Software defined radio (SDR) is a relatively new technology that has impacted the world of radio technology in many ways. But beyond SDR, there are still some other very interesting radio technologies being worked on, such as "Atomic Radio" a.k.a "Quantum Radio".
Atomic radio is essentially an idea that makes use of how special "Rydberg" atoms can modulate a laser beam when radio waves pass through them. A photo diode is then used to optically detect the radio wave from the modulated laser. This way of receiving requires no traditional radio circuits like amplifiers, mixers, and of course no antenna, so in theory the radio signal could be received with significantly less noise and with the highest possible SNR.
If you're interested in learning more about Atomic Radio, Hackaday recently ran an excellent article where they describe the concept and science behind it in more depth. They also go into some recent studies where scientists showed that they were able to receive two signals at once, and mention how one paper describes an extremely wideband Atomic Radio that can receive from the C-Band to the Q-band (4 GHz to 50 GHz).