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Matchgates are a restricted set of two-qubit gates known to be classically simulable under particular conditions. Specifically, if a circuit consists only of nearest-neighbour matchgates, an efficient classical simulation is possible if…

Quantum Physics · Physics 2016-06-24 Daniel J. Brod

Quantum computers have the potential to outperform classical computers, but are currently limited in their capabilities. One such limitation is the restricted connectivity between qubits, as captured by the hardware's coupling graph. This…

Quantum Physics · Physics 2023-06-09 Joris Kattemölle , Seenivasan Hariharan

We derive a universal performance limit for coherent quantum control in the presence of modeled and unmodeled uncertainties. For any target unitary $W$ that is implementable in the absence of error, we prove that the worst-case (and hence…

Quantum Physics · Physics 2025-07-14 Robert L. Kosut , Daniel A. Lidar , Herschel Rabitz

A major challenge in practical quantum computation is the ineludible errors caused by the interaction of quantum systems with their environment. Fault-tolerant schemes, in which logical qubits are encoded by several physical qubits, enable…

Quantum Physics · Physics 2020-12-17 Kai Sun , Jin-Shi Xu , Xiao-Ye Xu , Yong-Jian Han , Chuan-Feng Li , Guang-Can Guo

A key requirement for scalable quantum computing is that elementary quantum gates can be implemented with sufficiently low error. One method for determining the error behavior of a gate implementation is to perform process tomography.…

Quantum computers process information with the laws of quantum mechanics. Current quantum hardware is noisy, can only store information for a short time, and is limited to a few quantum bits, i.e., qubits, typically arranged in a planar…

The problem of reliably certifying the outcome of a computation performed by a quantum device is rapidly gaining relevance. We present two protocols for a classical verifier to verifiably delegate a quantum computation to two…

Quantum Physics · Physics 2020-01-13 Andrea Coladangelo , Alex Grilo , Stacey Jeffery , Thomas Vidick

The identification of an unknown quantum gate is a significant issue in quantum technology. In this paper, we propose a quantum gate identification method within the framework of quantum process tomography. In this method, a series of pure…

Quantum Physics · Physics 2019-05-15 Yuanlong Wang , Qi Yin , Daoyi Dong , Bo Qi , Ian R. Petersen , Zhibo Hou , Hidehiro Yonezawa , Guo-Yong Xiang

Demonstrating quantum advantage requires experimental implementation of a computational task that is hard to achieve using state-of-the-art classical systems. One approach is to perform sampling from a probability distribution associated…

Quantum Physics · Physics 2024-05-03 Xun Gao , Marcin Kalinowski , Chi-Ning Chou , Mikhail D. Lukin , Boaz Barak , Soonwon Choi

In this note we describe a simple and intriguing observation: the quantum Fourier transform (QFT) over $Z_q$, which is considered the most ``quantum'' part of Shor's algorithm, can in fact be simulated efficiently by classical computers.…

Quantum Physics · Physics 2007-05-23 Dorit Aharonov , Zeph Landau , Johann Makowsky

We study a general family of quantum protocols for position verification and present a new class of attacks based on the Clifford hierarchy. These attacks outperform current strategies based on port-based teleportation for a large class of…

Quantum Physics · Physics 2015-11-06 Kaushik Chakraborty , Anthony Leverrier

Demonstrating quantum advantage in machine learning tasks requires navigating a complex landscape of proposed models and algorithms. To bring clarity to this search, we introduce a framework that connects the structure of parametrized…

Quantum Physics · Physics 2025-12-23 Sergi Masot-Llima , Elies Gil-Fuster , Carlos Bravo-Prieto , Jens Eisert , Tommaso Guaita

We define a model of quantum computation with local fermionic modes (LFMs) -- sites which can be either empty or occupied by a fermion. With the standard correspondence between the Foch space of $m$ LFMs and the Hilbert space of $m$ qubits,…

Quantum Physics · Physics 2009-11-06 Sergey Bravyi , Alexei Kitaev

We consider recent works on the simulation of quantum circuits using the formalism of matrix product states and the formalism of contracting tensor networks. We provide simplified direct proofs of many of these results, extending an…

Quantum Physics · Physics 2007-05-23 Richard Jozsa

Fault-tolerant quantum computing requires gates which function correctly despite the presence of errors, and are scalable if the error probability-per-gate is below a threshold value. To date, no method has been described for calculating…

Control barrier functions are a popular method of ensuring system safety, and these functions can be used to enforce invariance of a set under the dynamics of a system. A control barrier function must have certain properties, and one must…

Systems and Control · Electrical Eng. & Systems 2022-12-02 Ellie Pond , Matthew Hale

We give a new theoretical solution to a leading-edge experimental challenge, namely to the verification of quantum computations in the regime of high computational complexity. Our results are given in the language of quantum interactive…

Quantum Physics · Physics 2018-06-25 Anne Broadbent

A proof of quantumness is a type of challenge-response protocol in which a classical verifier can efficiently certify the quantum advantage of an untrusted prover. That is, a quantum prover can correctly answer the verifier's challenges and…

Quantum Physics · Physics 2022-09-21 Zhenning Liu , Alexandru Gheorghiu

Today, people are looking forward to get an awesome computational power. This kind of desire can be answered by quantum computing. By adopting quantum mechanics theory, it can generate a very fast computation result. As known, quantum…

Other Computer Science · Computer Science 2015-12-18 A. B. Mutiara , R. Refianti , J. S. K. Karamoy

Quantum Merlin-Arthur proof systems are believed to be stronger than both their classical counterparts and ``stand-alone'' quantum computers when Arthur is assumed to operate in $\Omega(\log n)$ space. No hint of such an advantage over…

Computational Complexity · Computer Science 2025-05-14 A. C. Cem Say