Universal Quantum Circuitry: High-Fidelity Deutsch Gate and Toffoli Gate Protocols Using GaAs/InAs Quantum Dots

We propose to incorporate two GaAs/InAs quantum dots in a larger circuit comprised of linear optical elements to create a spin-spin-photon polarization three-qubit Deutsch gate D(θ), where the parameter θ is tuned by rotating half-wave plates. Since the Deutsch gate is a universal quantum logic gate, a combination of Deutsch gates can complete any quantum computing task, a necessary condition for full-fledged quantum computing. Although Shi proposed to build a Deutsch gate using Rydberg blockade of neutral atoms [X-F Shi, Phys. Rev. Applied 9, 051001], no Deutsch gate has been experimentally realized so far. Our proposal offers another route toward a Deutsch gate realization using GaAs/InAs quantum dots. We display fidelity plots of our Deutsch gate protocol under realistic conditions for the GaAs/InAs quantum dots reporting fidelity values as high as 0.975. A single Deutsch gate can implement the much used Toffoli gate by operating at the appropriate angle, namely θ = π/2. We also identify a sub-circuit of our Deutsch gate circuit that yields a Toffoli gate protocol. We compare both Toffoli gate implementations—including their fidelity values—and highlight the advantages of the Deutsch gate protocol containing a sub-circuit Toffoli gate protocol.