  Expansion and amplification of weak randomness plays a crucial role in many
security protocols. Using quantum devices, such procedure is possible even
without trusting the devices used, by utilizing correlations between outcomes
of parts of the devices. We show here how to extract random bits with an
arbitrarily low bias from a single arbitrarily weak min-entropy source in a
device independent setting. To do this we use Mermin devices that exhibit
super-classical correlations. Number of devices used scales polynomially in the
length of the random sequence $n$. Our protocol is robust, it can tolerate
devices that malfunction with a probability dropping polynomially in $n$ at the
cost of a minor increase of the number of devices used.
