Week IV — supplemental reading

Entertainment and culture: Putting the brakes on quantum computation

In the past few years, a lot of hype surrounding quantum computers has been damped. Recent re-analyses of data suggests that the purported observation of Majorana fermions (hypothesized fermions that are their own antiparticle) in a supercooled semi-conductor turned out not to be the case. This is noteworthy, because Majorana fermions were thought to offer a way in which large, stable and scalable array of qubits necessary for viable quantum computing could be assembled. A recent pre-print has also shown that perhaps Google’s claim of having achieved `quantum supremacy’ — that is, of having an implementation of quantum computation that surpasses anything achievable by a classical computer, may in fact, have been premature.

Nevertheless, it is important to take everything in context. `Hype’ is not just an unavoidable part of our present form of capitalism, it may even be an essential component of fostering innovation, for the simple reason that it understates, if not obscures risk. This is absolutely crucial to encourage initial investment, be it in terms of resources or labor. If everyone was cynical of the possibilities from the outset, no one would ever take the chance to devote time and resources to an endeavor whose success is far from certain, and the field might never get off the ground (see this informative post by Steve Randy Waldan about the game theory of obfuscating risk in the context of finance). So even if the sheen of the initial hype has worn off, it has served its purpose in stimulating investment in quantum computation, which, if it ever becomes scalable commercial technology, could change the very nature of our civilization the same way computers themselves did at the start of the digital revolution. 

Why am I bringing any of this up? Well, in last weeks lecture, we learned about thermodynamic distance between two different macrostates of a system in thermal equilibrium. However, there is another notion of `distance’ of great importance in quantum systems — that of the time elapsed, specifically, the minimal time it takes to transition between distinct quantum states of a system. In order to determine how efficiently even an in principle ideal quantum computer could work, this aspect of quantum transitions needs to be understood, as it imposes a speed limit on quantum computation. This would serve as another important qualifier to some of the claims made of quantum computation. A recent paper has done just that, using the tools of information geometry. The relevant paper could even be a nice topic to cover in your project writeup (link also available on the coffee table)!

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