cirq_google.ops.FSimGateFamily

GateFamily useful to convert/accept cirq.FSimGate and other related gate types.

This gate family is useful to work with any of the different representations of cirq.FSimGate and its related types present in Cirq. Specifically, the gate family can be used to convert or accept (if possible) compatible instances of any of the following POSSIBLE_FSIM_GATES types:

  1. cirq.FSimGate, cirq.PhasedFSimGate
  2. cirq.ISwapPowGate, cirq.PhasedISwapPowGate
  3. cirq.CZPowGate
  4. cirq.IdentityGate

The gate family also allows an option to accept parameterized gates, assuming that the correct parameters would eventually be filled.

For example,

  1. To convert to/from any of the non-parameterized POSSIBLE_FSIM_GATES types:
>>> gf = cirq_google.FSimGateFamily()
>>> assert gf.convert(cirq.FSimGate(np.pi/4, 0), cirq.ISwapPowGate) == cirq.SQRT_ISWAP_INV
>>> assert gf.convert(cirq.PhasedFSimGate(0, 0, 0, 0, np.pi), cirq.CZPowGate) == cirq.CZ
>>> assert gf.convert(cirq.FSimGate(-np.pi/2, sympy.Symbol("t")), cirq.ISwapPowGate) is None
  1. To convert to/from any of the parameterized POSSIBLE_FSIM_GATES types (assuming correct value of the parameter would be filled in during paramter resolution):
>>> gf = cirq_google.FSimGateFamily(allow_symbols = True)
>>> theta, phi = sympy.Symbol("theta"), sympy.Symbol("phi")
>>> assert gf.convert(cirq.FSimGate(-np.pi/4, phi), cirq.ISwapPowGate) == cirq.SQRT_ISWAP
>>> assert gf.convert(cirq.PhasedFSimGate(theta, 0, 0, 0, np.pi), cirq.CZPowGate) == cirq.CZ
>>> assert gf.convert(cirq.FSimGate(theta, phi), cirq.IdentityGate) == cirq.IdentityGate(2)
  1. To accept instances of gate_types_to_check based on type / value equality check against gates in gates_to_accept, possibly accepting parameterized instances (assuming correct parameter value would be filled in during parameter resolution) based on allow_symbols:
>>> gf = cirq_google.FSimGateFamily(
>>>     gates_to_accept=[cirq.SQRT_ISWAP, cirq.CZPowGate, cirq_google.SYC],
>>>     gate_types_to_check=[cirq.FSimGate],
>>>     allow_symbols=True,
>>> )
>>> theta, phi = sympy.Symbol("theta"), sympy.Symbol("phi")
>>> assert cirq.FSimGate(theta, phi) in gf # Assumes correct theta/phi will be substituted.
>>> assert cirq_google.SYC in gf # SYC
>>> assert cirq.FSimGate(0, np.pi / 2) in gf # CZPowGate
>>> assert cirq.FSimGate(-np.pi / 4, phi) in gf # SQRT_ISWAP
>>> assert cirq.FSimGate(-np.pi / 8, phi) not in gf # No value of `phi` would make it equal to
>>>                                                 # any gate/gate type in `gates_to_accept`.
>>> assert cirq.CZ ** 0.25 not in gf # CZPowGate not in gate_types_to_check
>>> assert cirq.SQRT_ISWAP not in gf # ISwapPowGate not in gate_types_to_check

gates_to_accept List of gate types or instances to be accepted. All elements should be either types from POSSIBLE_FSIM_GATES or non-parameterized instances of those types.
gate_types_to_check List of POSSIBLE_FSIM_GATES types whose instances should be considered when trying to match against gates present in gates_to_accept. Defaults to all POSSIBLE_FSIM_GATES if left unspecified.
allow_symbols If True, both the gate conversion logic and containment predicate allow parameterized gate instances and return a converted gate / accept input gate if there exists any value of the unknown parameters which can result in a valid outcome.
atol Absolute tolerance for difference floating point comparisons.

ValueError If any gate in gates_to_accept is not a non-parameterized instance of / or a gate type from POSSIBLE_FSIM_GATES.
ValueError If any gate type in gate_types_to_check is not one of POSSIBLE_FSIM_GATES.

description

gate

name

Methods

convert

View source

Converts, if possible, the given gate to an equivalent instance of target_gate_type.

This method can be used for converting instances of POSSIBLE_FSIM_GATES to other equivalent types from the same group. For example, you can convert a sqrt iswap gate to an equivalent fsim gate by calling:

gf = cirq_google.FSimGateFamily()
assert gf.convert(cirq.SQRT_ISWAP, cirq.FSimGate) == cirq.FSimGate(-np.pi/4, 0)

The method can also be used for converting parameterized gate instances, by setting allow_symbols=True in the gate family constructor. Note that, conversion of paramaterized gate instances tries to be lenient and assumes that the correct parameters would eventually be filled during parameter resolution. This can also result in dropping extra parameters during type conversion, assuming the dropped parameters would be supplied the correct values. For example:

gf = cirq_google.FSimGateFamily(allow_symbols = True)
theta, phi = sympy.Symbol("theta"), sympy.Symbol("phi")
assert gf.convert(cirq.FSimGate(-np.pi/4, phi), cirq.ISwapPowGate) == cirq.SQRT_ISWAP
assert gf.convert(cirq.FSimGate(theta, np.pi/4), cirq.ISwapPowGate) is None

Args
gate cirq.Gate instance to convert.
target_gate_type One of POSSIBLE_FSIM_GATES types to which the given gate should be converted to.

Returns
The converted gate instances if the converion is possible, else None.

Raises
ValueError If target_gate_type is not one of POSSIBLE_FSIM_GATES.

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