Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session S72: Quantum Error Correction III |
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Sponsoring Units: DQI Chair: Dany Lachance-Quirion, Nord Quantique Room: Room 406 |
Thursday, March 9, 2023 8:00AM - 8:12AM |
S72.00001: Error-correction zoo Victor V Albert, Philippe Faist Error correction is what ensures that the audio in your phone calls remains sharp, your hard drives do not deteriorate too quickly, and signals can be reliably transmitted to remote satellites. |
Thursday, March 9, 2023 8:12AM - 8:24AM |
S72.00002: Quantum Key Distribution over quantum repeater chains based on the hexagonal Gottesman-Kitaev-Preskill Code Debayan Bandyopadhyay, Filip D Rozpedek, Liang Jiang Quantum communication offers the possibility of generating secure cryptographic key over long distances, but the outstanding challenge is photon loss in optical fibers. To address this concern, repeaters utilizing both heralded and error-correcting schemes are studied. In error-correction, a particular class of bosonic codes provides strong resistance to photon loss errors. These are the Gottesman-Kitaev-Preskill (GKP) codes, of which the square and hexagonal lattice codes have been thoroughly examined. Previous works demonstrated how the square GKP code can be used for communication, leveraging analog syndrome data for post-selection and for concatenation with discrete-variable codes. Alternatively, the hexagonal code was shown to produce greater fidelity, and to heuristically correspond to an optimal encoding. However, it is not known how hexagonal GKP performs in repeater-based architectures in generating secret key rate relative to the square lattice based code. To address this gap, we consider the task of Quantum Key Distribution performed over a repeater chain based on the hexagonal lattice GKP code, comparing the secret key rate and achievable distance with the secret key generation of the square based code. We show that hexagonal GKP generally outperforms the square code both in secret key rate and achievable distance, examine how the hexagonal code performs in imperfect hardware, and analyze the benefit of techniques such as post-selection and advantage distillation in this context. |
Thursday, March 9, 2023 8:24AM - 8:36AM |
S72.00003: Passive two-photon dissipation for bit-flip error correction of a cat code Antoine Marquet, Antoine Essig, Nathanael Cottet, Anil Murani, Emanuele Albertinale, Jérémie Guillaud, Theau Peronnin, Sebastion Jezouin, Benjamin Huard, Raphael Lescanne Bosonic codes offer a resource-efficient method to quantum error correction. Of particular |
Thursday, March 9, 2023 8:36AM - 8:48AM |
S72.00004: Highly accurate decoder for topological color codes with simulated annealing Yugo Takada, Yusaku Takeuchi, Keisuke Fujii Quantum error correction is an essential ingredient for reliable quantum computation for theoretically provable quantum speedup. Topological color codes, one of the quantum error-correction codes, have an advantage against the surface codes in that all Clifford gates can be implemented transversally. However, hardness of decoding makes the color codes not suitable as the best candidate for experimentally feasible implementation of quantum error correction. Here we propose a highly accurate decoding scheme for the color codes using simulated annealing. In this scheme, we map stabilizer operators to classical spin variables to represent an error satisfying the syndrome. Then we construct an Ising Hamiltonian that counts the number of errors and formulate the decoding problem as an energy minimization problem of an Ising Hamiltonian, which is solved by simulated annealing. In numerical simulations on the square-octagon lattice, we find an error threshold of 10.5% for bit flip noises and 18.3% for depolarizing noises, both of which are higher than the thresholds of existing decoding algorithms. Furthermore, we verify that the achieved logical error probabilities are almost optimal in the sense that they are almost the same as those obtained by exact optimizations by CPLEX with much smaller decoding time. Since the decoding process has been a bottleneck for performance analysis, the proposed decoding method is useful for further exploration of possibility of the topological color codes. |
Thursday, March 9, 2023 8:48AM - 9:00AM |
S72.00005: Logical Majorana Fermions for Fault-Tolerant Quantum Simulation B. C. A Morrison, Andrew J Landahl We show how to absorb fermionic quantum simulation’s expensive fermion-to-qubit mapping overhead into the overhead already incurred by surface-code-based fault-tolerant quantum computing. The key idea is to process information in surface-code twist defects, which behave like logical Majorana fermions. Our approach encodes Dirac fermions, a key data type for simulation applications, directly into logical Majorana fermions rather than atop a logical qubit layer in the architecture. Using the 2D Fermi-Hubbard model as an exemplar, we show two applications of our approach that yield improvements in algorithms. First, by preserving the locality of fundamental fermionic operations, we can reduce the asymptotic circuit depth of a Trotter-Suzuki expansion of the time evolution operator. Second, by working in the paradigm of the Majorana fermion data type, we were able to obtain a T-count reduction for the block-encoding SELECT oracle that can be applied even without the use of the twist-defect/logical Majorana architecture described here. |
