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What is the minimum number of extra qubits needed to perform a large fault-tolerant quantum circuit? Working in a common model of fault-tolerance, I show that in the asymptotic limit of large circuits, the ratio of physical qubits to…

Quantum Physics · Physics 2014-07-23 Daniel Gottesman

Running quantum algorithms protected by quantum error correction requires a real time, classical decoder. To prevent the accumulation of a backlog, this decoder must process syndromes from the quantum device at a faster rate than they are…

Quantum Physics · Physics 2025-04-01 Sophia Fuhui Lin , Eric C. Peterson , Krishanu Sankar , Prasahnt Sivarajah

Quantum computers have the potential to change the way we solve computational problems. Due to the noisy nature of qubits, the need arises to correct physical errors occurring during computation. The surface code is a promising candidate…

Quantum Physics · Physics 2024-05-06 Gyorgy P. Geher , Ophelia Crawford , Earl T. Campbell

Constant-rate low-density parity-check (LDPC) codes are promising candidates for constructing efficient fault-tolerant quantum memories. However, if physical gates are subject to geometric-locality constraints, it becomes challenging to…

Quantum Physics · Physics 2025-05-07 Christopher A. Pattison , Anirudh Krishna , John Preskill

Reliable qubits are difficult to engineer, but standard fault-tolerance schemes use seven or more physical qubits to encode each logical qubit, with still more qubits required for error correction. The large overhead makes it hard to…

Quantum Physics · Physics 2018-11-02 Rui Chao , Ben W. Reichardt

With fault-tolerant quantum computing (FTQC) on the horizon, it is critical to understand sources of logical error in plausible hardware implementations of quantum error-correcting codes (QECC). In this work, we consider logical error rates…

Designs for quantum error correction depend strongly on the connectivity of the qubits. For solid state qubits, the most straightforward approach is to have connectivity constrained to a planar graph. Practical considerations may also…

Quantum Physics · Physics 2024-12-17 Bence Hetényi , James R. Wootton

We investigate the construction of quantum low-density parity-check (LDPC) codes from classical quasi-cyclic (QC) LDPC codes with girth greater than or equal to 6. We have shown that the classical codes in the generalized…

Quantum Physics · Physics 2010-02-11 Min-Hsiu Hsieh , Todd A. Brun , Igor Devetak

Quantum low-density parity-check (QLDPC) codes with good parameters are promising candidates for low-overhead fault-tolerant quantum computing, but their non-local stabilizers require long-range connectivity and frequent qubit movement,…

Quantum Physics · Physics 2026-04-29 Swayangprabha Shaw , Narayanan Rengaswamy

Several notions of code products are known in quantum error correction, such as hyper-graph products, homological products, lifted products, balanced products, to name a few. In this paper we introduce a new product code construction which…

Quantum Physics · Physics 2024-07-24 Dimiter Ostrev , Davide Orsucci , Francisco Lázaro , Balazs Matuz

Quantum error correction offers a promising path for performing quantum computations with low errors. Although a fully fault-tolerant execution of a quantum algorithm remains unrealized, recent experimental developments, along with…

We propose fault-tolerant encoders for quantum low-density parity check (LDPC) codes. By grouping qubits within a quantum code over contiguous blocks and applying preshared entanglement across these blocks, we show how transversal…

Quantum Physics · Physics 2024-05-27 Abhi Kumar Sharma , Shayan Srinivasa Garani

Quantum error correction is the building block for constructing fault-tolerant quantum processors that can operate reliably even if its constituting elements are corrupted by decoherence. In this context, real-time decoding is a necessity…

Quantum Physics · Physics 2024-02-15 Antonio deMarti iOlius , Josu Etxezarreta Martinez

Benchmarking physical devices and verifying logical algorithms are important tasks for scalable fault-tolerant quantum computing. Numerous protocols exist for benchmarking devices before running actual algorithms. In this work, we show that…

Quantum Physics · Physics 2026-02-05 Xiao Xiao , Dominik Hangleiter , Dolev Bluvstein , Mikhail D. Lukin , Michael J. Gullans

Quantum computation must be performed in a fault-tolerant manner to be realizable in practice. Recent progress has uncovered quantum error-correcting codes with sparse connectivity requirements and constant qubit overhead. Existing schemes…

Quantum Physics · Physics 2026-04-20 Dominic J. Williamson , Theodore J. Yoder

Efficient and high-performance quantum error correction is essential for achieving fault-tolerant quantum computing. Low-depth random circuits offer a promising approach to identifying effective and practical encoding strategies. In this…

Quantum Physics · Physics 2026-03-02 Guoding Liu , Zhenyu Du , Zi-Wen Liu , Xiongfeng Ma

Modular architectures are a promising approach to scaling quantum computers to fault tolerance. Small, low-noise quantum processors connected through relatively noisy quantum links are capable of fault-tolerant operation as long as the…

Quantum Physics · Physics 2025-10-16 Trond Hjerpekjøn Haug , Timo Hillmann , Anton Frisk Kockum , Raphaël Van Laer

Quantum low-density parity-check (qLDPC) codes have emerged as a promising approach for realizing low-overhead logical quantum memories. Recent theoretical developments have established shift automorphisms as a fundamental building block…

Quantum Physics · Physics 2026-01-16 Younghun Kim , Spiro Gicev , Martin Sevior , Muhammad Usman

The ability to execute a large number of quantum gates in parallel is a fundamental requirement for quantum error correction, allowing an error threshold to exist under the finite coherence time of physical qubits. Recently, two-dimensional…

Quantum Physics · Physics 2025-01-20 Fangxuan Liu , Gaoxiang Tang , Luming Duan , Yukai Wu

We describe an experimental effort designing and deploying error-robust single-qubit operations using a cloud-based quantum computer and analog-layer programming access. We design numerically-optimized pulses that implement target…