Update xmon gate times (#2952)

Author: dabacon

cirq/google/devices/known_devices.py

@@ -228,8 +228,8 @@ def _json_dict_(self) -> Dict[str, Any]:
 
 # Duration dict in picoseconds
 _DURATIONS_FOR_XMON = {
-    'cz': 50_000,
-    'xy': 20_000,
+    'cz': 45_000,
+    'xy': 15_000,
     'z': 0,
     'meas': 4_000_000,  # 1000ns for readout, 3000ns for "ring down"
 }

cirq/google/devices/known_devices_test.py

@@ -43,7 +43,7 @@ def test_foxtail_device_proto():
       name: "half_turns"
       type: FLOAT
     }
-    gate_duration_picos: 20000
+    gate_duration_picos: 15000
   }
   valid_gates {
     id: "z"
@@ -80,7 +80,7 @@ def test_foxtail_device_proto():
       name: "half_turns"
       type: FLOAT
     }
-    gate_duration_picos: 50000
+    gate_duration_picos: 45000
     valid_targets: "2_qubit_targets"
   }
   valid_gates {

cirq/google/devices/serializable_device_test.py

@@ -148,7 +148,7 @@ def test_duration_of():
         proto=cg.devices.known_devices.FOXTAIL_PROTO,
         gate_sets=[cg.gate_sets.XMON])
 
-    assert foxtail.duration_of(cirq.X(valid_qubit1)) == cirq.Duration(nanos=20)
+    assert foxtail.duration_of(cirq.X(valid_qubit1)) == cirq.Duration(nanos=15)
 
     # Unsupported op
     with pytest.raises(ValueError):