# Copyright 2018 The Cirq Developers
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Operations native to iontrap systems."""

import numpy as np

from cirq import ops
from cirq._compat import deprecated


def ms(rads: float) -> ops.XXPowGate:
    """The Mølmer–Sørensen gate, a native two-qubit operation in ion traps.

    A rotation around the XX axis in the two-qubit bloch sphere.

    The gate implements the following unitary:

        exp(-i t XX) = [ cos(t)   0        0       -isin(t)]
                       [ 0        cos(t)  -isin(t)  0      ]
                       [ 0       -isin(t)  cos(t)   0      ]
                       [-isin(t)  0        0        cos(t) ]

    Args:
        rads: The rotation angle in radians.

    Returns:
        Mølmer–Sørensen gate rotating by the desired amount.
    """
    return ops.XXPowGate(exponent=rads*2/np.pi, global_shift=-0.5)


@deprecated(deadline='v0.8.0', fix='Use cirq.ms, instead.')
def MS(rads: float) -> ops.XXPowGate:
    return ms(rads)
