We firstly revisit the energy loss mechanism known as quantum vacuum friction ( QVF ) , clarifying some of its subtleties .
Then we investigate the observables that could easily differentiate QVF from the classical magnetic dipole radiation for pulsars with braking indices ( n ) measured accurately .
We show this is specially the case for the time evolution of a pulsar ’ s magnetic dipole direction ( \dot { \phi } ) and surface magnetic field ( \dot { B } _ { 0 } ) .
As it is well known in the context of the classic magnetic dipole radiation , n < 3 would only be possible for positive ( \dot { B } _ { 0 } / B _ { 0 } + \dot { \phi } / \tan \phi ) , which , for instance , leads to \dot { B } _ { 0 } > 0 ( \dot { \phi } > 0 ) when \phi ( B _ { 0 } ) is constant .
On the other hand , we show that QVF can result in very contrasting predictions with respect to the above ones .
Finally , even in the case \dot { B } _ { 0 } in both aforesaid models for a pulsar has the same sign , for a given \phi , we show that they give rise to different associated timescales , which could be another way to falsify QVF .