SQuInT 2022 Program
Full Program | Thursday | Friday | Saturday | All Sessions | Posters | Talks
SESSION 10: Superconducting quantum computing (Islands Ballroom)Chair: (Tameem Albash (UNM)) | |
| 8:30 am - 9:15 am | Andreas Wallraff, ETH Zurich (invited) Quantum Error Correction in a Surface Code with Superconducting Circuits | Abstract. Superconducting electronic circuits are ideally suited for studying quantum physics and its applications. Since complex circuits containing hundreds or thousands of elements can be designed, fabricated, and operated with relative ease, they are one of the prime contenders for realizing quantum computers. Currently, both academic and industrial labs vigorously pursue the realization of universal fault-tolerant quantum computers. However, building systems which can address commercially relevant computational problems continues to require significant conceptual and technological progress. For fault-tolerant operation quantum computers must correct errors occurring due to unavoidable decoherence and limited control accuracy. Here, we demonstrate quantum error correction using the surface code, which is known for its exceptionally high tolerance to errors. Using 17 physical qubits in a superconducting circuit (see Figure 1) we encode quantum information in a distance-three logical qubit building up on our recent distance-two error detection experiments [1]. In an error correction cycle taking only 1.1 µs, we demonstrate the preservation of four cardinal states of the logical qubit. Repeatedly executing the cycle, we measure and decode both bit- and phase-flip error syndromes using a minimum-weight perfect-matching algorithm in an error-model-free approach and apply corrections in postprocessing. We find a low logical error probability of 3 % per cycle [2]. The measured characteristics of our device agree well with a numerical model. Our demonstration of repeated, fast, and high-performance quantum error correction cycles, together with recent advances in ion traps, support our understanding that fault-tolerant quantum computation will be practically realizable. |
| 9:15 am - 9:45 am | Maxime Dupont, Rigetti Computing How hard is it to outperform a classical simulator at running a quantum optimization algorithm? | Abstract. Platforms for studying variational quantum-classical algorithms (VQAs) with superconducting qubit processors reaching beyond the limits of exascale emulation limits are on the horizon. In this talk, we review recent work on one pattern of VQA, the QAOA anstaz. First, we refine expected boundaries for scaling up noisy simulation with QAOA with tensor networks, limited by entanglement. Still, initial states and final solutions with QAOA typically have low entanglement. We thus clarify the evolution of entanglement during the execution of the algorithm. Next, we report QAOA runs on the recent Aspen-M 80Q platform at Rigetti. We highlight the role of error mitigation for tailoring hardware noise at scale. |
| 9:45 am - 10:15 am | Aleksander Kubica, AWS Center for Quantum Computing Erasure qubits: Overcoming the T1 limit in superconducting circuits | Abstract. The amplitude damping time, T_1, has long stood as the major factor limiting quantum fidelity in superconducting circuits, prompting concerted efforts in the material science and design of qubits aimed at increasing T_1. In contrast, the dephasing time, T_\phi, can usually be extended above T_1 (via, e.g., dynamical decoupling), to the point where it does not limit fidelity. In this article we propose a scheme for overcoming the conventional T_1 limit on fidelity by designing qubits in a way that amplitude damping errors can be detected and converted into erasure errors. Compared to standard qubit implementations our scheme improves the performance of fault-tolerant protocols, as numerically demonstrated by the circuit-noise simulations of the surface code. We describe two simple qubit implementations with superconducting circuits and discuss procedures for detecting amplitude damping errors, performing entangling gates, and extending T_\phi. Our results suggest that engineering efforts should focus on improving T_\phi and the quality of quantum coherent control, as they effectively become the limiting factor on the performance of fault-tolerant protocols. |
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SQuInT Chief Organizer
Akimasa Miyake, Associate Professor
amiyake@unm.edu
SQuInT Co-Organizer
Hartmut Haeffner, Associate Professor, UC Berkeley
hhaeffner@berkeley.edu
SQuInT Administrator
Dwight Zier
d29zier@unm.edu
505 277-1850
SQuInT Program Committee
Alberto Alonso, Postdoc, UC Berkeley
Philip Blocher, Postdoc, UNM
Neha Yadav, Postdoc, UC Berkeley
Cunlu Zhou, Postdoc, UNM
SQuInT Founder
Ivan Deutsch, Regents' Professor, CQuIC Director
ideutsch@unm.edu
