“LIGO is this huge thing that thousands of people have been thinking about deeply for 40 years,” Aephraim Steinberg is an expert in quantum University of Toronto, Department of Optics “They’ve thought of everything they could have, and anything new [the AI] comes up with is a demonstration that it’s something thousands of people failed to do.”
AI, although it may not have led to any new physics discoveries yet, is a very powerful tool. It can also help researchers design experiments and find patterns that are not trivial in data. AI algorithms can, for instance, extract symmetry from data collected by the Large Hadron Collider located in Switzerland. These symmetries aren’t new—they were key to Einstein’s theories of relativity—but the AI’s finding serves as a proof of principle for what’s to come. AI was also used by scientists to create a formula that describes the dark matter clumping. “Humans can start learning from these solutions,” Adhikari says:
Separate but not Together
Classical physics, which describes the world we live in, is characterized by objects with well-defined characteristics that can be measured independently. For example, a billiard ball has its own position and velocity at any moment.
The quantum world is different. Quantum objects are described mathematically by the quantum state. One can use the quantum state to estimate the likelihood of finding the object at, say, a specific location.
It is also possible for two or more quantum objects to share one quantum state. Photons are the building blocks of light. Photons may be produced in pairs. “entangled,” Meaning that even though they may fly apart, the two photons still share one quantum state. Once one of the two photons is measured, the outcome seems to instantaneously determine the properties of the other—now distant—photon.
Over the years, scientists have assumed that quantum objects must start in the same location. In the 1990s however, a new theory was proposed. Anton Zeilinger. receive the Nobel Prize in Physics His studies on entanglement showed this was not always the case. The experiment he and his co-workers proposed began with two pairs of unrelated entangled photos. As well as photons A andB, researchers also entangled C andD. devised a clever experimental design made of crystals, beam splitters and detectors that would operate on photons B and C—one photon from each of the two entangled pairs. In a set of operations, photons C and B are detected and destroyed. However, as a result, particles A and Z, who had not interacted previously, also become entangled. Entanglement swapping is a key building block in quantum technology.
That was the state of affairs in 2021, when Krenn’s team started designing new experiments with the aid of software they dubbed PyTheus—Py for the programming language Python, and Theus for Theseus, after the Greek hero who killed the mythical Minotaur. The team used mathematical structures known as graphs to represent optical experiments. These graphs are made of nodes and connected by lines, called edges. Nodes and lines represented various aspects of an experimental setup, including beam splitters, photon paths, and whether or not there was interaction between two photons.
