Machine learning techniques for state recognition and auto-tuning in quantum dots

Recent progress in building large-scale quantum devices for exploring quantum computing and simulation has relied upon effective tools for achieving and maintaining good experimental parameters, i.e., tuning up devices. In many cases, including quantum dot-based architectures, the parameter space grows substantially with the number of qubits, and may become a limit to scalability. Fortunately, machine learning techniques for pattern recognition and image classification, using so-called deep neural networks, have shown surprising successes for computer-aided understanding of complex systems. We propose a new paradigm for fully automated experimental initialization through a closed-loop system relying on machine learning and optimization techniques. We use deep convolutional neural networks to characterize states and charge configurations of semiconductor quantum dot arrays when only measurements of a current−voltage characteristic of transport are available. For simplicity, we model a semiconductor nanowire connected to leads and capacitively coupled to depletion gates using the Thomas−Fermi approximation and Coulomb blockade physics. We then generate labeled training data for the neural networks, and find at least 90 % accuracy for charge and state identification for single and double dots. Using these characterization networks, we can then optimize the parameter space to achieve a desired configuration of the array, a technique we call “auto-tuning”. Finally, we show how such techniques can be implemented in an experimental setting by applying our approach to an experimental dataset, and outline further problems in this domain, from using charge sensing data to extensions to full one- and two-dimensional arrays, that can be tackled with machine learning. Machine learning: neural networks can learn to control quantum dots A machine learning algorithm connected to a set of quantum dots can automatically set them into the desired state. A group led by Jake Taylor at the National Institute of Standards and Technology with collaborators from the University of Maryland and India developed an approach based on convolutional neural networks which is able to “navigate” the huge space of parameters that characterize a complex, quantum system with neither human guidance nor reliance on a detailed description of the device. Instead they simulated thousands of hypothetical experiments and used the generated data to “train” the machine, which learned both to infer the