Optically Controlled Spin Gate Using GaN Quantum Dots

Two laterally positioned quantum dot single-photonemitters in different semiconductor heterostructures were analyzed. Acontrolled phase gate between two quantum dot spins was shown basedon the Coulomb interaction between the two quantum dot trions. Theinteraction shifts the bitrion energy manifold, enabling a pi-phase shift tobe acquired depending on the state of the control qubit. The gatefidelity increases with an increasing bitrion coupling which in turndepends on the spacing between the quantum dots. In practicalapplications, this spacing needs to be sufficiently large to allow the two-quantum-dot system to be fabricated. An enhanced bitrion coupling wasshown in In(Ga)N quantum dots both in a bulk GaN matrix and in a dot-in-wire geometry, compared to that in In(Ga)As dots. Theenhanced bitrion coupling in In(Ga)N dots increases the edge-to-edge interdot spacing needed to achieve the same gateperformance, allowing a deterministic spin-spin gate to be designed based on site-controlled dot-in-wire In(Ga)N quantum dotsthat can be readily fabricated with an interdot spacing of 10 nm using state-of-the-art lithography.