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We show that universal quantum computation can be concretely made fault-tolerant without mid-circuit measurements. To this end, we introduce a measurement-free deformation protocol of the Bacon-Shor code to realize a logical $\mathit{CCZ}$…

Quantum Physics · Physics 2025-11-18 Stefano Veroni , Alexandru Paler , Giacomo Giudice

Code switching is an established technique that facilitates a universal set of FT quantum gate operations by combining two QEC codes with complementary sets of gates, which each by themselves are easy to implement fault-tolerantly. In this…

Quantum Physics · Physics 2025-09-10 Sascha Heußen , Janine Hilder

The threshold theorem promises a path to fault-tolerant quantum computation, provided the physical error rate is below a critical threshold. While transversal gates efficiently implement logical operations, they propagate errors and can…

Quantum Physics · Physics 2026-04-21 Yichen Xu , Yiqing Zhou , James P. Sethna , Eun-Ah Kim

Quantum error mitigation techniques mimic noiseless quantum circuits by running several related noisy circuits and combining their outputs in particular ways. How well such techniques work is thought to depend strongly on how noisy the…

Quantum Physics · Physics 2026-02-12 David Layden , Bradley Mitchell , Karthik Siva

In this note we present explicit canonical forms for all the elements in the two-qubit CNOT-Dihedral group, with minimal numbers of controlled-S (CS) and controlled-X (CX) gates, using the generating set of quantum gates [X, T, CX, CS]. We…

Quantum Physics · Physics 2020-12-10 Shelly Garion , Andrew W. Cross

The state of the art of quantum circuits using the ripple-carry strategy for the addition and comparison of two n-bit numbers is presented, as well as optimizations in the Clifford+T gate set, both in terms of CNOT-depth and T-depth, or…

Quantum Physics · Physics 2024-05-29 Maxime Remaud

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

The paper discusses the gate complexity and the depth of reversible circuits consisting of NOT, CNOT and 2-CNOT gates in the case, when the number of additional inputs is limited. We study Shannon's gate complexity function $L(n, q)$ and…

Computational Complexity · Computer Science 2017-03-28 Dmitry V. Zakablukov

Because of their long coherence time and compatibility with industrial foundry processes, electron spin qubits are a promising platform for scalable quantum processors. A full-fledged quantum computer will need quantum error correction,…

The scarcity of qubits is a major obstacle to the practical usage of quantum computers in the near future. To circumvent this problem, various circuit knitting techniques have been developed to partition large quantum circuits into…

Quantum Physics · Physics 2023-11-01 Christophe Piveteau , David Sutter

The ability to implement the Quantum Fourier Transform (QFT) efficiently on a quantum computer facilitates the advantages offered by a variety of fundamental quantum algorithms, such as those for integer factoring, computing discrete…

Quantum Physics · Physics 2020-04-09 Yunseong Nam , Yuan Su , Dmitri Maslov

Quantum information science addresses how uniquely quantum mechanical phenomena such as superposition and entanglement can enhance communication, information processing and precision measurement. Photons are appealing for their low noise,…

Quantum Physics · Physics 2015-05-19 Ryo Okamoto , Jeremy L. O'Brien , Holger F. Hofmann , Shigeki Takeuchi

Modern platforms for potential qubit candidates, such as trapped ions or neutral atoms, allow long range connectivity between distant physical qubits through shuttling. This opens up an avenue for transversal logical CNOT gates between…

Quantum Physics · Physics 2025-04-14 Kwok Ho Wan , Mark Webber , Austin G. Fowler , Winfried K. Hensinger

Universal quantum computation may be realized based on quantum walk, by formulating it as a scattering problem on a graph. In this paper, we simulate quantum gates through electric circuits, following a recent report that a one-dimensional…

Mesoscale and Nanoscale Physics · Physics 2020-06-15 Motohiko Ezawa

Linear optical quantum computation (LOQC) offers a promising platform for scalable quantum information processing, but its scalability is fundamentally constrained by the probabilistic nature of non-local entangling gates. Qudit circuit…

Quantum Physics · Physics 2026-02-10 Apurav , Jaskaran Singh

To approximate arbitrary unitary transformations on one or more qubits, one must perform transformations which are outside of the Clifford group. The gate most commonly considered for this purpose is the T = diag(1, exp(i \pi/4)) gate. As T…

Quantum Physics · Physics 2020-05-04 Niel de Beaudrap , Xiaoning Bian , Quanlong Wang

We show that the depth of quantum circuits in the realistic architecture where a classical controller determines which local interactions to apply on the kD grid Z^k where k >= 2 is the same (up to a constant factor) as in the standard…

Quantum Physics · Physics 2013-05-09 David Rosenbaum

This work proposes numerical tests which determine whether a two-qubit operator has an atypically simple quantum circuit. Specifically, we describe formulae, written in terms of matrix coefficients, characterizing operators implementable…

Quantum Physics · Physics 2009-11-10 Vivek V. Shende , Stephen S. Bullock , Igor L. Markov

The Gottesman-Knill theorem asserts that a quantum circuit composed of Clifford gates can be efficiently simulated on a classical computer. Here we revisit this theorem and extend it to quantum circuits composed of Clifford and T gates,…

Quantum Physics · Physics 2019-04-11 Sergey Bravyi , David Gosset

We introduce a quantum-inspired approximation algorithm for MaxCut based on low-depth Clifford circuits. We start by showing that the solution unitaries found by the adaptive quantum approximation optimization algorithm (ADAPT-QAOA) for the…

Quantum Physics · Physics 2024-06-25 Manuel H. Muñoz-Arias , Stefanos Kourtis , Alexandre Blais