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The study of quantum circuits composed of commuting gates is particularly useful to understand the delicate boundary between quantum and classical computation. Indeed, while being a restricted class, commuting circuits exhibit genuine…

Quantum Physics · Physics 2013-03-19 Xiaotong Ni , Maarten Van den Nest

The term Clifford group was introduced in 1998 by D. Gottesmann in his investigation of quantum error-correcting codes. The simplest Clifford group in multiqubit quantum computation is generated by a restricted set of unitary Clifford gates…

Quantum Physics · Physics 2018-10-25 J. Tolar

By the Gottesman-Knill Theorem, the outcome probabilities of Clifford circuits can be computed efficiently. We present an alternative proof of this result for quopit Clifford circuits (i.e., Clifford circuits on collections of $p$-level…

Quantum Physics · Physics 2021-04-13 Dax Enshan Koh , Mark D. Penney , Robert W. Spekkens

Quantum circuit equivalence checking asks whether two circuits implement the same unitary. It guarantees compiler correctness and safe optimization, yet most existing approaches scale exponentially with the number of qubits or the circuit…

Quantum Physics · Physics 2026-03-16 Daisuke Sakamoto , Soshun Naito , Yusei Mori , Kosuke Mitarai

Kliuchnikov, Maslov, and Mosca proved in 2012 that a $2\times 2$ unitary matrix $V$ can be exactly represented by a single-qubit Clifford+$T$ circuit if and only if the entries of $V$ belong to the ring $\mathbb{Z}[1/\sqrt{2},i]$. Later…

Quantum Physics · Physics 2020-04-08 Matthew Amy , Andrew N. Glaudell , Neil J. Ross

Clifford circuit optimization is an important step in the quantum compilation pipeline. Major compilers employ heuristic approaches. While they are fast, their results are often suboptimal. Minimization of noisy gates, like 2-qubit CNOT…

Quantum Physics · Physics 2025-04-02 Irfansha Shaik , Jaco van de Pol

Classical simulations of quantum systems are notoriously difficult computational problems, with conventional state vector and tensor network methods restricted to quantum systems that feature only a small number of qudits. The recently…

Quantum Physics · Physics 2026-01-28 Ben Harper , Azar C. Nakhl , Thomas Quella , Martin Sevior , Muhammad Usman

We show that any $n$-qubit Clifford unitary can be implemented using at most $2n$ multi-qubit joint measurements. All the multi-qubit joint measurements used for implementing the Clifford unitary can be chosen to form at most two sets of…

Quantum Physics · Physics 2026-03-27 Vadym Kliuchnikov , Marcus P. da Silva

Quantum computing has potential to provide exponential speedups over classical computing for many important applications. However, today's quantum computers are in their early stages, and hardware quality issues hinder the scale of program…

Strongly simulating a quantum circuit, that is, computing an output amplitude, amounts to summing the circuit's Feynman paths, a weighted count over assignments to the Boolean ``path'' variables. The circuit's gates induce correlations…

Quantum computers hold unprecedented potentials for machine learning applications. Here, we prove that physical quantum circuits are PAC (probably approximately correct) learnable on a quantum computer via empirical risk minimization: to…

Quantum Physics · Physics 2022-01-04 Haoyuan Cai , Qi Ye , Dong-Ling Deng

Gate-teleportation circuits are arguably among the most basic examples of computations believed to provide a quantum computational advantage: In seminal work [Quantum Inf. Comput., 4(2):134--145], Terhal and DiVincenzo have shown that these…

Quantum Physics · Physics 2024-12-06 Libor Caha , Xavier Coiteux-Roy , Robert Koenig

We propose a new framework of topological complexity to study the computational complexity of quantum circuits and tensor networks. Within this framework, we establish the Quon Classical Simulation (QCS) for hybrid Clifford-Matchgate…

Quantum Physics · Physics 2025-08-11 Zixuan Feng , Zhengwei Liu , Fan Lu , Ningfeng Wang

Generating samples from the output distribution of a quantum circuit is a ubiquitous task used as a building block of many quantum algorithms. Here we show how to accomplish this task on a noisy quantum processor lacking full-blown error…

Clifford algebras are used for definition of spinors. Because of using spin-1/2 systems as an adequate model of quantum bit, a relation of the algebras with quantum information science has physical reasons. But there are simple mathematical…

Quantum Physics · Physics 2007-05-23 Alexander Yu. Vlasov

We present an algorithm that decomposes any $n$-qubit Clifford operator into a circuit consisting of three subcircuits containing only CNOT or CPHASE gates with layers of one-qubit gates before and after each of these subcircuits. As with…

Quantum Physics · Physics 2023-10-18 Timothy Proctor , Kevin Young

We investigate quantum circuits built from arbitrary single-qubit operations combined with programmable all-to-all multiqubit entangling gates that are native to, among other systems, trapped-ion quantum computing platforms. We report a…

Quantum Physics · Physics 2025-10-16 Jonathan Nemirovsky , Lee Peleg , Amit Ben Kish , Yotam Shapira

The Clifford Hierarchy has been a central topic in quantum computation due to its strong connections with fault-tolerant quantum computation, magic state distillation, and more. Nevertheless, only sections of the hierarchy are fully…

Quantum Physics · Physics 2026-03-13 Luca Bastioni , Samuel Glandon , Tefjol Pllaha , Madison Stewart , Phillip Waitkevich

IBM has made several quantum computers available to researchers around the world via cloud services. Two architectures with five qubits, one with 16, and one with 20 qubits are available to run experiments. The IBM architectures implement…

Emerging Technologies · Computer Science 2022-06-10 Gerhard W. Dueck , Anirban Pathak , Md Mazder Rahman , Abhishek Shukla , Anindita Banerjee

It is known that the matrices that can be exactly represented by a multiqubit circuit over the Toffoli+Hadamard, Clifford+$T$, or, more generally, Clifford-cyclotomic gate set are precisely the unitary matrices with entries in the ring…

Quantum Physics · Physics 2024-08-13 Andrew N. Glaudell , Neil J. Ross , John van de Wetering , Lia Yeh