Notice
Seminar
Group Lecture & Seminar
Author
admsquis
Date
2025-11-04
Views
115
Our group alumni,
- Prof. Hyukgun Kwon from Sejong University,
- Prof. Seokhyung Lee from Sungkyunkwan University,
and a visiting graduate student,
- Lucas English from University of Sydney,
will be giving a seminar in Seoul National University
- Date and time: November 4th(Tuesday) 2:00 p.m
- Venue: NextQuantum Center Meeting Room ( 56-1 Dong 2nd floor)
- Lecture information
1) Speaker: Prof. Lee Seok-hyung (Sungkyunkwan University)
Title: Efficient Post-Selection for General Quantum LDPC Codes
Abstract:
In quantum error correction, post-selection is a powerful technique to boost the effective fidelity of a computation by discarding low-confidence results. However, the representative logical gap method faces major obstacles: It can be computationally expensive (scaling exponentially with the number of logical qubits) and is limited to specific codes like the surface code that allow the MWPM decoder. In this talk, I will introduce a new approach to overcome these limitations. This approach leverages efficient heuristic decoding confidence metrics based on error cluster statistics from clustering-based decoders (such as BP+LSD). Importantly, our method works for a broad range of quantum low-density parity check (QLDPC) codes, not just surface codes. Moreover, it shows orders of magnitude reduction in logical error rates with only modest abort rates. Lastly, it can be naturally integrated with real-time decoding via the sliding-window framework, featuring early mid-circuit abort decisions. Our post-selection strategies are expected to be particularly useful for offline resource state generation processes (such as magic state preparation) with QLDPC codes.
2) Speaker: Prof. Kwon Hyuk-gun (Sejong University)
Title: How to achieve and preserve quantum advantage in quantum metrology
Abstract:
Quantum metrology investigates how quantum resources can enhance the estimation performance. Over the past years, numerous studies have shown that quantum coherence and entanglement can potentially achieve higher estimation precision compared to classical methods. These advantages have been explored in a wide range of applications, including gravitational wave detection, interferometry, magnetometry, atomic clocks, or even for estimating fundamental constants. In this talk, I will introduce how such quantum resources can enhance the estimation precision in various fundamental estimation tasks. In practice, however, quantum systems inevitably interact with their surrounding environments, leading to decoherence and the degradation of quantum resources. As a result, the system gradually transitions into a classical mixture, diminishing the achievable quantum advantage. To address this, I will also introduce recent advances in the application of quantum error correction and error mitigation—originally developed for quantum computation—to quantum metrology and restores the quantum-enhanced estimation.
3) Speaker: Lucas H. English ( Ph.D. student / University of Sydney)
Title: Quantum error correction and statistical mechanics
Abstract:
Decoding quantum error correcting (QEC) codes can be mapped to a problem in disordered statistical mechanics, where spin configurations encode possible errors and the threshold emerges as a phase transition. I will give a pedagogical introduction to this mapping and discuss how it reveals the role of disorder in determining the performance of topological codes. I will then introduce post-selection as a means of "cleaning out" this disorder by conditioning on favourable measurement outcomes. The talk will emphasize physical intuition, drawing on recent analytic and numerical results on scalable post-selection (arXiv:2410.07598,2510.05795, 2510.05222).
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