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We present a quantum algorithm for multiplying two $n$-bit integers with overall circuit depth and $T$-depth both bounded by $O(\log^{2} n)$, while using $O(n^{2})$ gates and ancillary qubits. Our construction generates partial products via…

Quantum Physics · Physics 2026-04-14 Fred Sun , Anton Borissov

Among the cost metrics characterizing a quantum circuit, the $T$-count stands out as one of the most crucial as its minimization is particularly important in various areas of quantum computation such as fault-tolerant quantum computing and…

Quantum Physics · Physics 2025-09-17 Vivien Vandaele

Estimating expectation values on near-term quantum computers often requires a prohibitively large number of measurements. One widely-used strategy to mitigate this problem has been to partition an operator's Pauli terms into sets of…

Magic state distillation and the Shor factoring algorithm make essential use of logical diagonal gates. We introduce a method of synthesizing CSS codes that realize a target logical diagonal gate at some level $l$ in the Clifford hierarchy.…

Quantum Physics · Physics 2021-10-28 Jingzhen Hu , Qingzhong Liang , Robert Calderbank

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

Compiling quantum circuits to account for hardware restrictions is an essential part of the quantum computing stack. Circuit compilation allows us to adapt algorithm descriptions into a sequence of operations supported by real quantum…

Quantum Physics · Physics 2025-10-14 Alejandro Villoria , Henning Basold , Alfons Laarman

Algorithms for numerical tasks in finite precision simultaneously seek to minimize the number of floating point operations performed, and also the number of bits of precision required by each floating point operation. This paper presents an…

Numerical Analysis · Mathematics 2024-08-20 Rikhav Shah

Quantum error-correcting codes can be used to protect qubits involved in quantum computation. This requires that logical operators acting on protected qubits be translated to physical operators (circuits) acting on physical quantum states.…

Information Theory · Computer Science 2021-08-20 Narayanan Rengaswamy , Robert Calderbank , Swanand Kadhe , Henry D. Pfister

Stabilizer codes are a simple and successful class of quantum error-correcting codes. Yet this success comes in spite of some harsh limitations on the ability of these codes to fault-tolerantly compute. Here we introduce a new metric for…

Quantum Physics · Physics 2018-05-30 Tomas Jochym-O'Connor , Aleksander Kubica , Theodore J. Yoder

It is known that the matrices that can be exactly represented by a multiqubit circuit over the Toffoli+Hadamard, Clifford+$T$, or, more generally, Clifford-cyclotomic gate set are precisely the unitary matrices with entries in the ring…

Quantum Physics · Physics 2024-08-13 Andrew N. Glaudell , Neil J. Ross , John van de Wetering , Lia Yeh

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

Since an n-qubit circuit consisting of CNOT gates can have up to $\Omega(n^2/\log{n})$ CNOT gates, it is natural to expect that $\Omega(n^2/\log{n})$ Toffoli gates are needed to apply a controlled version of such a circuit. We show that the…

Quantum Physics · Physics 2026-01-01 Isaac H. Kim , Tuomas Laakkonen

A central building block of many quantum algorithms is the diagonalization of Pauli operators. Although it is always possible to construct a quantum circuit that simultaneously diagonalizes a given set of commuting Pauli operators, only…

The $n$-qubit $k$-weight Dicke states $|D^n_k\rangle$, defined as the uniform superposition of all computational basis states with exactly $k$ qubits in state $|1\rangle$, form a basis of the symmetric subspace and represent an important…

Quantum Physics · Physics 2025-05-22 Pei Yuan , Shengyu Zhang

A decision diagram (DD) is a graph-like data structure for homomorphic compression of Boolean and pseudo-Boolean functions. Over the past decades, decision diagrams have been successfully applied to verification, linear algebra, stochastic…

Quantum Physics · Physics 2026-02-23 Arend-Jan Quist , Tim Coopmans , Alfons Laarman

In this paper we study single qutrit circuits consisting of words over the Clifford$+D$ cyclotomic gate set, where $D=\text{diag}(\pm\xi^{a},\pm\xi^{b},\pm\xi^{c})$, $\xi$ is a primitive $9$-th root of unity and $a,b,c$ are integers. We…

Quantum Physics · Physics 2025-03-05 Amolak Ratan Kalra , Michele Mosca , Dinesh Valluri

We propose a method for exact circuit synthesis using a discrete gate set, as required for fault-tolerant quantum computing. Our approach translates the problem of synthesizing a gate specified by its unitary matrix into a boolean…

Quantum Physics · Physics 2025-03-20 Élie Gouzien , Nicolas Sangouard

We introduce a quantum-inspired approximation algorithm for MaxCut based on low-depth Clifford circuits. We start by showing that the solution unitaries found by the adaptive quantum approximation optimization algorithm (ADAPT-QAOA) for the…

Quantum Physics · Physics 2024-06-25 Manuel H. Muñoz-Arias , Stefanos Kourtis , Alexandre Blais

Simulating quantum circuits classically is an important area of research in quantum information, with applications in computational complexity and validation of quantum devices. One of the state-of-the-art simulators, that of Bravyi et al,…

Quantum Physics · Physics 2019-08-07 Hammam Qassim , Joel J. Wallman , Joseph Emerson

Fault-tolerant quantum computation requires minimizing non-Clifford gates, whose implementation via magic state distillation dominates the resource costs. While $T$-count minimization is well-studied, dedicated $CCZ$ factories shift the…

Quantum Physics · Physics 2026-02-18 Kirill Khoruzhii , Patrick Gelß , Sebastian Pokutta