Please join us for the QSE Center Quantum Seminar with Robin Blume-Kohout from Sandia National Labs who will give the talk \"Assessing performance of logical operations with detector error models\" and Benoit Vermersch from Quobly and UGA who will give the talk \"Randomized measurements for large-scale quantum experiments\" on Friday April 24 from 11:30 to 13:30.
\r\nLocation: GR B3 30
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\r\n11:30-12:20 Benoit Vermersch
\r\n12:20-12:40: Pizza lunch
\r\n12:40-13:30: Robin Blume-Khout
\r\nAll PhDs, postdocs, students, group leaders, and PIs are welcome to join us.
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\r\nABSTRACT:
\r\n1. \"Assessing performance of logical operations with detector error models\" - Robin Blume-Kohout
\r\nQuantum computing is rapidly transitioning from the “NISQ” paradigm in which circuits and gates are executed directly on physical qubits to a fault tolerant “FTQC” paradigm in which circuits and gates are executed on encoded, error-corrected logical qubits. We want to model errors in gates. Logic gates on physical qubits are modeled by process matrices, derived from theory or estimated from tomography. But describing logical gates on logical qubits demands a richer model — specifically, detector error models — that can describe QEC syndrome data. I’ll introduce detector error models and summarize three recent papers in which we show how to estimate detector error models from data [https://arxiv.org/abs/2504.14643], how to simulate arbitrary small Markovian errors in Clifford circuits [https://arxiv.org/abs/2504.15128], and how to generate detector error models from arbitrary circuit-level Markovian errors [https://arxiv.org/abs/2603.18457].
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\r\n2. \"Randomized measurements for large-scale quantum experiments\" - Benoit Vermersch
\r\nThe randomized measurements toolbox is now routinely used in quantum experiments to estimate fundamental quantum properties, such as entanglement [1].
\r\nWhile experimentalists appreciate the simplicity and robustness aspects of such measurement protocols, a challenge for theorists is to design strategies for overcoming statistical errors using \"cheap\" polynomial resources in system size.
\r\nIn this context, I will present recent upgrades to the randomized measurements toolbox that address this challenge for large-scale quantum states that are relevant to the field of quantum simulation. In particular, I will discuss efficient protocols for measuring entanglement [2] and performing state tomography [3].
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\r\n[1] A. Elben, S. T. Flammia, H.-Y. Huang, R. Kueng, J. Preskill, B. Vermersch, and P. Zoller, The Randomized Measurement Toolbox, Nat Rev Phys 5, 9 (2022).
\r\n[2] B. Vermersch, M. Ljubotina, J. I. Cirac, P. Zoller, M. Serbyn, and L. Piroli, Many-Body Entropies and Entanglement from Polynomially Many Local Measurements, Phys. Rev. X 14, 031035 (2024).
\r\n[3] M. Votto, M. Ljubotina, C. Lancien, J. Ignacio Cirac, P. Zoller, M. Serbyn, L. Piroli, B. Vermersch, arXiv:2507.12550
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\r\nBIOS:
\r\nRobin Blume-Kohout was born on a kitchen table in the Alaska Bush almost (but not quite) 50 years ago. Unfortunately, things went downhill thereafter. He is now the founder and codirector of Sandia’s Quantum Performance Lab (QPL), where he and his fellow malcontents dream up new ways to assess and enhance the performance of quantum computers and their components.
\r\nBenoit Vermersch is an associate professor at the University of Grenoble Alpes, member of the LPMMC currently on leave in the quantum startup Quobly Research interests include implementations of quantum processing units with cold atoms, trapped ions, superconducting qubits; measurement protocols for entanglement-related quantities, out-of-time ordered correlators, topological invariants; many-body entanglement theory; quantum networks: Light-matter interfaces, quantum state transfer protocols, waveguide quantum electrodynamics; and tensor-network numerical methods: Matrix-Product-States and DMRG,TEBD related algorithms.
Please join us for the QSE Center Quantum Seminar with Johannes Zeiher from the LMU Munich who will give a talk about \"Quantum computing with metastable atomic qubits\" on Friday May 8 from 12pm to 1:30pm.
\r\nLocation: BS 150
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\r\nPizzas will be available at 12:00. All PhDs, postdocs, students, group leaders, and PIs are welcome to join us.
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\r\nTITLE: \"Quantum computing with metastable atomic qubits\"
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\r\nABSTRACT:
\r\nAtom arrays have shaped the research frontiers of quantum simulation, quantum metrology, and quantum computation in recent years. In this talk, I will present our approach to quantum computing utilizing metastable fine-structure qubits in bosonic strontium atoms. Combining long coherence times, high-fidelity gates, and coherent atom shuttling with THz-scale qubit splitting, we realize a powerful computational platform featuring a natural implementation of logical qubits. Leveraging velocity-selective addressing of individual atoms enables mid-circuit readout or resets, opening the path to cyclic error correction or measurement-based quantum computing. Furthermore, I will present our approach to scaling atom arrays based on directly loaded large-scale optical lattices. Utilizing a specialized, highly anisotropic lattice geometry, we directly load thousands of individually addressable strontium atoms from the magneto-optical trap and demonstrate continuous replenishment of atoms in the system. Our work establishes the fine-structure qubit in strontium as a promising qubit platform for neutral-atom quantum computers and showcases the scalability of atom arrays trapped in optical lattices.
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\r\nBIO:
\r\nJohannes Zeiher studied physics at the LMU Munich and the University of Cambridge, where he obtained his masters degree in 2012. He did his PhD in the group of Immanuel Bloch at MPQ, focusing on quantum simulations with neutral atoms in optical lattices, in particular employing highly excited Rydberg states for realizing quantum spin models. For this work, he received the Otto Hahn Medal of the Max Planck Society. Following his postdoc as a Feodor Lynen Fellow at UC Berkeley with Dan Stamper-Kurn on single-atom cavity QED, in 2020 he joined the Quantum Many-Body Systems Division at MPQ as a research group leader. Since 2022, he leads the independent research group “Quantum Matter Interfaces” at MPQ, which is supported by the BMBF through the Quantum Future program for Junior Research Groups. Since 2025, Johannes is a Professor for Synthetic Quantum Matter at the LMU Munich. His research focuses on quantum computing, quantum gas microscopy of many- and few-body systems in optical lattices and novel light-matter interfaces.
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