Thursday, March 9, 2023 9:00AM - 9:12AM |
S72.00006: Good Gottesman-Kitaev-Preskill Codes from the NTRU Cryptosystem Jonathan Conrad, Jens Eisert, Jean-Pierre Seifert Since their first experimental demonstrations [3, 5] bosonic Quantum-Error Correction with the Gottesman- Kitaev-Preskill (GKP) code [6] has seen a rapid increase of interest in experimental and theoretical investigations and has become a framework of interest in large scale quantum computing using photonics [1, 2] and supercon- ducting platforms [7]. While much research has been dedicated to obtain effective qubits from single-mode systems that are to be integrated into larger qubit-based networks, we argue that this approach is only scratching the surface of the potential quantum computing with the GKP code offers when compared to the more general, lattice theoretic perspective on these code [4, 9, 10]. To demonstrate this, we construct random good GKP codes derived from a cryptographic attack on the NTRU cryptosystem [8] and investigate the decoding problem of these codes. The presented scheme offers an example of a trapdoor decodable quantum error correcting code and is a first step towards cryptographic protocols built on the decoding problem of GKP codes which we believe can have wide application for secure quantum communication and cloud-based quantum computing. |
Thursday, March 9, 2023 9:12AM - 9:24AM |
S72.00007: A critical Schrodinger cat qubit Luca G Gravina, Fabrizio Minganti, Vincenzo Savona Encoding quantum information onto bosonic systems is a promising route to quantum error correction. In a cat code, this encoding relies on the confinement of the system’s dynamics onto the two-dimensional manifold spanned by Schrodinger cats of opposite parity. In dissipative cat qubits, an engineered dissipation scheme combining two-photon drive and two-photon dissipation has been used to autonomously stabilize this manifold, ensuring passive protection against, e.g., phase-flip errors regardless of their origin. Similarly, in Kerr cat qubits, where highly-performing gates can be engineered, two-photon drive and Kerr nonlinearity cooperate to Hamiltonianly confine the system onto the cat manifold. |
Thursday, March 9, 2023 9:24AM - 9:36AM |
S72.00008: Discrete optimization in the MPS-MPO language Aleksandr Berezutskii, Stefanos Kourtis, Christopher T Chubb In discrete optimization problems, one usually asks for an optimal object from a finite set. Such problems appear in many fields ranging from transportation and logistics to computational biology and quantum error correction. Many of these are NP-complete, making exact solutions too hard to find and thus leaving a battle field for different approximate algorithms. In the current study, we show how to marry the formulation of such problems with tensor networks and show relevant examples including decoding of quantum error correcting codes by virtue of approximate MPS-MPO contraction and DMRG-like algorithm. The code for the study is publicly available as a Python package. |
Thursday, March 9, 2023 9:36AM - 9:48AM |
S72.00009: Graph neural network decoders for stabilizer codes Moritz Lange, Pontus Havstrom, Valdemar Bergentall, Karl Hammar, Olivia Heuts, Basudha Srivastava, Evert van Nieuwenburg, Mats Granath We explore the use of convolutional graph neural networks (GNN) as decoders for error correcting topological stabilizer codes. The syndrome corresponding to stabilizer violations due to qubit errors is mapped to a graph with node and edge features. In contrast to the standard graph decoder algorithms based on minimum weight matching, the decoder find its own graph algorithm through extensive training using randomly generated error configurations. The neural network acts as a graph classifier, mapping the syndrome-graph to the most likely equivalence class of errors. We find that the GNN can outperform MWPM for depolarizing noise, but is also readily adaptable to biased noise and individualized qubit fidelities. Using limited connectivity graphs, the decoder complexity scales favorably with the code distance. This type of decoder can also potentially be trained in a model free context, using experimental stabilizer code data. |
Thursday, March 9, 2023 9:48AM - 10:00AM |
S72.00010: Suppressing the Accumulation of Leakage in Superconducting Circuits for Quantum Error Correction Nathan Lacroix, Luca Hofele, Ants Remm, Christoph Hellings, François Swiadek, Stefania Lazar, Colin Scarato, Dante Colao Zanuz, Michael Kerschbaum, Graham J Norris, Mohsen Bahrami Panah, Alexander Flasby, Sebastian Krinner, Andreas Wallraff Despite recent progress in experimental error correction realizations, quantum computers require lower error rates to reach the fault-tolerant regime in which they can outperform standard computers in computational tasks such as simulating quantum systems. One of the dominant errors limiting the performance of quantum error correction codes across multiple technology platforms is leakage out of the computational subspace, originating from the inherent multi-level structure of qubit implementations. In this talk, we present experimental progress towards the mitigation of leakage in targeted experiments with superconducting circuits. |
