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Things get strange when you shoot a single photon through the double slit. It deflects when passing through the slit, and when a string of distinct photons are sent, they accumulate in places where you’d expect in an interference pattern, but there is only one photon, and only one of two slits it could have passed through; yet it behaves as if it is interfering with itself. Here's my summary of a recent history of quantum physics: Anil Ananthaswamy’s Through Two Doors at Once. It uses the classic two-slit interference experiment as the common thread across generations of theories that try to explain its peculiar properties. Richard Feynman calls it the “one experiment which has been designed to contain all of the mystery of quantum mechanics.” With more complicated setups involving beam splitters, the photon will behave as a wave, as expected with multi-photon interference patterns, but if observed in its trajectory, it will act as a particle as one would expect, with nothing to interfere with its path. With more complex setups and long light paths, this bifurcation of behavior (wave or particle) can even be made to occur after the fact, warping our sense of time and causality. And it not just photons. Similar results have been achieved with neon atoms, C60 Buckyballs, and even a custom molecule of 810 atoms. The notion of superposition, required to explain this quantum interference, “is the most unsettling story perhaps to have emerged from any of the physical sciences since the seventeenth century.” Prof. David Albert, p.80. And then it gets really strange, when you consider the entanglement of photons that can collapse simultaneously when one is observed, even at a great distance away. This nonlocal behavior is a subject of much debate, including Einstein’s objections to quantum physics. Einstein’s most cited paper is not on relativity, it is his 1935 paper identifying the property of entanglement, which he called “spooky action at a distance.” The critical role that an observer plays in the experimental results (specifically, the collapse of the wavefunction in the Copenhagen interpretation) is a bit unsettling and anti-realist and reflective of the philosophical correctness of the day — with literary modernism questioning the ambiguities inherent to any one perspective of the world. In quantum physics and literary modernism, “there is no true world, since everything is but a perspectival appearance whose origin lies in us.” Prof. Albert p.183. The theory that I favor is the one that modifies neither philosophy nor physics and explains the two-slit experiment without resorting to an observer or the particle-wave duality; it solves determinism and non-locality, but… it is a psychological bender — the many interacting worlds interpretation. Each discrete photon is interfering with its sister particle in a parallel universe, and each quantum transition event spawns a copy of each universe, one for each path the particle could take. “The idea that 10^100 slightly imperfect copies of oneself all constantly splitting into further copies is not easy to reconcile with common sense. Here is schizophrenia with a vengeance.” Prof. DeWitt p.227. Thanks @anilananth for the good read. And this brings us to the Universe Splitter app on my iPhone. Each time I use it to make a decision, it directs a single photon through a beam splitter in Geneva, Switzerland, and there is subsequently one universe where the photon goes left and one where it goes straight. We happen to be in the one that observes one of those outcomes. When I read Feynman’s QED (Quantum Electrodynamics), I was struck by the peculiar squiggles that helped him visualize the path integral formulation of quantum mechanics. “The insight that Feynman had was to realize that what’s interfering are two different states of the universe. And those two states may only differ by where a single particle is.” Prof. Aephraim Steinberg, p.232. It was David Deutsch’s exploration of the two-slit experiment with single photons that guided him to parallel universes and the intuition behind quantum computers and their capacity to out-compute anything we could build that leveraged just one universe! And that brings us to the Entanglion game, published by IBM Research. I have yet to play that, in this universe at least, but hope to soon.

@lyn_beatz

I will talk about this on @wholemars’s Subscriber-only space on Sunday. Truth is my eight year-old Tesla was smoother than the Mercedes running NVIDIA software. But seeing how the @NVIDIA AI decomposes the road into all its parts shows me how it will handle all the weird stuff that happens on the road. And we’ll quickly get smoother. Tesla's advantage is the fleet. On Omar's Space on Sunday, I'm going to explain why the fleet is going to bring major advantages to Tesla. Until a car company or a group of car companies can get enough vehicles on the road with an NVIDIA computer, they're not going to be able to compete on experience in the car.

Just had a ride in the NVIDIA autonomous vehicle. I could argue that the Tesla is slightly smoother, but that is missing the point. The point I learned this week by hanging out with a bunch of different companies building autonomous vehicles is that AI at a variety of different companies is evolving so quickly that within 18 months you will see a bunch of different ones shipping and moving from level two (gotta pay attention) to level four (no human needed). Now the narrative will switch to one of scale. Uber went from an idea in a Paris snow storm to an international company driving people who live in slums in South Africa in four years. My expectation is that AVs will reach the slum in less time. Will it be a USA based company like Tesla? Or a Chinese company that reaches the slum (hence meaning it will reach at least 25% of humans on earth in between) first? We now will switch to one of convincing people AVs are a better way to get around than having humans drive. Regulation. Liability. Butts in seats. Experience. Price. And to all the engineers who worked in these things for 20 years: thank you. Your efforts will save millions of lives so my kids won’t have to go to more funerals when they are my age. Seven years ago @IrenaCronin and I wrote it is coming in our book. It took a while but it is finally here. Now the hard work of convincing every naysayer and hater is here.