Superconductors are kind of bizarre even in their ‘normal’ state. Normally all materials have at least a little bit of resistance to electrical current: pass a signal through a wire and at some point it will lose all of its energy. Over small distances of hundreds or even thousands of kilometers the loss might be negligable, but it is still there.
But if you cool certain materials to very cold (near absolute zero) temperatures, these materials enter a state where electrical resistance is non-existent. A current in such a material would go on forever without any loss in strength, a situation that leads to all sorts of unusual circumstances. Superconductors allow for extremely powerful magnets to be created that can be used for things like magnetic levitation trains or diagnostic imaging. These things exist and work today even with the difficulties involved in creating and maintaining the super-cold conditions that superconductors currently require.
But what if you could run superconductors outside of extremely cold conditions? The excess heat generated by resistive loss in most computers could be effectively eliminated, meaning clock rates could be increased significantly without components failing. Things like electric cars could be several times more efficient, MRI machines could be miniaturized, and entirely novel use cases for superconductivity in the home could be made practical. These are examples of the dream of room temperature superconductivity, a phrase that requires a bit of unpacking. A good article on Gizmodo discusses the current state of room temperature superconductivity and asks the question: when will it exist for real?
My Summary: Not for a while yet
There are a lot of disagreements about what constitutes “success” in the path towards practical “room temperature” superconductivity. Does the temperature have to be warmer than -100 degrees? Does the material need to have all the behaviours of superconductivity? Does the solution need to be practical in a home? There have been incremental steps towards success if you have broad definitions of these factors.
But if you think of superconductivity as being the behaviour seen in metals at or near absolute zero today, but at temperatures you’d find in a normal house, then progress has been slow indeed. There have been some breakthroughs around high-pressure superconductors using materials in the hydride family, but the pressure these materials require is almost as hard to maintain as low temperatures. Certainly hydride based high-pressure superconductors are impractical for use in a home based on what we know today.
The best guesses today for a timeline are that we are about twenty years away from having something a normal person would consider a practical room temperature superconductor- assuming such a thing is even possible. We are talking about something you could have in your laptop PC or at least in your electric car without an extraordinary amount of supporting equipment. This timespan sounds distressingly like the timeline for nuclear fusion: it, too, is always twenty years away. But thus far at least room temperature superconductivity hasn’t required the massive investment that fusion requires in order to make progress- that is good news.