# cirq.bit_flip

Construct a BitFlipChannel that flips a qubit state with probability p.

### Used in the notebooks

Used in the tutorials

If p is None, this returns a guaranteed flip in the form of an X operation.

This channel evolves a density matrix via

$\rho \rightarrow M_0 \rho M_0^\dagger + M_1 \rho M_1^\dagger$

With

\begin{aligned} M_0 =& \sqrt{p} \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix} \\ M_1 =& \sqrt{1-p} \begin{bmatrix} 0 & 1 \\ 1 & -0 \end{bmatrix} \end{aligned}

p the probability of a bit flip.

ValueError if p is not a valid probability.

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