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We analyze the complexity of synthesizing random states and unitary operators in a multi-qudit system in two paradigms. In one case, we consider the situation in which we manipulate the system by applying a sequence of one- and two-qudit…

Quantum Physics · Physics 2026-05-11 Sahel Ashhab , Bora Basyildiz

Gate model quantum computers with too many qubits to be simulated by available classical computers are about to arrive. We present a strategy for programming these devices without error correction or compilation. This means that the number…

Quantum Physics · Physics 2017-03-21 E. Farhi , J. Goldstone , S. Gutmann , H. Neven

We developed a general framework for synthesizing target gates by using a finite set of basic gates, which is a crucial step in quantum compilation. When approximating a gate in SU($n$), a naive brute-force search requires a computational…

Quantum Physics · Physics 2025-10-10 Soichiro Yamazaki , Seiseki Akibue

Optimal control of closed quantum systems is a well studied geometrically elegant set of computational theory and techniques that have proven pivotal in the implementation and understanding of quantum computers. The design of a circuit…

Quantum Physics · Physics 2024-04-29 Johannes Aspman , Vyacheslav Kungurtsev , Jakub Marecek

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

Controlled gates are key components in various quantum algorithms. Improving on the prior work of Gosset et al., we show that, for an allowed error $\varepsilon$, $3\log_2(1/\varepsilon) + o(\log(1/\varepsilon))$ $T$ gates are sufficient to…

Quantum Physics · Physics 2026-03-17 Soichiro Yamazaki , Seiseki Akibue

A foundational assumption of quantum error correction theory is that quantum gates can be scaled to large processors without exceeding the error-threshold for fault tolerance. Two major challenges that could become fundamental roadblocks…

Implementation of high-dimensional (HD) quantum gates shows very promising perspectives for HD quantum computation. A bipartite quantum system with arbitrary dimensions $n$ and $m$ is termed a quNit-quMit. Here we propose a synthesis scheme…

Quantum Physics · Physics 2026-04-14 Gui-Long Jiang , Hai-Rui Wei

Control synthesis for continuously-parameterized families of quantum gates can enable critical advantages for mid-sized quantum computing applications in advance of fault-tolerance. We combine quantum optimal control with physics-informed…

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

All quantum systems are subject to noise from the environment or external controls. This noise is a major obstacle to the realization of quantum technology. For example, noise limits the fidelity of quantum gates. Employing optimal control…

Quantum Physics · Physics 2024-09-25 Aviv Aroch , Ronnie Kosloff , Shimshon Kallush

Efficient constructions for quantum logic are essential since quantum computation is experimentally challenging. This thesis develops quantum logic synthesis as a paradigm for reducing the resource overhead in fault-tolerant quantum…

Quantum Physics · Physics 2013-10-29 N. Cody Jones

We perform optimal-control-theory calculations to determine the minimum number of two-qubit CNOT gates needed to perform quantum state preparation and unitary operator synthesis for few-qubit systems. By considering all possible gate…

Quantum Physics · Physics 2022-08-24 Sahel Ashhab , Naoki Yamamoto , Fumiki Yoshihara , Kouichi Semba

The purpose of unitary synthesis is to find a gate sequence that optimally approximates a target unitary transformation. A new synthesis approach, called probabilistic synthesis, has been introduced, and its superiority has been…

Quantum Physics · Physics 2024-05-03 Seiseki Akibue , Go Kato , Seiichiro Tani

Quantum optimal control plays a crucial role in quantum computing by providing the interface between compiler and hardware. Solving the optimal control problem is particularly challenging for multi-qubit gates, due to the exponential growth…

Quantum Physics · Physics 2024-07-25 N. Anders Petersson , Stefanie Günther , Seung Whan Chung

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

Reducing the circuit depth of quantum circuits is a crucial bottleneck to enabling quantum technology. This depth is inversely proportional to the number of available quantum gates that have been synthesised. Moreover, quantum gate…

Quantum Physics · Physics 2022-12-15 Francesco Preti , Tommaso Calarco , Felix Motzoi

We use a random search technique to find quantum gate sequences that implement perfect quantum state preparation or unitary operator synthesis with arbitrary targets. This approach is based on the recent discovery that there is a large…

Quantum Physics · Physics 2024-10-25 Sahel Ashhab , Fumiki Yoshihara , Miwako Tsuji , Mitsuhisa Sato , Kouichi Semba

Reversible computation is gaining increasing relevance in the context of several post-CMOS technologies, the most prominent of those being Quantum computing. One of the key theoretical problem pertaining to reversible logic synthesis is the…

Emerging Technologies · Computer Science 2016-03-22 Anupam Chattopadhyay , Anubhab Baksi

In this paper, the problem of synthesizing a general Hermitian quantum gate into a set of primary quantum gates is addressed. To this end, an extended version of the Jacobi approach for calculating the eigenvalues of Hermitian matrices in…

Quantum Physics · Physics 2016-06-28 Mona Arabzadeh , Mahboobeh Houshmand , Mehdi Sedighi , Morteza Saheb Zamani