• Program

[Jul. 27 (Monday)]--------------------------------------------------------------------------------------------------------------

Talk 1: 조성주(서울대학교): Autonomous quantum error correction of the spin-oscillator hybrid qubits

Protecting quantum states from decoherence is a quintessential task in both the fundamental study of quantum information and its practical applications. However, preserving quantum information is more challenging than preserving classical information, as syndrome measurements required for detecting and correcting errors can cause additional decoherence. Autonomous quantum error correction (AutoQEC) proposes a measurement-free alternative to protect quantum information by designing a passive channel to stabilize the code space. Such a channel can be realized via engineered dissipation by coupling the system to a highly dissipative bath system. 

In this work, we propose a novel continuous-variable-discrete-variable (CV–DV) hybrid AutoQEC protocol that effectively suppresses phase noise in both DV spin and CV oscillator systems using a single jump operator. Our formalism provides exponential suppression of phase noise from both the spin and oscillator systems, which is implementable with elements already realized in experimental platforms such as the trapped-ion systems. The resulting noise-biased hybrid qubits provide a promising resource for concatenated quantum error correction and quantum metrology.

Lecture 1: 이재학(KIST): Basic principles of quantum error correction

Quantum error correction (QEC) provides a fundamental framework for protecting quantum information from environmental noise and decoherence. We begin with the three-qubit error-correction code as a simple example to illustrate the essential ideas of error correction. This lecture introduces the basic principles of QEC, with an emphasis on the physical intuition and mathematical foundations that enable the reliable protection of quantum information. Topics include the characterization of quantum errors, the conditions for error correction, and syndrome extraction. The lecture also discusses the concepts of code distance and error-correction thresholds, providing the conceptual foundation for fault-tolerant quantum computing.

[Poster Session]

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[Jul. 28 (Tuesday)]---------------------------------------------------------------------------------------------------------

Talk 2: 손본(KAIST): When to Skip Syndrome Extraction in Surface-GKP Codes

In standard fault-tolerant quantum error correction, repeated syndrome measurements are necessary to correct errors induced by the syndrome extraction process itself. However, such repetition incurs substantial overhead in terms of the number of gates and ancilla consumption (e.g., GKP states), and can introduce additional errors into the system. To address these issues, we propose a dynamic syndrome measurement-skipping scheme for concatenated surface-GKP codes that utilizes analog information in continuous-variable systems. The key idea is to dynamically determine whether each syndrome extraction round is necessary by estimating the expected syndrome information gain and the measurement confidence from the analog outcomes of the GKP qubits. Our strategy reduces overhead and mitigates error propagation during syndrome extraction by skipping rounds predicted to yield trivial syndromes. Numerical simulations demonstrate that when idle noise is lower than gate and measurement noise, we achieve significantly lower logical error rates than the standard non-skipping baseline, even when skipping most of the syndrome extraction rounds. These results suggest that our strategy helps reduce the demand for GKP state generation by lowering ancilla consumption during syndrome extraction while achieving lower logical error rates, thereby relaxing the hardware requirements for achieving fault tolerance.

Talk 3: 김영빈(KAIST): Pulse-Driven Nonlinear Quantum Photonics in Integrated Platforms

Nonlinear quantum optics is essential for generating nonclassical light and coherently manipulating quantum states. With the rapid development of integrated quantum photonics, tight optical confinement and compact device architectures provide new opportunities for nonlinear light sources and high-gain quantum optical processes. Here, we present PHOQUS, a generalized transfer-matrix simulator for nonlinear quantum optics in integrated photonic platforms target to pulsed-driven regime. PHOQUS enables non-perturbative modeling of high-gain regimes, noisy processes, and unwanted nonlinear interactions through modular components such as waveguides, ring resonators, and detectors. This framework can be used to design and understand nonlinear photonic systems, construct more complex quantum photonic architectures, and predict or optimize unexpected physical phenomena.

Lecture 2: 이석형(SKKU): Advanced topics in quantum error correction

Building on the basic principles introduced in Lecture 1, this lecture develops the stabilizer formalism as a unifying language for modern quantum error correction and fault-tolerant quantum computing. We discuss how quantum codes are constructed and analyzed using stabilizer generators, syndromes, logical operators, and code distance, with the surface code as a central example. The lecture then introduces several key ingredients of fault tolerance, including transversal gates, lattice surgery, decoding, and magic state distillation for implementing non-Clifford operations. Emphasis is placed on how these concepts fit together in scalable architectures, connecting the abstract theory of quantum error correction to practical strategies for reliable quantum computation.

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[Jul. 29 (Wednesday)]--------------------------------------------------------------------------------------------------

Lecture 3: 손영익(KAIST): Physical Origins of Quantum Errors in Photonic Quantum Computing

Unlike other quantum computing platforms, photonic quantum computing does not have well-defined metrics for conventional gate errors, such as single-qubit and two-qubit gate error rates. This is because, in the absence of deterministic nonlinear interactions, photonic quantum computing relies on measurement-based quantum computing (MBQC), where large-scale cluster states are generated through inherently probabilistic fusion operations. Consequently, understanding the physical origins of computational errors requires a different framework from the gate-error metrics commonly used for other quantum hardware. In this talk, I will present the dominant error models associated with realistic photonic hardware, including imperfections in single-photon sources and fusion operations, and discuss how these physical error mechanisms translate into logical errors in photonic quantum computing.