Device Characterization and Error Mitigation

We focus on developing characterization and calibration experiments for quantum computing, including for noise, the main obstacle for quantum computers. We study the effect of noise on quantum devices and develop experiments and methods to characterize and mitigate noise. We also seek to enhance and invent new quantum dynamic tools in Qiskit, the open-source software development kit for quantum computers, for modelling and numerically simulating quantum hardware, analyzing cloud-based experiments on IBM Quantum devices, characterizing and estimating device parameters, and improving the control of device dynamics.

Quantum Circuit Synthesis and Optimization

Quantum circuits are the backbone programs in quantum computing. Because quantum devices are noisy due to the very nature of quantum computing, which requires creating fragile superposition states of qubits and interactions between them, the depth of quantum circuits is limited in practical applications. Given a quantum program, generating efficient quantum circuits is vital if we want to fully utilize the potential of the quantum computer. Our aim is to reduce the depth of certain quantum circuits to squeeze more useful operations within the circuit depth limits. The research involves using methods from group theory, computing science, and optimization. We perform original research as well as contribute new algorithms to Qiskit.

Quantum Circuit Simulation

A quantum computer can be simulated on a classical computer. Specifically, we can run quantum circuits using special programs called quantum circuit simulators, which store the statevector as an array of 2^n complex numbers, where n is the number of qubits, or by representing a circuit with the matrix product state (MPS), where every qubit is represented by a tensor, or 3D matrix of complex numbers, with a 1D vector between every two consecutive tensors. These methods allow us to study interesting properties of our quantum program, quantum device, and the effect of noise on both. Our team is developing advanced and efficient methods for quantum circuit simulation based on the MPS approach, including approximation methods.