Skip to content

dq.vacuum_dm 

vacuum_dm(dim: int) -> QArray

Returns the density matrix of the vacuum state.

It is the Fock state with zero photon, defined by \(\ket{0}\bra{0} = \begin{pmatrix}1 & 0 & \cdots\\0 & 0 & \cdots\\\vdots & \vdots & \ddots \end{pmatrix}\).

Parameters:

  • dim –

    Hilbert space dimension of the mode.

Returns:

  • (qarray of shape (dim, dim)) –

    Density matrix \(\ket{0}\bra{0}\).

Examples:

>>> dq.vacuum_dm(4)
QArray: shape=(4, 4), dims=(4,), dtype=complex64, layout=dense
[[1.+0.j 0.+0.j 0.+0.j 0.+0.j]
 [0.+0.j 0.+0.j 0.+0.j 0.+0.j]
 [0.+0.j 0.+0.j 0.+0.j 0.+0.j]
 [0.+0.j 0.+0.j 0.+0.j 0.+0.j]]