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Prior work of Beverland et al. has shown that any exact Clifford+$T$ implementation of the $n$-qubit Toffoli gate must use at least $n$ $T$ gates. Here we show how to get away with exponentially fewer $T$ gates, at the cost of incurring a…

Quantum Physics · Physics 2025-10-09 David Gosset , Robin Kothari , Chenyi Zhang

Various quantum algorithms require usage of arbitrary diagonal operators as subroutines. For their execution on a physical hardware, those operators must be first decomposed into target device's native gateset and its qubit connectivity for…

Quantum Physics · Physics 2024-03-05 Jan Tułowiecki , Łukasz Czerwiński , Konrad Deka , Jan Gwinner , Witold Jarnicki , Adam Szady

In this paper we study the potential of using reinforcement learning (RL) in order to synthesize quantum circuits, while optimizing the T-count and CS-count, of unitaries that are exactly implementable by the Clifford+T and Clifford+CS gate…

Quantum Physics · Physics 2025-12-12 David Kremer , Ali Javadi-Abhari , Priyanka Mukhopadhyay

We develop a method to synthesize a class of entangling multi-qubit gates for a quantum computing platform with fixed Ising-type interaction with all-to-all connectivity. The only requirement on the flexibility of the interaction is that it…

Before executing a quantum algorithm, one must first decompose the algorithm into machine-level instructions compatible with the architecture of the quantum computer, a process known as quantum compiling. There are many different quantum…

Quantum Physics · Physics 2018-06-08 Luke Heyfron , Earl T. Campbell

Clifford circuit optimization is an important step in the quantum compilation pipeline. Major compilers employ heuristic approaches. While they are fast, their results are often suboptimal. Minimization of noisy gates, like 2-qubit CNOT…

Quantum Physics · Physics 2025-04-02 Irfansha Shaik , Jaco van de Pol

We show how to directly and efficiently approximate arbitrary one-qubit unitaries, bypassing the Euler decomposition and the magnitude approximation problem, at the cost of one ancillary qubit. Our technique also applies to approximating…

Quantum Physics · Physics 2026-04-23 Vadym Kliuchnikov , Jendrik Brachter , Marcus P. da Silva

Metaplectic quantum basis is a universal multi-qutrit quantum basis, formed by the ternary Clifford group and the axial reflection gate $R=|0\rangle \langle 0| + |1\rangle \langle 1| - |2\rangle \langle 2|$. It is arguably, a ternary basis…

Quantum Physics · Physics 2018-01-22 Alex Bocharov

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

Hamiltonian simulation represents an important module in a large class of quantum algorithms and simulations such as quantum machine learning, quantum linear algebra methods, and modeling for physics, material science and chemistry. One of…

Quantum Physics · Physics 2023-05-30 Albert T. Schmitz , Nicolas P. D. Sawaya , Sonika Johri , A. Y. Matsuura

Unitary and non-unitary diagonal operators are fundamental building blocks in quantum algorithms with applications in the resolution of partial differential equations, Hamiltonian simulations, the loading of classical data on quantum…

Quantum Physics · Physics 2025-01-22 Julien Zylberman , Ugo Nzongani , Andrea Simonetto , Fabrice Debbasch

Efficient synthesis of arbitrary quantum states and unitaries from a universal fault-tolerant gate-set e.g. Clifford+T is a key subroutine in quantum computation. As large quantum algorithms feature many qubits that encode coherent quantum…

Quantum Physics · Physics 2024-06-19 Guang Hao Low , Vadym Kliuchnikov , Luke Schaeffer

As quantum processors grow in scale and reliability, the need for efficient quantum gate decomposition of circuits to a set of specific available gates, becomes ever more critical. The decomposition of a particular algorithm into a sequence…

Quantum Physics · Physics 2025-01-30 Jonathan Nemirovsky , Maya Chuchem , Yotam Shapira

Current noisy intermediate-scale quantum (NISQ) devices can only execute small circuits with shallow depth, as they are still constrained by the presence of noise: quantum gates have error rates and quantum states are fragile due to…

Quantum Physics · Physics 2024-06-11 Shihao Zhang , Kai Huang , Lvzhou Li

Clifford gates play a role in the optimisation of Clifford+T circuits. Reducing the count and the depth of Clifford gates, as well as the optimal scheduling of T gates, influence the hardware and the time costs of executing quantum…

Quantum Physics · Physics 2019-06-18 Alexandru Paler , Robert Basmadjian

We consider the problem of approximating arbitrary single-qubit z-rotations by ancilla-free Clifford+T circuits, up to given epsilon. We present a fast new probabilistic algorithm for solving this problem optimally, i.e., for finding the…

Quantum Physics · Physics 2018-04-17 Neil J. Ross , Peter Selinger

Classical simulation of quantum circuits plays a crucial role in validating quantum hardware and delineating the boundaries of quantum advantage. Among the most effective simulation techniques are those based on the stabilizer extent, which…

Quantum Physics · Physics 2025-10-23 Giulio Camillo , Filipa C. R. Peres , Markus Heinrich , Juani Bermejo-Vega

We present a decomposition technique that uses non-deterministic circuits to approximate an arbitrary single-qubit unitary to within distance $\epsilon$ and requires significantly fewer non-Clifford gates than existing techniques. We…

Quantum Physics · Physics 2014-10-21 Adam Paetznick , Krysta M. Svore

We consider quantum circuits composed of Clifford and T gates. In this context the T gate has a special status since it confers universal computation when added to the (classically simulable) Clifford gates. However it can be very expensive…

Quantum Physics · Physics 2013-08-21 David Gosset , Vadym Kliuchnikov , Michele Mosca , Vincent Russo

Prevailing proposals for the first generation of quantum computers make use of 2-level systems, or qubits, as the fundamental unit of quantum information. However, recent innovations in quantum error correction and magic state distillation…

Quantum Physics · Physics 2019-02-18 Luke E. Heyfron , Earl Campbell