Nature today published a (paywalled) article that mentions 'Self-accelerating Dirac wavepackets'. They claim that they behave in a similar fashion as the diffractive tricks of polarized beams that have light twist in a direction, but in this case with charged particles (A previous article by some of the authors on the same subject)
Now, on the media article (unfortunately I don't have access to the original paper, although I might end up buying a copy in a few days if I don't find someone to borrow a copy) they say that this happens due to 'uncertainty principle' and that the 'acceleration is compensated by larger position uncertainty in the opposite direction'.
I don't understand very well what that means, but I suspect what it means is that it cannot be used to accelerate a spaceship
What is your interpretation of the claims in the article? is this just useless for space propulsion? If as they also claim in the media article, the acceleration is indistinguishable from acceleration due to EM fields, I don't see why it wouldn't, but it wouldn't be the first time that quantum physics troll our expectations
Edit: It seems that the question boils down to what counter-force is exerted by the beam on the holographic mask grating used to generate the wavepacket, and how such counter-force would compare to a similar electron beam without any grating