Working Paper Article Version 1 This version is not peer-reviewed

# Quantum Computation and Measurements from an Exotic Space-time $R^4$

Version 1 : Received: 17 March 2020 / Approved: 18 March 2020 / Online: 18 March 2020 (16:45:55 CET)

How to cite: Planat, M.; Aschheim, R.; Amaral, M.; Irwin, K. Quantum Computation and Measurements from an Exotic Space-time $R^4$. Preprints 2020, 2020030287 Planat, M.; Aschheim, R.; Amaral, M.; Irwin, K. Quantum Computation and Measurements from an Exotic Space-time $R^4$. Preprints 2020, 2020030287

## Abstract

The authors previously found a model of universal quantum computation by making use of the coset structure of subgroups of a free group $G$ with relations. A valid subgroup $H$ of index $d$ in $G$ leads to a \lq magic' state $\left|\psi\right\rangle$ in $d$-dimensional Hilbert space that encodes a minimal informationally complete quantum measurement (or MIC), possibly carrying a finite \lq contextual' geometry. In the present work, we choose $G$ as the fundamental group $\pi_1(V)$ of an exotic $4$-manifold $V$, more precisely a \lq small exotic' (space-time) $R^4$ (that is homeomorphic and isometric, but not diffeomorphic to the Euclidean $\mathbb{R}^4$). Our selected example, due to to S. Akbulut and R.~E. Gompf, has two remarkable properties: (a) it shows the occurence of standard contextual geometries such as the Fano plane (at index $7$), Mermin's pentagram (at index $10$), the two-qubit commutation picture $GQ(2,2)$ (at index $15$) as well as the combinatorial Grassmannian Gr$(2,8)$ (at index $28$) , (b) it allows the interpretation of MICs measurements as arising from such exotic (space-time) $R^4$'s. Our new picture relating a topological quantum computing and exotic space-time is also intended to become an approach of \lq quantum gravity'.

## Subject Areas

Topological quantum computing; $4$-manifolds; Akbulut cork; exotic $R^4$; fundamental group; finite geometry; Cayley-Dickson algebras

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