1/ One of the most intriguing scientific challenges of the century is quantum computing. Nobody knows where it's going to go, and when.

2/ The scale of the difficulty is mind-boggling. It is exponentially more difficult than anything ever built in history, because we need to control quantum coherence to an unprecedentedly precise level.

3/ It is unclear that this can be done since not everything allowed by physics can actually be built.

There are three main types of outcomes:

4/ (1) Humanity one day builds a universal, fault-tolerant quantum computer. Maybe in ten years, or a hundred, or a thousand. We become masters of the universe -- we can simulate the universe according to its own rules, quantum physics, opening up previously inaccessible vistas.

5/ This leads to fundamental insights into the nature of space-time, quantum gravity, quantum field theory, advanced materials, and complex molecules, potentially playing a major role in civilization-changing technological advancements. It is an intoxicating thought.

6/ (2) We fail for a fundamental, unanticipated reason. Perhaps there is a fundamental reason that the level of control we are envisioning is just not possible, but we haven't understood why.

7/ Or the idea becomes obsolete. Maybe we learn that physically accessible measurements of quantum systems can be classically simulated efficiently -- perhaps the abstraction of an exponentially large Hilbert space somehow carries more baggage than necessary.

8/ Or (3) The problem turns out to just be too practically difficult. Like building a ladder to the moon, or a rocket ship traveling at 99% the speed of light.

9/ But the journey leads to new classical algorithms, better electronics, better sensors, and deeper insights into the states of matter and quantum mechanics itself. This has already occurred and is expected to continue to occur for the forseeable future.

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