AI makes its first meaningful breakthrough in theoretical physics

One of the greatest challenges — and perhaps the most important challenge of all — for any theoretical physicist is to connect something you can predictively calculate to something you can go out and measure experimentally or observationally. This is the key not just to testing your current best understanding of reality, but to discovering any anomalies that could pave the way forward to the next revolution in our conception of the Universe. Most of the great revolutions in physics history have arisen where theory and observation/experiment have failed to match, including: Over the past few generations, quantum field theory is how we arrive at the most precise physical predictions ever made.

The act of testing those predictions against particle physics experiments has led to incredible discoveries, the spectacular confirmation of the Standard Model, and drives our great hopes for finally going beyond it. But calculating observables like cross-sections and scattering amplitudes to greater and greater precisions is computationally hard; physicists have been stuck for many years, unable to surpass the current limits. That’s why it’s so remarkable that an LLM-based AI has just done what humans hadn’t been able to do on their own: calculate an important theoretical result in quantum field theory to a greater loop-order than any human, even with the aid of computers, had ever done previously.

Here’s the story of what just happened, and why it matters. This diagram illustrates the inherent uncertainty relation between position and momentum. When one is known more accurately, the other is inherently less able to be known accurately.

Both position and momentum are better described by a probabilistic wavefunction than by a single value. Other pairs of conjugate variables, including energy and time, spin in two perpendicular directions, or angular position and angular momentum, also exhibit this same uncertainty relation. One of the most important ways of conceiving of our Universe is through the lens of quantum field theory.

In order to understand what this breakthrough is all about, we have to understand what’s so important (and different) about quantum field theory from all prior conceptions of reality. Our original view of physics was Newtonian: where reality is made up of particles with well-defined properties like mass, position, and velocity, and where those particles move through space with the passage of time. As a consequence of Einstein, we learned that space and time are linked, and that space itself is not flat, static, and unchanging, but rather can be curved and can evolve. (That notion of spacetime now serves as the backdrop in both classical and quantum physics.) The main insight of the quantum revolution was that what we think of as particles don’t necessarily have fixed properties, but rather things like “where they are,” “how fast they’re moving,” and even (if they’re unstable) “how much they weigh” follow a probability distribution instead.

Only when you make a measurement — via the interaction of that quantum with another one — to actually find out what a particular particle’s properties are is a particular value determined for one particular property. But if you repeat the experiment over and over again, even with identical initial conditions, you won’t get that same result over and over again; you’ll get a probability distribution for your results. The inherent width, or half the width of the peak in the above image when you’re halfway to the crest of the peak, is measured to be 2.5 GeV: an inherent uncertainty of about +/- 3% of the total mass.