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We improve the number of $T$ gates needed for a $b$-bit approximation of a multiplexed quantum gate with $c$ controls applying $n$ single-qubit arbitrary phase rotations from $4n b+\mathcal{O}(\sqrt{cn b})$ to $2n b+\mathcal{O}(\sqrt{cn…

Quantum Physics · Physics 2021-10-27 Guang Hao Low

With recent advancements in quantum computing technology, optimizing quantum circuits and ensuring reliable quantum state preparation have become increasingly vital. Traditional methods often demand extensive expertise and manual…

As quantum computers improve in the number of qubits and fidelity, the question of when they surpass state-of-the-art classical computation for a well-defined computational task is attracting much attention. The leading candidate task for…

Quantum Physics · Physics 2021-01-05 Igor L. Markov , Aneeqa Fatima , Sergei V. Isakov , Sergio Boixo

Due to the unreliability and limited capacity of existing quantum computer prototypes, quantum circuit simulation continues to be a vital tool for validating next generation quantum computers and for studying variational quantum algorithms,…

Quantum Physics · Physics 2021-04-01 Yipeng Huang , Steven Holtzen , Todd Millstein , Guy Van den Broeck , Margaret Martonosi

We study two-qubit circuits over the Clifford+CS gate set, which consists of the Clifford gates together with the controlled-phase gate CS=diag(1,1,1,i). The Clifford+CS gate set is universal for quantum computation and its elements can be…

Quantum Physics · Physics 2021-06-21 Andrew N. Glaudell , Neil J. Ross , Jacob M. Taylor

We introduce a general framework for weak transversal gates -- probabilistic implementation of logical unitaries realized by local physical unitaries -- and propose a novel partially fault-tolerant quantum computing architecture that…

Quantum Physics · Physics 2025-10-10 Nobuyuki Yoshioka , Alireza Seif , Andrew Cross , Ali Javadi-Abhari

We study how much noise can be tolerated by a universal gate set before it loses its quantum-computational power. Specifically we look at circuits with perfect stabilizer operations in addition to imperfect non-stabilizer gates. We prove…

Quantum Physics · Physics 2009-12-24 Wim van Dam , Mark Howard

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

Randomized benchmarking is a widely used experimental technique to characterize the average error of quantum operations. Benchmarking procedures that scale to enable characterization of $n$-qubit circuits rely on efficient procedures for…

Quantum Physics · Physics 2016-05-20 Andrew W. Cross , Easwar Magesan , Lev S. Bishop , John A. Smolin , Jay M. Gambetta

We prove new lower bounds on the growth of robust quantum circuit complexity -- the minimal number of gates $C_{\delta}(U)$ to approximate a unitary $U$ up to an error of $\delta$ in operator norm distance. More precisely we show two bounds…

Quantum Physics · Physics 2023-06-05 Jonas Haferkamp

Fault tolerance is widely regarded as indispensable for achieving scalable and reliable quantum computing. However, the spacetime overhead required for fault-tolerant quantum computating remains prohibitively large. A critical challenge…

Quantum Physics · Physics 2025-11-26 Pei Zeng , Guo Zheng , Qian Xu , Liang Jiang

In order to evaluate, validate, and refine the design of new quantum algorithms or quantum computers, researchers and developers need methods to assess their correctness and fidelity. This requires the capabilities of quantum circuit…

Quantum Physics · Physics 2018-11-16 Xin-Chuan Wu , Sheng Di , Franck Cappello , Hal Finkel , Yuri Alexeev , Frederic T. Chong

We consider the problem of calculating the logical error probability for a stabilizer quantum code subject to random Pauli errors. To access the regime of large code distances where logical errors are extremely unlikely we adopt the…

Quantum Physics · Physics 2013-12-19 Sergey Bravyi , Alexander Vargo

Fault-tolerant quantum computation requires minimizing non-Clifford gates, whose implementation via magic state distillation dominates the resource costs. While $T$-count minimization is well-studied, dedicated $CCZ$ factories shift the…

Quantum Physics · Physics 2026-02-18 Kirill Khoruzhii , Patrick Gelß , Sebastian Pokutta

Optimization of circuits is an essential task for both quantum and classical computers to improve their efficiency. In contrast, classical logic optimization is known to be difficult, and a lot of heuristic approaches have been developed so…

Quantum Physics · Physics 2025-05-14 Yusei Mori , Hideaki Hakoshima , Kyohei Sudo , Toshio Mori , Kosuke Mitarai , Keisuke Fujii

The success probability of a quantum algorithm constructed from noisy quantum gates cannot be accurately predicted from single parameter metrics that compare noisy and ideal gates. We illustrate this concept by examining a system with…

Quantum Physics · Physics 2019-03-27 Daniel C. Murphy , Kenneth R. Brown

Gate set tomography (GST) is a self-consistent and highly accurate method for the tomographic reconstruction of a quantum information processor's quantum logic operations, including gates, state preparations, and measurements. However,…

Error mitigation is essential for near-term quantum devices, and two promising techniques are universal frame randomization and Randomized Compilation. These methods insert random twirling gates into a circuit to reduce errors while…

Quantum Physics · Physics 2025-11-04 Rachel E. Johnson , Joshua A. Job , Steve Adachi

We consider the hardness of computing additive approximations to output probabilities of random quantum circuits. We consider three random circuit families, namely, Haar random, $p=1$ QAOA, and random IQP circuits. Our results are as…

Quantum Physics · Physics 2022-06-14 Hari Krovi

We introduce a measure for evaluating the efficiency of finite universal quantum gate sets $\mathcal{S}$, called the Quantum Circuit Overhead (QCO), and the related notion of $T$-Quantum Circuit Overhead ($T$-QCO). QCO compares the circuit…

Quantum Physics · Physics 2026-05-21 Oskar Słowik , Piotr Dulian , Adam Sawicki