Composing $p$-adic qubits: from representations of SO(3)$_p$ to entanglement and universal quantum logic gates
Ilaria Svampa, Sonia L'Innocente, Stefano Mancini, Andreas Winter
TL;DR
This work elevates $p$-adic quantum mechanics by formulating qubits as 2-dimensional irreducible representations of $SO(3)_p$ and building a full information-processing program around representations, Clebsch–Gordan analysis, entanglement, and quantum gates. It shows that all finite-dimensional reps of $SO(3)_p$ factor through finite quotients $G_{p^k}$, enabling a finite-group approach to qubits and their interactions. The Clebsch–Gordan problem for two $p$-adic qubits yields singlet and doublet (and, for $p=3$, triplet) structures, with entanglement properties tied to the corresponding subrepresentations; the paper provides explicit CG coefficients for small primes and a general framework. Most notably, at $p=3$ the authors construct a universal set of $3$-adically controlled quantum gates from 4D irreps of $G_3$, proven via Lie-algebraic methods and Givens-rotation decompositions, establishing computational universality in this $p$-adic setting and suggesting a path toward adelic formulations that unify real and $p$-adic quantum theories.
Abstract
In the context of $p$-adic quantum mechanics, we investigate composite systems of $p$-adic qubits and $p$-adically controlled quantum logic gates. We build on the notion of a single $p$-adic qubit as a two-dimensional irreducible representation of the compact $p$-adic special orthogonal group SO(3)$_p$. We show that the classification of these representations reduces to the finite case, as they all factorise through some finite quotient SO(3)$_p$ mod $p^k$. Then, we tackle the problem of $p$-adic qubit composition and entanglement, fundamental for a $p$-adic formulation of quantum information processing. We classify the representations of SO(3)$_p$ mod $p$, and analyse tensor products of two $p$-adic qubit representations lifted from SO(3)$_p$ mod $p$. We solve the Clebsch-Gordan problem for such systems, revealing that the coupled bases decompose into singlet and doublet states. We further study entanglement arising from those stable subsystems. For $p=3$, we construct a set of gates from $4$-dimensional irreducible representations of SO(3)$_p$ mod $p$ that we prove to be universal for quantum computation.
