Is this enough close to the reference?
I use gradient texture for emission, bevel a bit the cube, and use object with emission under the big cube.
For have a quick render time, I use 256 samples, adaptative sampling to 0.01 and Super Image Denoiser.
To better match the reference, you need to ajust all the parameter of the sahder and to add a bit of glow in the hight lights in compositing.
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