The Boolean noise operator averages a function over random coordinate reversals on . For
, let
have the discrete
uniform distribution on this set, and put
, where the signs
are independent
of
and one another, with
. The linear
operator is
where the right side is a conditional expectation (O'Donnell 2021, p. 55). Thus ,
, and
. On a Boolean
Fourier expansion, it acts diagonally,
Its crossover probability as a binary symmetric channel is .