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Quantum error correction is necessary to perform large-scale quantum computation, but requires extremely large overheads in both space and time. High-rate quantum low-density-parity-check (qLDPC) codes promise a route to reduce qubit…

Motivated by their central role in fault-tolerant quantum computation, we study the sets of gates of the third-level of the Clifford hierarchy and their distinguished subsets of `nearly diagonal' semi-Clifford gates. The Clifford hierarchy…

Quantum Physics · Physics 2024-05-30 Imin Chen , Nadish de Silva

Starting with an explicit framework for designing logical Clifford circuits for CSS codes, we construct logical gates for Hypergraph Product Codes. We first derive symplectic matrices for CNOT, CZ, Phase, and Hadamard operators, which…

Quantum Physics · Physics 2025-09-03 Adway Patra , Alexander Barg

Transversal logical gates offer the opportunity for fast and low-noise logic, particularly when interspersed by a single round of parity check measurements of the underlying code. Using such circuits for the surface code requires decoding…

Quantum Physics · Physics 2026-02-23 Marc Serra-Peralta , Mackenzie H. Shaw , Barbara M. Terhal

A major goal for fault-tolerant quantum computation (FTQC) is to reduce the overhead needed for error correction. One approach is to use block codes that encode multiple qubits, which can achieve significantly higher rates for the same code…

Quantum Physics · Physics 2015-04-16 Todd A. Brun , Yi-Cong Zheng , Kung-Chuan Hsu , Joshua Job , Ching-Yi Lai

Transversal gates play a crucial role in suppressing error propagation in fault-tolerant quantum computation, yet they are intrinsically constrained: any nontrivial code encoding a single logical qubit admits only a finite subgroup of…

Quantum Physics · Physics 2025-04-30 Chao Zhang , Zipeng Wu , Shilin Huang , Bei Zeng

CSS codes are a subfamily of stabilizer codes especially appropriate for fault-tolerant quantum computations. A very simple method is proposed to encode a general qudit when a Calderbank-Shor-Steane quantum code, defined over a q-ary…

Quantum Physics · Physics 2007-12-20 Pedro J. Salas

We describe a method to use measurements and correction operations in order to implement the Clifford group in a stabilizer code, generalising a result from [Bombin,2011] for topological subsystem colour codes. In subsystem stabilizer codes…

Quantum Physics · Physics 2025-02-10 Darren Banfield , Heather Leitch , Alastair Kay

Flag qubits have recently been proposed in syndrome extraction circuits to detect high-weight errors arising from fewer faults. The use of flag qubits allows the construction of fault-tolerant protocols with the fewest number of ancillas…

Quantum Physics · Physics 2020-01-27 Theerapat Tansuwannont , Christopher Chamberland , Debbie Leung

It is the prevailing belief that quantum error correcting techniques will be required to build a utility-scale quantum computer able to perform computations that are out of reach of classical computers. The QECCs that have been most…

We give an asymptotically good family of quantum CSS codes on qubits with a transversal CCZ gate, meaning that the parallel logical CCZ on all logical qubits is performed by parallel physical CCZs on (a subset of) physical qubits. The…

Quantum Physics · Physics 2024-10-15 Quynh T. Nguyen

In this paper, we focus on the problem of computing the set of diagonal transversal gates fixing a CSS code. We determine the logical actions of the gates as well as the groups of transversal gates that induce non-trivial logical gates and…

Information Theory · Computer Science 2026-01-30 Eduardo Camps-Moreno , Hiram H. López , Gretchen L. Matthews , Narayanan Rengaswamy , Rodrigo San-José

Given some group $G$ of logical gates, for instance the Clifford group, what are the quantum encodings for which these logical gates can be implemented by simple physical operations, described by some physical representation of $G$? We…

Quantum Physics · Physics 2025-02-10 Aurélie Denys , Anthony Leverrier

Utility-scale quantum computing requires quantum error correction (QEC) to protect quantum information against noise. Currently, superconducting hardware is a promising candidate for achieving fault tolerance due to its fast gate times and…

Quantum Physics · Physics 2025-08-06 György P. Gehér , David Byfield , Archibald Ruban

Quantum low-density parity-check (qLDPC) codes are a promising construction for drastically reducing the overhead of fault-tolerant quantum computing (FTQC) architectures. However, all of the known hardware implementations of these codes…

Recently, Bravyi and K\"onig have shown that there is a tradeoff between fault-tolerantly implementable logical gates and geometric locality of stabilizer codes. They consider locality-preserving operations which are implemented by a…

Quantum Physics · Physics 2015-01-14 Fernando Pastawski , Beni Yoshida

Transversal gates are the simplest form of fault-tolerant gates and are relatively easy to implement in practice. Yet designing codes that support useful transversal operations -- especially non-Clifford or addressable gates -- remains…

Quantum Physics · Physics 2026-03-05 ChunJun Cao , Brad Lackey

To build large-scale quantum computers while minimizing resource requirements, one may want to use high-rate quantum error-correcting codes that can efficiently encode information. However, realizing an addressable gate$\unicode{x2014}$a…

Quantum Physics · Physics 2026-02-18 Theerapat Tansuwannont , Tim Chan , Ryuji Takagi

We present an architecture for early fault-tolerant quantum computers based on the smallest interesting colour code (Earl Campbell, 2016). It realizes a universal logical gate set consisting of single-qubit measurements and preparations in…

Quantum Physics · Physics 2025-07-29 Jacob S. Nelson , Andrew J. Landahl , Andrew D. Baczewski

The Gottesman-Kitaev-Preskill (GKP) code is an exciting route to fault-tolerant quantum computing since Gaussian resources and GKP Pauli-eigenstate preparation are sufficient to achieve universal quantum computing. In this work, we provide…

Quantum Physics · Physics 2024-04-08 Mackenzie H. Shaw , Andrew C. Doherty , Arne L. Grimsmo