dq.cosm

cosm(x: QArrayLike) -> QArray

Returns the cosine of a qarray.

Parameters

• x (qarray-like of shape (..., n, n)) –

  Square matrix.

Returns

(qarray of shape (..., n, n)) Cosine of x.

Note

This function uses jax.scipy.linalg.expm() to compute the cosine of a matrix \(A\): $$ \cos(A) = \frac{e^{iA} + e^{-iA}}{2} $$

Examples

>>> dq.cosm(jnp.pi * dq.sigmax())
QArray: shape=(2, 2), dims=(2,), dtype=complex64, layout=dense
[[-1.+0.j  0.+0.j]
 [ 0.+0.j -1.+0.j]]