> photon-based internet like network
If propagation delay is the concern (talking about high frequency) then electrons over copper do a better job than photons over fiber. (grain of salt, future dedicated photonic interconnect may have better performance).
> Our brain is much more powerful than current processor
Again, if we're talking about frequency (30GHz, 1THz) the brain is faster due to the way it's organized not because it operates at high frequencies.
> Even 1THz is possible with modern tech [...] super fast single-atom processors
Not in any meaningful way and we certainly aren't anywhere near "single-atom processors".
Perhaps your comment meant to say that sometime in the future we won't need high frequency because we'll change the way we design processors, not that we can build 1THz CPUs because our brain is more powerful then them.
It's possible to do a lot with "modern technologies", even cure cancer or solve world hunger etc., we just either haven't actually found a way to do some of those things, or at least not a feasible, useful way. This renders the statement a bit meaningless. We've had THz transistors for a decade now. There are dozens of reasons you don't see them in general purpose CPUs though.