1414
1515"""An optimization pass that pushes Z gates later and later in the circuit."""
1616
17- from typing import cast , Dict , Iterable , List , Optional , Tuple
18- from collections import defaultdict
19- import numpy as np
20- import sympy
17+ from cirq import circuits , transformers
2118
22- from cirq import circuits , ops , protocols
23- from cirq .transformers .analytical_decompositions import single_qubit_decompositions
24-
25-
26- def _is_integer (n ):
27- return np .isclose (n , np .round (n ))
28-
29-
30- def _is_swaplike (op : ops .Operation ):
31- if isinstance (op .gate , ops .SwapPowGate ):
32- return op .gate .exponent == 1
33-
34- if isinstance (op .gate , ops .ISwapPowGate ):
35- return _is_integer ((op .gate .exponent - 1 ) / 2 )
36-
37- if isinstance (op .gate , ops .FSimGate ):
38- return _is_integer (op .gate .theta / np .pi - 1 / 2 )
39-
40- return False
19+ # from cirq.transformers import eject_z
20+ from cirq ._compat import deprecated_class
4121
4222
23+ @deprecated_class (deadline = 'v1.0' , fix = 'Use cirq.eject_z instead.' )
4324class EjectZ :
4425 """Pushes Z gates towards the end of the circuit.
4526
@@ -62,96 +43,8 @@ def __init__(self, tolerance: float = 0.0, eject_parameterized: bool = False) ->
6243 self .eject_parameterized = eject_parameterized
6344
6445 def optimize_circuit (self , circuit : circuits .Circuit ):
65- # Tracks qubit phases (in half turns; multiply by pi to get radians).
66- qubit_phase : Dict [ops .Qid , float ] = defaultdict (lambda : 0 )
67- deletions : List [Tuple [int , ops .Operation ]] = []
68- replacements : List [Tuple [int , ops .Operation , ops .Operation ]] = []
69- insertions : List [Tuple [int , ops .Operation ]] = []
70- phased_xz_replacements : Dict [Tuple [int , ops .Qid ], int ] = {}
71-
72- def dump_tracked_phase (qubits : Iterable [ops .Qid ], index : int ) -> None :
73- """Zeroes qubit_phase entries by emitting Z gates."""
74- for q in qubits :
75- p = qubit_phase [q ]
76- qubit_phase [q ] = 0
77- if single_qubit_decompositions .is_negligible_turn (p , self .tolerance ):
78- continue
79- dumped = False
80- moment_index = circuit .prev_moment_operating_on ([q ], index )
81- if moment_index is not None :
82- op = circuit .moments [moment_index ][q ]
83- if op and isinstance (op .gate , ops .PhasedXZGate ):
84- # Attach z-rotation to replacing PhasedXZ gate.
85- idx = phased_xz_replacements [moment_index , q ]
86- _ , _ , repl_op = replacements [idx ]
87- gate = cast (ops .PhasedXZGate , repl_op .gate )
88- repl_op = gate .with_z_exponent (p * 2 ).on (q )
89- replacements [idx ] = (moment_index , op , repl_op )
90- dumped = True
91- if not dumped :
92- # Add a new Z gate
93- dump_op = ops .Z (q ) ** (p * 2 )
94- insertions .append ((index , dump_op ))
95-
96- for moment_index , moment in enumerate (circuit ):
97- for op in moment .operations :
98- # Move Z gates into tracked qubit phases.
99- h = _try_get_known_z_half_turns (op , self .eject_parameterized )
100- if h is not None :
101- q = op .qubits [0 ]
102- qubit_phase [q ] += h / 2
103- deletions .append ((moment_index , op ))
104- continue
105-
106- # Z gate before measurement is a no-op. Drop tracked phase.
107- if isinstance (op .gate , ops .MeasurementGate ):
108- for q in op .qubits :
109- qubit_phase [q ] = 0
110-
111- # If there's no tracked phase, we can move on.
112- phases = [qubit_phase [q ] for q in op .qubits ]
113- if not isinstance (op .gate , ops .PhasedXZGate ) and all (
114- single_qubit_decompositions .is_negligible_turn (p , self .tolerance )
115- for p in phases
116- ):
117- continue
118-
119- if _is_swaplike (op ):
120- a , b = op .qubits
121- qubit_phase [a ], qubit_phase [b ] = qubit_phase [b ], qubit_phase [a ]
122- continue
123-
124- # Try to move the tracked phasing over the operation.
125- phased_op = op
126- for i , p in enumerate (phases ):
127- if not single_qubit_decompositions .is_negligible_turn (p , self .tolerance ):
128- phased_op = protocols .phase_by (phased_op , - p , i , default = None )
129- if phased_op is not None :
130- gate = phased_op .gate
131- if isinstance (gate , ops .PhasedXZGate ) and (
132- self .eject_parameterized or not protocols .is_parameterized (gate .z_exponent )
133- ):
134- qubit = phased_op .qubits [0 ]
135- qubit_phase [qubit ] += gate .z_exponent / 2
136- phased_op = gate .with_z_exponent (0 ).on (qubit )
137- repl_idx = len (replacements )
138- phased_xz_replacements [moment_index , qubit ] = repl_idx
139- replacements .append ((moment_index , op , phased_op ))
140- else :
141- dump_tracked_phase (op .qubits , moment_index )
142-
143- dump_tracked_phase (qubit_phase .keys (), len (circuit ))
144- circuit .batch_remove (deletions )
145- circuit .batch_replace (replacements )
146- circuit .batch_insert (insertions )
147-
148-
149- def _try_get_known_z_half_turns (op : ops .Operation , eject_parameterized : bool ) -> Optional [float ]:
150- if not isinstance (op , ops .GateOperation ):
151- return None
152- if not isinstance (op .gate , ops .ZPowGate ):
153- return None
154- h = op .gate .exponent
155- if not eject_parameterized and isinstance (h , sympy .Basic ):
156- return None
157- return h
46+ circuit ._moments = [
47+ * transformers .eject_z (
48+ circuit , atol = self .tolerance , eject_parameterized = self .eject_parameterized
49+ )
50+ ]
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