Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Fricke Topological Qubits

Version 1 : Received: 7 October 2022 / Approved: 10 October 2022 / Online: 10 October 2022 (11:14:48 CEST)

A peer-reviewed article of this Preprint also exists.

Planat, M.; Chester, D.; Amaral, M.M.; Irwin, K. Fricke Topological Qubits. Quantum Rep. 2022, 4, 523-532. Planat, M.; Chester, D.; Amaral, M.M.; Irwin, K. Fricke Topological Qubits. Quantum Rep. 2022, 4, 523-532.


We recently proposed that topological quantum computing might be based on $SL(2,\mathbb{C})$ representations of the fundamental group $\pi_1(S^3\setminus K)$ for the complement of a link $K$ in the $3$-sphere. The restriction to links whose associated $SL(2,\mathbb{C})$ character variety $\mathcal{V}$ contains a Fricke surface $\kappa_d=xyz -x^2-y^2-z^2+d$ is desirable due to the connection of Fricke spaces to elementary topology. Taking $K$ as the Hopf link $L2a1$, one of the three arithmetic two-bridge links [the Whitehead link $5_1^2$, the Berge link $6_2^2$, the double-eight link $6_3^2$] or the link $7_3^2$, the $\mathcal{V}$ for those links contains the reducible component $\kappa_4$, the so-called Cayley cubic. In addition, the $\mathcal{V}$ for the later two links contains the irreducible component $\kappa_3$, or $\kappa_2$, respectively. Taking $\rho$ to be a representation with character $\kappa_d$ ($d<4$), with $|x|,|y|,|z| \le 2$, then $\rho(\pi_1)$ fixes a unique point in the hyperbolic space $\mathcal{H}_3$ and is conjugate to a $SU(2)$ representation (a qubit). Even though details on the physical implementation remain open, more generally, we show that topological quantum computing may be developed from the point of view of three-bridge links, the topology of the $4$-punctured sphere and Painlev\'e VI equation. The $0$-surgery on the $3$ circles of the Borromean rings L6a4 is taken as an example.


n/a; Topological quantum computing; $SL(2,\mathbb{C})$ character variety; knot theory


Computer Science and Mathematics, Geometry and Topology

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