Transition metal impurities in Silicon: Computational search for a semiconductor qubit

TL;DR

This study computationally investigates transition metal impurities in silicon to identify potential optically active spin qubits, aiming to enhance scalability and operating temperature for quantum computing and communication applications.

Contribution

It provides the first comprehensive theoretical analysis of the entire 3d transition metal series in silicon for qubit potential using advanced computational methods.

Findings

Identified seven TM impurities with optically allowed triplet-triplet transitions within the silicon band gap.

Demonstrated potential for higher operating temperatures in silicon-based qubits.

Suggested applications in quantum sensing and mid-infrared communications.

Abstract

Semiconductors offer a promising platform for physical implementation of qubits, but their broad adoption is presently hindered by limited scalability and/or very low operating temperatures. Learning from the nitrogen-vacancy centers in diamond, our goal is to find equivalent optically active point defect centers in crystalline silicon, which could be advantageous for their scalability and integration with classical devices. Transition metal (TM) impurities in silicon are common paramagnetic deep defects, but a comprehensive theoretical study of the whole 3$d$ series that considers generalized Koopmans' condition is missing. We apply the HSE06(+U) method to examine their potential as optically active spin qubits and identify seven TM impurities that have optically allowed triplet-triplet transitions within the silicon band gap. These results provide the first step toward silicon-based qubits with higher operating temperatures for quantum sensing. Additionally, these point defects could lead to spin-photon interfaces in silicon-based qubits and devices for mid-infrared free-space communications.