Review of The Quantum Thief

I don’t often encounter the phrase ‘quantum process tomography’ in a fiction book. Hannu Rajaniemi is a very particular author, and I recently enjoyed reading his Jean le Flambeur trilogy, beginning with The Quantum Thief, followed by The Fractal Prince, and finally The Causal Angel. There’s a sense in which my first paper is about quantum process tomography, so I felt compelled to write a few words. These books are the most impressive science fiction I’ve read, though perhaps that’s not so surprising given Rajaniemi’s background, which extends from a PhD in string theory to founding an mRNA startup. And they really do assume a lot of knowledge on the part of the reader.

The Sobornost are a collective of gogols, uploaded human minds in the vein of Robin Hanson’s ems, descended and copied primarily from a few Founders. Driven to religious fervour by Nikolai Fedorov’s Great Common Task, they seek to defeat death and resurrect the dead. Their primary opposition are the Zoku, posthumans whose minds are stored in jewels as quantum information and entangled with other Zoku minds in collectives that bind together their extrapolated volition, resembling and punning in a way on Eliezer Yudkowsky’s concept of coherent extrapolated volition. The no-cloning theorem prevents the copying of the quantum information, exposing the Zoku to the possibility of death—anathema to the Sobornost.

The titular quantum thief, Jean le Flambeur, begins the series in the Dilemma Prison, a Sobornost creation that aims to rehabilitate its inmates by forcing them to play out the classic prisoners’ dilemma. Or, rather, the classical prisoners’ dilemma. You see, this prison is a little ironic: contrast the religious hatred of the Sobornost for quantum mechanics and ‘quantum filth’ with the quantum prisoners’ dilemma, where players that share quantum entanglement can employ a quantum strategy, rendering the Nash equilibrium Pareto optimal. Indeed, the Zoku utilise quantum pseudo-telepathy to enable arcane forms of faster-than-light coordination throughout the series. In the realm of quantum information, there is no need for defection. Thus it is only natural that the All-Defector, which reminds me of worries about demons in the Solomonoff prior, emerges from the Sobornost’s classical Dilemma Prison.

Throughout my PhD, I’ve spent rather more time reading about the singularity than I have on the arXiv reading about quantum information theory. These novels reward knowledge of both, and so they feel to me like home. The reference I’m most amused to have caught was to the tech locks of Karl Schroeder’s Lady of Mazes, which I recently read owing to its influence on Hieronym’s To The Stars, my favourite (though ongoing) work of science fiction. I’m sure there are many more references I didn’t catch.

The series is fundamentally concerned with identity, death, and immortality. But on this front, I can’t compete with Gwern’s review of the trilogy, adored by Rajaniemi himself. So if I’ve piqued your interest, I recommend reading the books and then Gwern’s review. I think they’re worth the effort.