Quantum Computing

Interpretations of quantum mechanics are boring. Boring! Maybe the universe has a strict partition between quantum and non-quantum. Maybe there are a bunch of parallel universes with limited crosstalk. Or maybe it’s whatever the Bohmian mechanics people are talking about. Shut up and calculate, I think. I don’t say this out of some disdain for idle philosophizing or to put on airs of a salt-of-the-earth laborer in the equation mines. It’s just there are so, so many interesting things you can learn about in quantum theory without ever going near the interpretation question. Yet it’s many peoples’ first & last stop. Rise above!

Quantum Computers: Not Just for Breaking RSA

There’s no denying it, Shor’s algorithm was a blockbuster result. The thought of an exotic new computer breaking all widely-used public-key crypto plays well with the public imagination, and so you’d be forgiven for believing quantum computing is ultimately a sort of billions-dollar make-work project for software engineers: forcing our profession to relive a Y2K-like mass upgrade of old systems to new, quantum-safe encryption algorithms. Great for consultants, bad for people who want resources invested toward actual social good.

Measurement and signaling in the nonlocal world

Popular understanding of quantum mechanics usually focuses on three learning objectives:

1. At small scales, particle properties (position, momentum, spin, etc.) are in superposition - they don’t have a definite value, but instead are “smeared” across multiple possible values.
2. Measuring a superposed particle property makes it collapse probabilistically to a specific value. We don’t simply discover the property’s pre-existing value; rather the property is forced to take on a definite value by the act of measurement.
3. Particles can be entangled, which means operations on one affect the other instantaneously across arbitrarily-large distances (known as nonlocality); however, this has restrictions and cannot be used for faster-than-light (FTL) communication.