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We demonstrate a method for general linear optical networks that allows one to factorize any SU($n$) matrix in terms of two SU($n-1)$ blocks coupled by an SU(2) entangling beam splitter. The process can be recursively continued in an…

Quantum Physics · Physics 2018-03-07 Hubert de Guise , Olivia Di Matteo , Luis L. Sanchez-Soto

A general scheme is presented to decompose a $d$-by-$d$ unitary matrix as the product of two-level unitary matrices with additional structure and prescribed determinants. In particular, the decomposition can be done by using two-level…

Quantum Physics · Physics 2013-03-11 Chi-Kwong Li , Rebecca Roberts , Xiaoyan Yin

In this work, we develop a novel mathematical framework for universal digital quantum computation using algebraic probability theory. We rigorously define quantum circuits as finite sequences of elementary quantum gates and establish their…

Quantum Physics · Physics 2026-01-01 Antonio Falcó , Daniela Falcó--Pomares , Hermann G. Matthies

Quantum circuits currently constitute a dominant model for quantum computation. Our work addresses the problem of constructing quantum circuits to implement an arbitrary given quantum computation, in the special case of two qubits. We…

Quantum Physics · Physics 2009-11-07 Stephen S. Bullock , Igor L. Markov

We numerically investigate the statement that local random quantum circuits acting on n qubits composed of polynomially many nearest neighbour two-qubit gates form an approximate unitary poly(n)-design [F.G.S.L. Brandao et al.,…

We consider the problem of deciding if a set of quantum one-qudit gates $\mathcal{S}=\{U_1,\ldots,U_n\}$ is universal. We provide the compact form criteria leading to a simple algorithm that allows deciding universality of any given set of…

Quantum Physics · Physics 2017-06-09 Adam Sawicki , Katarzyna Karnas

Multi-controlled unitary gates have been a subject of interest in quantum computing since its inception, and are widely used in quantum algorithms. The current state-of-the-art approach to implementing n-qubit multi-controlled gates…

Near-term quantum computers are primarily limited by errors in quantum operations (or gates) between two quantum bits (or qubits). A physical machine typically provides a set of basis gates that include primitive 2-qubit (2Q) and 1-qubit…

Nielsen [quant-ph/0108020] showed that universal quantum computation is possible given quantum memory and the ability to perform projective measurements on up to 4-qubits. We describe an improved method that requires only 2-qubit…

Quantum Physics · Physics 2007-05-23 D. W. Leung

We introduce the first complete equational theory for quantum circuits. More precisely, we introduce a set of circuit equations that we prove to be sound and complete: two circuits represent the same unitary map if and only if they can be…

Quantum Physics · Physics 2023-11-15 Alexandre Clément , Nicolas Heurtel , Shane Mansfield , Simon Perdrix , Benoît Valiron

Quantum algorithms require a universal set of gates that can be implemented in a physical system. For these, an optimal decomposition into a sequence of available operations is desired. Here, we present a method to find such sequences for a…

Quantum Physics · Physics 2016-07-22 Esteban A. Martinez , Thomas Monz , Daniel Nigg , Philipp Schindler , Rainer Blatt

We study the implementation of a universal quantum gate set via multiple-braiding within $SU(2)_k$ ($k > 2$, $k \neq 4$) anyon models. The multiple elementary braiding matrices (MEBMs) are derived from the $q$-deformed representation theory…

Quantum Physics · Physics 2026-04-23 Jiangwei Long , Zihui Liu , Yizhi Li , Jianxin Zhong , Lijun Meng

Unitary synthesis is the process of decomposing a target unitary transformation into a sequence of quantum gates. This is a challenging task, as the number of possible gate combinations grows exponentially with the circuit depth. In this…

Quantum Physics · Physics 2025-09-01 Xavier Valcarce , Bastien Grivet , Nicolas Sangouard

Unitary $T$-designs play an important role in quantum information, with diverse applications in quantum algorithms, benchmarking, tomography, and communication. Until now, the most efficient construction of unitary $T$-designs for $n$-qudit…

Quantum Physics · Physics 2025-02-18 Chi-Fang Chen , Jordan Docter , Michelle Xu , Adam Bouland , Patrick Hayden

In recent years, parameterized quantum circuits have become a major tool to design quantum algorithms for optimization problems. The challenge in fully taking advantage of a given family of parameterized circuits lies in finding a good set…

Quantum Physics · Physics 2022-09-05 Eunou Lee

Although quantum computers have the potential to efficiently solve certain problems considered difficult by known classical approaches, the design of a quantum circuit remains computationally difficult. It is known that the optimal gate…

Optimization and Control · Mathematics 2010-12-06 Srinivas Sridharan , Mile Gu , Matthew R. James , William M. McEneaney

Many promising quantum algorithms in economics, medical science, and material science rely on circuits that are parameterized by a large number of angles. To ensure that these algorithms are efficient, these parameterized circuits must be…

Quantum Physics · Physics 2025-07-09 Neil J. Ross , Scott Wesley

Current quantum devices have unutilized high-level quantum resources. More and more attention has been paid to the qudit quantum systems with larger than two dimensions to maximize the potential computing power of quantum computation. Then,…

Quantum Physics · Physics 2025-04-18 Shuai Yang , Lihao Xu , Guojing Tian , Xiaoming Sun

Optimizing the size and depth of CNOT circuits is an active area of research in quantum computing and is particularly relevant for circuits synthesized from the Clifford + T universal gate set. Although many techniques exist for finding…

Quantum Physics · Physics 2025-07-15 Alan Bu , Evan Fan , Robert Sanghyeon Joo

We define and construct efficient depth-universal and almost-size-universal quantum circuits. Such circuits can be viewed as general-purpose simulators for central classes of quantum circuits and can be used to capture the computational…

Computational Complexity · Computer Science 2008-04-16 Debajyoti Bera , Stephen Fenner , Frederic Green , Steve Homer