Quantum-cellular-automata quantum computing with endohedral fullerenes

TLDR

Each endohedrally doped fullerene hosts a quartet electron spin ground state, and neighboring electron spins interact via magnetic dipole coupling. The authors propose a universal quantum computing scheme using global addressing on an ABAB linear array of group‑V endohedrally doped fullerenes, aiming to satisfy the first four DiVincenzo criteria and enable qubit readout. The architecture encodes qubits in nuclear spins coupled to electron spins via hyperfine interaction, and NMR/ESR pulses implement cellular‑automaton gates, yielding a figure of merit for gate operations per decoherence time. The study finds that an all‑electron quantum cellular automaton is frustrated by electronic transition degeneracy, but encoding qubits on nuclear spins produces a figure of merit comparable to other proposals and meets the first four DiVincenzo criteria.

Abstract

We present a scheme to perform universal quantum computation using global addressing techniques as applied to a physical system of endohedrally doped fullerenes. The system consists of an $\mathcal{ABAB}$ linear array of group-V endohedrally doped fullerenes. Each molecule spin site consists of a nuclear spin coupled via a hyperfine interaction to an electron spin. The electron spin of each molecule is in a quartet ground state $S=3/2.$ Neighboring molecular electron spins are coupled via a magnetic dipole interaction. We find that an all-electron construction of a quantum cellular automaton is frustrated due to the degeneracy of the electronic transitions. However, we can construct a quantum-cellular-automata quantum computing architecture using these molecules by encoding the quantum information on the nuclear spins while using the electron spins as a local bus. We deduce the NMR and ESR pulses required to execute the basic cellular automaton operation and obtain a rough figure of merit for the number of gate operations per decoherence time. We find that this figure of merit compares well with other physical quantum computer proposals. We argue that the proposed architecture meets well the first four DiVincenzo criteria and we outline various routes toward meeting the fifth criterion: qubit readout.