The Nature paper that this press release talks about is [0], and even better, the same issue of Nature also published an accompanying "News and Views" explanation of the paper for non-experts [1] which I thought was clarifying:

> A report by Wang et al.5 ( page 277 of this issue) now demonstrates a very large superluminal effect for pulses of visible light, in which a pulse propagates in a specially prepared medium [...] not only faster than a pulse travelling in a vacuum, but so fast that the peak of the pulse exits the medium before it enters it! [...]

> their light pulses do not violate causality. [...] They use smooth, well-defined light pulses, so that the peak of the pulse at the output results from the forward rising edge of the input pulse, which occurs far earlier in time, making it consistent with causality. An abrupt feature in the light pulse would not be able to travel faster than c.

[0] https://www.nature.com/articles/35018520?proof=t [1] https://www.nature.com/articles/35018657?draft=journal&proof...