Zoom registration: https://harvard.zoom.us/webinar/register/WN_q8rI_YJWS2GiLNyxVADNKA

Recent development in quantum information has led to breakthroughs in quantum technologies, which has brought us to a new Information Age. Noisy Intermediate-Scale Quantum (NISQ) computers with number of quantum bits (qubits) ranging from fifty to a few hundreds and the limited size of quantum circuits are expected to be available in near future. In particular, variational quantum algorithms (VQAs) based on the quantum-classical optimization loop are recently considered as a leading strategy for the realization of NISQ computers. However, there are still key open problems in the theoretical and practical aspects of VQAs. These include the rigorous analysis on the trainability of VQAs and their envisaged interdisciplinary applications. In this colloquium, I will introduce my past research and summarize my research plans regarding NISQ computers. First, I will discuss how the locality of the measurements and the circuit depth relate to the trainability of VQAs, and introduce their physical insights by considering the Hamiltonian-based VQAs. Then, I will introduce the VQAs for the preparation of the optimal quantum sensors for the single-parameter estimation. These research on quantum sensing and NISQ computers can open an exciting future research direction to realize precise multiple-parameter estimation by using near-term quantum computers, which can be applied in broader fields such as chemistry, material science and biology.