threshold-filter[t] ket if x < t, return 0, else return x combined with drop, eg: drop threshold-filter[t] sp filter the given superposition to only those with coefficients >= t.
threshold-filter[2] (3|a> + 2.2|b> - 3 |c> + |d>) 3|a> + 2.200000|b> + 0|c> + 0|d> drop threshold-filter[2] (3|a> + 2.2|b> - 3 |c> + |d>) 3|a> + 2.200000|b>