  Friction is usually a very complicated process. It appears in its most
elementary form when two flat surfaces separated by vacuum gap are sliding
relative to each other at zero Kelvin and the friction is generated by the
relative movement of quantum fluctuations. For several decades physicists have
been intrigued by the idea of quantum friction. It has recently been shown that
two non-contacting bodies moving relative to each other experience a friction
due to quantum fluctuations inside the bodies \cite{VolokitinRMP2007}. However
until recent time there was no experimental evidence for or against this
effect, because the predicted friction forces are very small, and precise
measurements of quantum forces are incredibly difficult with present
technology. The existence of quantum friction is still debated even among
theoreticians \cite{Philbin2009,Pendry2010,VolokitinNJP2011}. However,
situation drastically changed with the creation of new material - graphene. We
recently proposed \cite{VolokitinPRL2011} that quantum friction can be observed
in experiments studying electrical transport phenomena in nonsuspended graphene
on amorphous SiO$_2$ substrate.
