Just need a tiny, stable black hole and some way of containing it. And then some way of scaling up the Casimir effect away from nanoscale electron microscopy.

Maybe you could create a collider scale facility and warp particles? From what I can understand, there's nothing wrong in principle, it's just that the conditions are currently absurdly beyond our reach.

There’s lots of things wrong with the naivest formulation, and plenty still wrong with the most sophisticated constructions: for example, you cannot steer your ship, as that requires violating casualty locally, and also you’d blast your destination with a shower of infinitely blue-shifted radiation.