there's a bit of a compromise where we say it is the same neural network but but basically this one is the one we learn and then we always every now and then we transfer over the parameters to that one and in fact each step we transfer over the parameters and do an exponential moving average with the parameters of this momentum encoder from the step before so the momentum encoder parameters are a moving average of the parameters of the query encoder and that is so you get kind of get the best of both worlds you don't