Exploring semiconductor qubits: Simulation of a four quantum dot silicon device

Quantum computing represents a revolutionary computational paradigm with the potential to overcome the limitations of classical computers. Among the various approaches under investigation, semiconductor-based solutions stand out as promising candidates for qubit implementation. This work explores a four-quantum dot SiGe heterostructure. The above structure has been analyzed using the low-level finite element method-based simulator quantum technology computer-aided design (QTCAD) to derive essential physical parameters critical for implementing electron spin qubits. Even though QTCAD may not be as accurate as real experiments, it nonetheless provides important insights into the device behavior. The aim is to use these simulations to effectively analyze the device’s response to changes in structural parameters and determine whether it is feasible for real-world applications. As a result, changes to the structure can be made by simply modifying the simulation code, avoiding the need for repetitive and expensive lithographic processes. Notably, this is the first time a four-quantum-dot system has been analyzed using QTCAD. Specifically, the study involves solving the non-linear Poisson equation as well as single and multi particle Schrödinger equations. Additionally, a transport analysis is performed, yielding Coulomb peaks, Coulomb diamonds, and charge stability diagrams. Finally, an approximation of the tunneling coefficient and the exchange interaction energy between the different dot pairs is computed. The results provide a foundation for the design of advanced logic circuits able to execute multiple quantum logic gates. By leveraging the precise control over quantum dot configuration, it becomes possible to customize the interactions between quantum states for specific computational purposes. This approach enables the realization of complex architectures where individual quantum dots act as qubits or nodes in a quantum network. The ability to tune gate voltages and control inter-dot couplings allows for the implementation of complex quantum logic gates.