Quantum Volume: Add the ability to specify the device graph to compil…

…e the model circuit onto (#2645)

This should give us the ability to try different parts of the device to find the optimal configuration. Note that the qubits that were used are already returned in the QuantumVolumeResult.compiled_circuit property.

@mpharrigan

cirq/contrib/quantum_volume/quantum_volume.py

@@ -2,11 +2,12 @@
 https://arxiv.org/abs/1811.12926.
 """
 
-from typing import Optional, List, cast, Callable, Dict, Tuple, Set
+from typing import Optional, List, cast, Callable, Dict, Tuple, Set, Union
 from dataclasses import dataclass
 
 import numpy as np
 import pandas as pd
+import networkx as nx
 
 import cirq
 import cirq.contrib.routing as ccr
@@ -219,14 +220,14 @@ def optimization_at(self, circuit: cirq.Circuit, index: int,
 def compile_circuit(
         circuit: cirq.Circuit,
         *,
-        device: cirq.google.XmonDevice,
+        device_graph: nx.Graph,
         routing_attempts: int,
         compiler: Callable[[cirq.Circuit], cirq.Circuit] = None,
         routing_algo_name: Optional[str] = None,
         router: Optional[Callable[..., ccr.SwapNetwork]] = None,
         add_readout_error_correction=False,
 ) -> CompilationResult:
-    """Compile the given model circuit onto the given device. This uses a
+    """Compile the given model circuit onto the given device graph. This uses a
     different compilation method than described in
     https://arxiv.org/pdf/1811.12926.pdf Appendix A. The latter goes through a
     7-step process involving various decompositions, routing, and optimization
@@ -235,7 +236,7 @@ def compile_circuit(
 
     Args:
         circuit: The model circuit to compile.
-        device: The device to compile onto.
+        device_graph: The device graph to compile onto.
         routing_attempts: See doc for calculate_quantum_volume.
         compiler: An optional function to deconstruct the model circuit's
             gates down to the target devices gate set and then optimize it.
@@ -278,7 +279,7 @@ def compile_circuit(
     swap_networks: List[ccr.SwapNetwork] = []
     for _ in range(routing_attempts):
         swap_network = ccr.route_circuit(compiled_circuit,
-                                         ccr.xmon_device_to_graph(device),
+                                         device_graph,
                                          router=router,
                                          algo_name=routing_algo_name)
         swap_networks.append(swap_network)
@@ -365,7 +366,7 @@ def prepare_circuits(
 
 def execute_circuits(
         *,
-        device: cirq.google.XmonDevice,
+        device_graph: nx.Graph,
         samplers: List[cirq.Sampler],
         circuits: List[Tuple[cirq.Circuit, List[int]]],
         routing_attempts: int,
@@ -376,7 +377,7 @@ def execute_circuits(
     """Executes the given circuits on the given samplers.
 
     Args
-        device: The device to run the compiled circuit on.
+        device_graph: The device graph to run the compiled circuit on.
         samplers: The samplers to run the algorithm on.
         circuits: The circuits to sample from.
         routing_attempts: See doc for calculate_quantum_volume.
@@ -399,7 +400,7 @@ def execute_circuits(
         compiled_circuits.append(
             compile_circuit(
                 model_circuit,
-                device=device,
+                device_graph=device_graph,
                 compiler=compiler,
                 routing_attempts=routing_attempts,
                 add_readout_error_correction=add_readout_error_correction))
@@ -429,7 +430,7 @@ def calculate_quantum_volume(
         num_qubits: int,
         depth: int,
         num_circuits: int,
-        device: cirq.google.XmonDevice,
+        device_or_qubits: Union[cirq.google.XmonDevice, List[cirq.GridQubit]],
         samplers: List[cirq.Sampler],
         random_state: cirq.value.RANDOM_STATE_LIKE = None,
         compiler: Callable[[cirq.Circuit], cirq.Circuit] = None,
@@ -451,7 +452,8 @@ def calculate_quantum_volume(
         depth: The number of gate layers to generate.
         num_circuits: The number of random circuits to run.
         random_state: Random state or random state seed.
-        device: The device to run the compiled circuit on.
+        device_or_qubits: The device or the device qubits to run the compiled
+            circuit on.
         samplers: The samplers to run the algorithm on.
         compiler: An optional function to compiler the model circuit's
             gates down to the target devices gate set and the optimize it.
@@ -474,9 +476,17 @@ def calculate_quantum_volume(
                                 depth=depth,
                                 num_circuits=num_circuits,
                                 random_state=random_state)
+
+    # Get the device graph from the given qubits or device.
+    device_graph = None
+    if isinstance(device_or_qubits, list):
+        device_graph = ccr.gridqubits_to_graph_device(device_or_qubits)
+    else:
+        device_graph = ccr.xmon_device_to_graph(device_or_qubits)
+
     return execute_circuits(
         circuits=circuits,
-        device=device,
+        device_graph=device_graph,
         compiler=compiler,
         samplers=samplers,
         repetitions=repetitions,

cirq/contrib/quantum_volume/quantum_volume_test.py

@@ -116,10 +116,11 @@ def test_sample_heavy_set_with_parity():
 def test_compile_circuit_router():
     """Tests that the given router is used."""
     router_mock = MagicMock()
-    cirq.contrib.quantum_volume.compile_circuit(cirq.Circuit(),
-                                                device=cirq.google.Bristlecone,
-                                                router=router_mock,
-                                                routing_attempts=1)
+    cirq.contrib.quantum_volume.compile_circuit(
+        cirq.Circuit(),
+        device_graph=ccr.xmon_device_to_graph(cirq.google.Bristlecone),
+        router=router_mock,
+        routing_attempts=1)
     router_mock.assert_called()
 
