# Site-selective quantum control in an isotopically enriched 28Si/SiGe quadruple quantum dot

## TL;DR

This paper demonstrates site-selective quantum control in an isotopically enriched 28Si/SiGe quadruple quantum dot, achieving high-fidelity single and two-qubit operations, including a fast CNOT gate, advancing silicon-based quantum computing.

## Contribution

It introduces coherent control in a quadruple quantum dot with tunable couplings and site-selective spin rotations, enabling scalable quantum gate operations in silicon.

## Key findings

- Tunable interdot tunnel couplings up to 20 GHz.
- Site-selective single spin rotations via electric dipole spin resonance.
- Resonant-CNOT gate executed in 270 ns.

## Abstract

Silicon spin qubits are a promising quantum computing platform offering long coherence times, small device sizes, and compatibility with industry-backed device fabrication techniques. In recent years, high fidelity single-qubit and two-qubit operations have been demonstrated in Si. Here, we demonstrate coherent spin control in a quadruple quantum dot fabricated using isotopically enriched 28Si. We tune the ground state charge configuration of the quadruple dot down to the single electron regime and demonstrate tunable interdot tunnel couplings as large as 20 GHz, which enables exchange-based two-qubit gate operations. Site-selective single spin rotations are achieved using electric dipole spin resonance in a magnetic field gradient. We execute a resonant-CNOT gate between two adjacent spins in 270 ns.