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Unitary decomposition is a widely used method to map quantum algorithms to an arbitrary set of quantum gates. Efficient implementation of this decomposition allows for translation of bigger unitary gates into elementary quantum operations,…

Quantum Physics · Physics 2024-03-14 A. M. Krol , A. Sarkar , I. Ashraf , Z. Al-Ars , K. Bertels

We present an algorithm for the approximate decomposition of diagonal operators, focusing specifically on decompositions over the Clifford+$T$ basis, that minimize the number of phase-rotation gates in the synthesized approximation circuit.…

Quantum Physics · Physics 2016-06-13 Jonathan Welch , Alex Bocharov , Krysta M. Svore

We show the applicability of the Cartan decomposition of Lie algebras to quantum circuits. This approach can be used to synthesize circuits that can efficiently implement any desired unitary operation. Our method finds explicit quantum…

Quantum circuits of a general quantum gate acting on multiple $d$-level quantum systems play a prominent role in multi-valued quantum computation. We first propose a new recursive Cartan decomposition of semi-simple unitary Lie group…

Quantum Physics · Physics 2024-05-29 Gui-Long Jiang , Wen-Qiang Liu , Hai-Rui Wei

A critical step in developing circuits for quantum simulation is to synthesize a desired unitary operator using the circuit building blocks. Studying unitaries and their generators from the Lie algebraic perspective has given rise to…

Quantum Physics · Physics 2025-12-09 Omar Alsheikh , Efekan Kökcü , Bojko N. Bakalov , A. F. Kemper

In this work, we report on a novel quantum gate approximation algorithm based on the application of parametric two-qubit gates in the synthesis process. The utilization of these parametric two-qubit gates in the circuit design allows us to…

Quantum Physics · Physics 2022-11-16 Péter Rakyta , Zoltán Zimborás

Resource-efficient and high-precision approximate synthesis of quantum circuits expressed in the Clifford+T gate set is vital for Fault-Tolerant quantum computing. Efficient optimal methods are known for single-qubit RZ unitaries, otherwise…

Quantum Physics · Physics 2026-04-27 Mathias Weiden , Justin Kalloor , John Kubiatowicz , Ed Younis , Costin Iancu

A flag is a sequence of nested subspaces. Flags are ubiquitous in numerical analysis, arising in finite elements, multigrid, spectral, and pseudospectral methods for numerical PDE; they arise in the form of Krylov subspaces in matrix…

Optimization and Control · Mathematics 2019-08-08 Ke Ye , Ken Sze-Wai Wong , Lek-Heng Lim

During the noisy intermediate-scale quantum (NISQ) era, it is important to optimize the quantum circuits in circuit depth and gate count, especially entanglement gates, including the CNOT gate. Among all the unitary operators, diagonal…

Quantum Physics · Physics 2024-04-15 Xinchi Huang , Taichi Kosugi , Hirofumi Nishi , Yu-ichiro Matsushita

Quantum unitary synthesis addresses the problem of translating abstract quantum algorithms into sequences of hardware-executable quantum gates. Solving this task exactly is infeasible in general due to the exponential growth of the…

Quantum Physics · Physics 2026-02-19 Lukas Theißinger , Thore Gerlach , David Berghaus , Christian Bauckhage

Decoupling systems into independently evolving components has a long history of simplifying seemingly complex systems. They enable a better understanding of the underlying dynamics and causal structures while providing more efficient means…

Quantum Physics · Physics 2024-06-11 Ximing Wang , Chengran Yang , Mile Gu

We introduce a novel parameterization of complex unitary matrices, which allows for the efficient photonic implementation of arbitrary linear discrete unitary operators. The proposed architecture is built on factorizing an $N \times N$…

Optics · Physics 2023-07-17 Matthew Markowitz , Mohammad-Ali Miri

Recently it has been shown that Repeat-Until-Success (RUS) circuits can approximate a given single-qubit unitary with an expected number of $T$ gates of about $1/3$ of what is required by optimal, deterministic, ancilla-free decompositions…

Quantum Physics · Physics 2015-06-11 Alex Bocharov , Martin Roetteler , Krysta M. Svore

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 operation is an essential step for quantum information processing. We first propose an iterative procedure for decomposing a general unitary operation without resorting to controlled-NOT gate and single-qubit rotation library. Based…

Quantum Physics · Physics 2022-04-06 Wen-Qiang Liu , Xin-Jie Zhou , Hai-Rui Wei

In this work we present a method of decomposition of arbitrary unitary matrix $U\in\mathbf U(2^k)$ into a product of single-qubit negator and controlled-$\sqrt{\mbox{NOT}}$ gates. Since the product results with negator matrix, which can be…

Quantum Physics · Physics 2016-10-27 Adam Glos , Przemysław Sadowski

Although only two quantum states of a physical system are often used to encode quantum information in the form of qubits, many levels can in principle be used to obtain qudits and increase the information capacity of the system. To take…

Quantum Physics · Physics 2025-06-25 Aryan Iliat , Mark Byrd , Sahel Ashhab , LianAo Wu

We consider a generic elementary gate sequence which is needed to implement a general quantum gate acting on n qubits -- a unitary transformation with 4^n degrees of freedom. For synthesizing the gate sequence, a method based on the…

Quantum Physics · Physics 2009-11-10 Mikko Mottonen , Juha J. Vartiainen , Ville Bergholm , Martti M. Salomaa

Quantum circuit synthesis is the task of decomposing a given quantum operator into a sequence of elementary quantum gates. Since the finite target gate set cannot exactly implement any given operator, approximation is often necessary. Model…

Quantum Physics · Physics 2025-11-05 Dekel Zak , Jingyi Mei , Jean-Marie Lagniez , Alfons Laarman

We present a simple algorithm that implements an arbitrary $n$-qubit unitary operator using a Clifford+T circuit with T-count $O(2^{4n/3} n^{2/3})$. This improves upon the previous best known upper bound of $O(2^{3n/2} n)$, while the best…

Quantum Physics · Physics 2025-10-01 Xinyu Tan
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