QDarts: Quantum Dot Array Simulator Enhances Control Over Semiconductor-Based Spin Qubit Devices

QDarts, a Quantum Dot Array Transition Simulator, has been developed by researchers from Universiteit Leiden and the University of Copenhagen. The software simulates charge stability diagrams, focusing on sensor simulation of selected transitions. It is designed to process quantum information in semiconductor-based spin qubit devices, providing an efficient framework for simulating charge occupation.

QDarts extends the Constant Interaction Model and includes features such as variation of dot capacitances and effects of finite coherent tunnel coupling. The simulator is expected to be a valuable tool in understanding experimental data and testing control algorithms for quantum dot arrays.

What is QDarts and its Purpose?

QDarts, a Quantum Dot Array Transition Simulator, is a software designed to simulate realistic charge stability diagrams. These diagrams display regions of constant charge occupation in an arbitrary 2D cut through high dimensional voltage space, with a focus on a realistic sensor simulation of the selected transitions. The simulator was developed by a team of researchers from the Applied Quantum Algorithms at Universiteit Leiden, The Netherlands, and the Department of Computer Science at the University of Copenhagen, Denmark.

The purpose of the simulator is to process quantum information in semiconductor-based spin qubit devices, which requires detailed control over charge occupation in multiple electrically-defined quantum dots. The simulator represents a significant advancement in modelling realistic scenarios for state-of-the-art moderate-size devices. It provides an efficient framework for simulating the charge occupation of the device together with a tunable model of the sensor signal.

What are the Features of QDarts?

QDarts efficiently realizes and extends the commonly used Constant Interaction Model (CIM). It possesses a selection of commonly observed experimental features such as variation of dot capacitances as a function of charge occupation, effects of finite coherent tunnel coupling between the dots, and realistic modelling of the sensor dot signal that includes tunable noise parameters.

The model purposely does not include the spin degree of freedom, allowing for faster simulations and thus to scale this simulator to larger devices. This enables more advanced simulations of device behaviour such as tunnel couplings and sensor dots. However, when these advanced features are not needed, the modular nature of the simulator allows purely classical simulations of the ground states of the underlying capacitance model.

How is QDarts Beneficial?

The simulator is envisioned to be useful in understanding experimental data as well as for testing control algorithms developed for quantum dot arrays, especially for charge transition detection and state identification. The simulator has been validated by benchmarking it against a selection of state-of-the-art experiments.

The goal of the simulator is to be as close as possible to real device behaviour and thus setting up the simulation requires some of the tuning steps that are also found in real devices. For this reason, the simulator also provides tools to set up an initial tuning point, including sensor tuning and virtualisation of the gates, which translates applied voltages into arbitrary combinations of dots’ chemical potentials.

Demonstration of QDarts

To demonstrate the simulator’s efficiency and fidelity, a 100×100 2D scan of a quadruple dot device interacting with two noisy sensor dots was computed. The simulator was able to compute this on a laptop in under a minute. The outcome aimed to reproduce the result of a previous experiment, where a multi-electron transition was simulated. In this example, two interdot transitions intersect at a point representing the simultaneous occurrence of both transitions. This transition is a natural result from the simulator, obtained using a few-line prompt.

Conclusion

In conclusion, QDarts is a significant advancement in the field of quantum dot array simulations. It provides an efficient and realistic model for simulating charge stability diagrams, with a focus on sensor simulation of selected transitions. The simulator is expected to be a valuable tool in understanding experimental data and testing control algorithms for quantum dot arrays.