Quantum Control Optimization Methods

Quantum computers being fabricated today, often referred to as noisy intermediate-scale quantum (NISQ) devices, have seen an increase in the number of qubits employed and an associated improvement in capabilities. Since the qubits are rapidly randomized by noise from the environment and thus lose coherence, NISQ devices are inherently susceptible to generating errors during computation. These devices operate under open-loop control without the benefit of error correction that is critical for their reliable operation. To meet this challenge, it is imperative to employ the best control design resources to assure that gate operations are performed at the highest fidelity while simultaneously being robust to inevitable uncertainties in device fabrication as well as noise from various sources. To this end, we are developing an integrated software product for control, characterization, calibration and optimization of quantum computers to address the above-mentioned fragility. The proposed STTR program will draw from the vast library of quantum control algorithms and software for control optimization and characterization developed at Princeton University and SC Solutions, Inc. (SC) in order to create an integrated set of software tools to meet the dual objectives of (a) computational design of reliable control and calibration for NISQ devices, and (b) guiding their fabrication and implementation. In Phase I, the SC-Princeton team has established the feasibility of developing a fully functional software framework which would allow the quantum researcher to perform software-guided control, calibration, optimization, and characterization in simulation and on quantum hardware. Through extensive interviews with potential customers from industry and university research laboratories, the team identified their needs to guide our software requirements. We have designed the software framework to be modular in order to enhance flexibility and increase the utility of the tools. Several representative algorithms for robust control optimization, calibration, and characterization have demonstrated the use of some common protocols defining only a few of the possible pathways to achieve the performance goals. The aim of the Phase II effort is to develop the software product prototype which can be interfaced with various NISQ systems. This software will accelerate the achievement of optimal performance while drawing upon the best features of the computational control design and experimental implementation in a real-time iterative fashion.The software toolset will consider the particular characteristics of each device, including the presence of often unknown error sources. The commercial product resulting from the Phase II effort will integrate the control, optimization, calibration, and characterization software tools into modules that will seamlessly interconnect and have a user-friendly interface. The software may be used for both off-line simulations and in experimental applications in a synergistic fashion. It will relieve quantum hardware developers from the burden of designing and implementing their own in-house quantum control and optimization software. Thus, operating in this fashion should accelerate the development of practical quantum computing.