[Landau ITP Seminars] Thursday 21.05.2026 - ITP/CAS Colloquium

[info+seminars at itp.ac.ru]

Уважаемые коллеги!

На онлайн коллоквиум по теоретической физике в четверг 21.05 будут заслушаны 2 доклада:

1) 10:00:00 по московскому времени: Pan Zhang (Institute of Theoretical Physics, Chinese Academy of Sciences)
Decoding of Quantum Error-Correcting Codes: From Exact Spin Glass Solution to Neural Network Decoder, Then to Quantum-Circuit Decoder

The talk first shows how optimal maximum-likelihood decoding for certain quantum error-correcting codes (e.g., surface code with independent qubit noise, repetition code under circuit-level noise) maps to exact computation of the partition function of planar spin glasses, yielding a polynomial-time exact decoder. Next, a more general decoding framework based on generative neural networks is presented, followed by a faster variational quantum-circuit counterpart that can run on quantum hardware without syndrome measurements.

Biography: 

Pan Zhang is Professor and Director of the Second Research Division at ITP-CAS. Research: statistical physics, quantum physics, machine learning. Proposed sparse-state tensor network method (resolved Google Sycamore sampling problem); introduced Variational Autoregressive Networks (VAN) and Matrix Product State (MPS) Born machine. Honors: Young Scientist Award of CAS (2023), Second Prize of Beijing Natural Science Award (2022). Since 2023, Divisional Associate Editor (DAE) for Physical Review Letters (physics and machine learning section).



2) 10:00:00 по московскому времени: Yuriy Makhlin (L. D. Landau Institute for Theoretical Physics, Russian Academy of Sciences)
Topological Josephson Junctions and Quantum Computations

Josephson vortices in planar superconducting junctions on top of a topological insulator material may bind electronic states. These subgap states include Majorana modes at zero energy. Their position can be controlled via magnetic field and phase bias, enabling coherent manipulation of quantum states and quantum information processing. Recent experimental data on supercurrent in planar topological Josephson junctions show features possibly linked to low-energy subgap modes. The talk discusses how these modes may explain observed behavior and how interference of local Josephson currents can be used to demonstrate Majorana zero modes and probe their quantum state. Analysis includes disorder effects and other methods to probe bound states, including spectroscopy.

Biography: 

Yuriy Makhlin earned his PhD (1995) and Doctor of Sciences (2004) from the Landau Institute. Research interests: quantum computation, superconducting qubits, quantum circuits, topological materials. Postdoc at UIUC and Karlsruhe; led a research group at University of Karlsruhe (2001–2004) as Sofya Kovalevskaya awardee. Corresponding member of Russian Academy of Sciences; received Fock prize (2018).