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Decomposes a twoqubit operation into ZPow/XPow/YPow/sqrtiSWAP gates.
cirq.optimizers.two_qubit_matrix_to_sqrt_iswap_operations(
q0: "cirq.Qid",
q1: "cirq.Qid",
mat: np.ndarray,
*,
required_sqrt_iswap_count: Optional[int] = None,
use_sqrt_iswap_inv: bool = False,
atol: float = 1e08,
check_preconditions: bool = True
) > Sequence['cirq.Operation']
This method uses the KAK decomposition of the matrix to determine how many sqrtiSWAP gates are needed and which singlequbit gates to use in between each sqrtiSWAP.
All operations can be synthesized with exactly three sqrtiSWAP gates and
about 79% of operations (randomly chosen under the Haar measure) can also be
synthesized with two sqrtiSWAP gates. Only special cases locally
equivalent to identity or sqrtiSWAP can be synthesized with zero or one
sqrtiSWAP gates respectively. Unless required_sqrt_iswap_count
is
specified, the fewest possible number of sqrtiSWAP will be used.
Args  

q0

The first qubit being operated on. 
q1

The other qubit being operated on. 
mat

Defines the operation to apply to the pair of qubits. 
required_sqrt_iswap_count

When specified, exactly this many sqrtiSWAP
gates will be used even if fewer is possible (maximum 3). Raises
ValueError if impossible.

use_sqrt_iswap_inv

If True, returns a decomposition using
SQRT_ISWAP_INV gates instead of SQRT_ISWAP . This
decomposition is identical except for the addition of singlequbit
Z gates.

atol

A limit on the amount of absolute error introduced by the construction. 
check_preconditions

If set, verifies that the input corresponds to a 4x4 unitary before decomposing. 
Returns  

A list of operations implementing the matrix including at most three
SQRT_ISWAP (sqrtiSWAP) gates and ZPow, XPow, and YPow singlequbit
gates.

Raises  

ValueError

If required_sqrt_iswap_count is specified, the minimum number of
sqrtiSWAP gates needed to decompose the given matrix is greater
than required_sqrt_iswap_count .

References:
Towards ultrahigh fidelity quantum operations: SQiSW gate as a native twoqubit gate https://arxiv.org/abs/2105.06074