College of Computing - Distinguished Seminar by Prof. Xiaoming SUN: Some Mathematical Problems in Quantum Circuit Synthesis and Optimization

29 January 2026 (Thursday)

The College of Computing (CC) was honoured to host a Distinguished Seminar on 29 January 2026, featuring Prof. Xiaoming SUN, Professor at the Institute of Computing Technology, Chinese Academy of Sciences (CAS) and a renowned expert in quantum computing research. Titled “Some Mathematical Problems in Quantum Circuit Synthesis and Optimization,” the seminar drew a large audience of CityUHK faculty members, students, and alumni eager to explore the mathematical foundations underpinning quantum circuit synthesis and optimization.

In the seminar, Prof. Sun introduced quantum circuits as the fundamental mathematical model and implementation framework for quantum algorithms, drawing parallels with logic circuits in classical computing. He explained that quantum circuits rely on reversible computing, where operations can be reversed without losing information – a property that is essential to quantum physics and important for improving energy efficiency. Using intuitive examples, he showed how complex quantum operations are constructed from simple reversible logic gates, such as the CNOT gate and the well‑known Toffoli gate, which together enable powerful quantum computations.

The seminar also highlighted how designing efficient quantum circuits for quantum algorithms presents new challenges, including reducing circuit size and execution time while carefully managing additional “helper” qubits, known as ancilla bits. Prof. Sun illustrated how these practical questions are closely linked to classic problems in mathematics and graph theory, using familiar analogies such as solving a Rubik’s Cube efficiently. He concluded by discussing recent advances and open research questions, including whether complex quantum operations can be performed faster without relying on extra qubits – an issue that remains at the forefront of quantum computing research.

The seminar featured active engagement from attendees, with particularly lively discussions during the Q&A session.

The seminar highlighted the College of Computing’s ongoing commitment to fostering academic excellence and international engagement. By hosting distinguished scholars such as Prof. Sun, the College provides valuable opportunities for its community to engage with cutting‑edge research and emerging technologies, strengthening CityUHK’s role in advancing innovation in computing.