Here's a blog post that corresponds with what IBM presented at the 2019 March Meeting.
In this post, they claim they've measured qubit T1 relaxation times above 500 microseconds, and claim that they've seen evidence of genuinely entangled 18-qubit GHZ states.
This is far beyond anything that I've seen in published literature. The best results as far as I can find are 12 genuinely entangled qubits (up from 10) from the Pan group in China (1), and ~160 microsecond T1 times (2), also from IBM, but using a 3D cavity transmon qubit.
Assuming the claims are credible, what sort of advancements in fabrication (for the long coherence times) and microwave technology (for large entangled states) could allow such fast progress?