices.GridQubit(5, 10),
devices.GridQubit(0, 6),
devices.GridQubit(4, 3),
devices.GridQubit(6, 7),
devices.GridQubit(8, 4),
devices.GridQubit(5, 5),
devices.GridQubit(4, 9),
devices.GridQubit(7, 8),
devices.GridQubit(8, 5),
devices.GridQubit(6, 2),
devices.GridQubit(7, 3),
devices.GridQubit(5, 0),
devices.GridQubit(4, 4),
def _qubit_from_proto(proto: operations_pb2.Qubit):
return devices.GridQubit(row=proto.row, col=proto.col)