Thursday, March 9, 2023 10:00AM - 10:12AM |
S72.00011: Towards improving decoder performance with machine learned open quantum system simulations Arshpreet S Maan, Vikas Garg, Alexandru Paler Achieving resource efficient (ie. using a low number of physical qubits), large-scale error-corrected quantum computations will require good models of the noise to be mitigated by quantum error-correcting codes. Current models are mostly based on straightforward assumptions (e.g. depolarizing noise). Classical neural networks have been shown to be capable of abstracting the dynamics of quantum systems. |
Thursday, March 9, 2023 10:12AM - 10:24AM |
S72.00012: Decoding syndrome measurements in a distance-three surface code Sebastian Krinner, Ants Remm, Elie Genois, Nathan Lacroix, Christoph Hellings, Stefania Lazar, François Swiadek, Alexandre Blais, Christopher Eichler, Andreas Wallraff Successful and close-to-optimal decoding of error syndromes in the surface code requires a thorough understanding of the errors occurring while executing error correction cycles. Only then can a decoder associate each error syndrome with its most likely error class. Here we present a scheme based on the correlation analysis by Spitz et al. [1] to extract physical error probabilites per cycle directly from surface code experiments. We use the measured error rates to optimally set the weights in a minimum-weight-perfect-matching decoder used to correct errors in our quantum memory experiments [2]. Analyzing beyond-nearest-neighbor correlations between syndrome elements allows us to extend our understanding of different error sources. |
Thursday, March 9, 2023 10:24AM - 10:36AM |
S72.00013: Simulation of Error Correction in Atomic Array Quantum Computers Daniel Crow Atomic arrays of neutral have emerged as a promising platform for scalable quantum computation. In this talk we will present a framework for simulating coherent operations in neutral-atom qubits and discuss the physical errors specific to nuclear spin qubits in alkaline-earth atoms. Building on this, we discuss progress towards design of logical circuits on an error-corrected neutral atom quantum computer, including simulations and decoding strategies specific to error mechanisms in neutral atom qubits. |
Thursday, March 9, 2023 10:36AM - 10:48AM |
S72.00014: Machine-Learning-Assisted Quantum Error Correction Francisco Revson Fernandes Pereira, Martin Leib Fault-tolerant and scalable quantum computers rely on the use of QEC codes. QEC codes can be constructed and designed for classes of quantum channels. There are at least two challenges in designing QEC codes. Firstly, most phenomenological-modeling quantum channels are time-dependent. Secondly, state-of-the-art quantum physical systems have abundant sources of noise, making the design of near-optimal QEC codes an extremely demanding and challenging task. One possibility to solve this problem is using two error correction layers. Algebraic QEC codes and QNNs serve as interesting candidates for the first and second layers. |
Thursday, March 9, 2023 10:48AM - 11:00AM |
S72.00015: Improving syndrome detection using quantum optimal control Gavin S Hartnett, Pranav S Mundada, Yuval Baum, Ashish Kakkar, Tom Stace In order to achieve fault-tolerant quantum computation, it will be necessary to continuously correct errors using quantum error correcting codes. To meet this goal, it will be crucial to continue to develop better codes and decoders, as well as to improve the implementations of basic building blocks of error correction, such as stabilizer circuits and parity check operations, on real NISQ-stage devices available today. Here, we present recent results along these lines. First, we demonstrate that the fidelity of small-scale quantum error correcting codes can be improved using our deterministic error-suppression workflow, which is designed to reduce non-Markovian noise from a variety of sources using error-aware compilation, system-wide gate optimization, dynamical decoupling, and measurement-error mitigation. Results obtained using our workflow are consistently better than the default pipeline: we find improved error detection success rates which are 2.5 and 3.3 times higher compared to the default approach. Second, we introduce a faster implementation of the 2-qubit parity check operation and then use quantum optimal control techniques to calibrate this operation. This approach allows for improved parity checks that have both a higher fidelity and shorter duration than the standard implementation based on multiple two-qubit controlled gates. |
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