Quantum Coulomb Blockade in Orbital Resolved Phosphorus Triple-Donor Molecule

Abstract

Multi-donor architecture in silicon offers a promising direction towards scalable solid-state qubits and quantum technologies operating at practical conditions. However, the overlap of multiple donor wave-functions develops a complex internal electronic configuration with several discrete energy levels. Probing these discrete-correlated states is essential for understanding inter-donor coupling and exchange interactions towards their practical implementations in quantum-technologies. We have experimentally demonstrated quantum Coulomb blockade mediated systematic filling of several electrons into orbital-resolved molecular states within multi-phosphorous-donor molecules accompanied by a correlated decrement in charging energies for higher hybridized orbitals due to expanded Bohr radii and electron delocalization. Corresponding, first-principle density functional theory calculations offer microscopic insight into the orbital configurations, while the rate equation simulations of quantum Coulomb blockade faithfully reproduce the experimental stability diagrams. This comprehensive characterization advances and discusses the role of donor-molecules in silicon in scalable building blocks for quantum technologies operable at elevated temperatures.