 
@@ -132,7 +133,7 @@ def test_compile_circuit():
     ])
     compilation_result = cirq.contrib.quantum_volume.compile_circuit(
         model_circuit,
-        device=cirq.google.Bristlecone,
+        device_graph=ccr.xmon_device_to_graph(cirq.google.Bristlecone),
         compiler=compiler_mock,
         routing_attempts=1)
 
@@ -156,7 +157,7 @@ def test_compile_circuit_replaces_swaps():
     ])
     compilation_result = cirq.contrib.quantum_volume.compile_circuit(
         model_circuit,
-        device=cirq.google.Bristlecone,
+        device_graph=ccr.xmon_device_to_graph(cirq.google.Bristlecone),
         compiler=compiler_mock,
         routing_attempts=1)
 
@@ -186,7 +187,7 @@ def test_compile_circuit_with_readout_correction():
     ])
     compilation_result = cirq.contrib.quantum_volume.compile_circuit(
         model_circuit,
-        device=cirq.google.Bristlecone,
+        device_graph=ccr.xmon_device_to_graph(cirq.google.Bristlecone),
         compiler=compiler_mock,
         router=router_mock,
         routing_attempts=1,
@@ -226,7 +227,7 @@ def test_compile_circuit_multiple_routing_attempts():
 
     compilation_result = cirq.contrib.quantum_volume.compile_circuit(
         model_circuit,
-        device=cirq.google.Bristlecone,
+        device_graph=ccr.xmon_device_to_graph(cirq.google.Bristlecone),
         compiler=compiler_mock,
         router=router_mock,
         routing_attempts=3)
@@ -245,7 +246,9 @@ def test_compile_circuit_no_routing_attempts():
 
     with pytest.raises(AssertionError) as e:
         cirq.contrib.quantum_volume.compile_circuit(
-            model_circuit, device=cirq.google.Bristlecone, routing_attempts=0)
+            model_circuit,
+            device_graph=ccr.xmon_device_to_graph(cirq.google.Bristlecone),
+            routing_attempts=0)
     assert e.match('Unable to get routing for circuit')
 
 
@@ -255,7 +258,7 @@ def test_calculate_quantum_volume_result():
         num_qubits=3,
         depth=3,
         num_circuits=1,
-        device=cirq.google.Bristlecone,
+        device_or_qubits=cirq.google.Bristlecone,
         samplers=[cirq.Simulator()],
         routing_attempts=2,
         random_state=1,
@@ -273,6 +276,26 @@ def test_calculate_quantum_volume_result():
     cirq.to_json(results, buffer)
 
 
+def test_calculate_quantum_volume_result_with_device_graph():
+    """Test that running the main loop routes the circuit onto the given device
+       graph"""
+    device_qubits = [cirq.GridQubit(i, j) for i in range(2) for j in range(3)]
+    results = cirq.contrib.quantum_volume.calculate_quantum_volume(
+        num_qubits=3,
+        depth=3,
+        num_circuits=1,
+        device_or_qubits=device_qubits,
+        samplers=[cirq.Simulator()],
+        routing_attempts=2,
+        random_state=1,
+    )
+
+    assert len(results) == 1
+    assert ccr.ops_are_consistent_with_device_graph(
+        results[0].compiled_circuit.all_operations(),
+        ccr.get_grid_device_graph(2, 3))
+
+
 def test_calculate_quantum_volume_loop():
     """Test that calculate_quantum_volume is able to run without erring."""
     # Keep test from taking a long time by lowering circuits and routing
@@ -283,7 +306,7 @@ def test_calculate_quantum_volume_loop():
         num_circuits=1,
         routing_attempts=2,
         random_state=1,
-        device=cirq.google.Bristlecone,
+        device_or_qubits=cirq.google.Bristlecone,
         samplers=[cirq.Simulator()])
 
 
@@ -298,6 +321,6 @@ def test_calculate_quantum_volume_loop_with_readout_correction():
         num_circuits=1,
         routing_attempts=2,
         random_state=1,
-        device=cirq.google.Bristlecone,
+        device_or_qubits=cirq.google.Bristlecone,
         samplers=[cirq.Simulator()],
         add_readout_error_correction=True)

examples/advanced/quantum_volume.py

@@ -47,7 +47,7 @@ def main(*, num_qubits: int, depth: int, num_circuits: int, seed: int):
                              depth=depth,
                              num_circuits=num_circuits,
                              random_state=seed,
-                             device=device,
+                             device_or_qubits=device,
                              samplers=[cirq.Simulator(), noisy],
                              compiler=compiler)