If you have the capability to use DisplayPort or HDMI 2.0 (probably not) That's what you should be using.
Other than that you would need dual-hdmi support on your monitor (Multi-stream transport) and a dual-hdmi hardware (I don't think two cables cut it it might though), and it will not be true 4k either, it basically splits the image in half and renders them separately.
Aside from all of that. You need quite a bit of GPU power, depending on what you are trying to do.