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Noise in existing quantum processors only enables an approximation to ideal quantum computation. However, these approximations can be vastly improved by error mitigation, for the computation of expectation values, as shown by small-scale…

Noisy intermediate-scale quantum (NISQ) devices pave the way to implement quantum algorithms that exhibit supremacy over their classical counterparts. Due to the intrinsic noise and decoherence in the physical system, NISQ computations are…

Quantum Physics · Physics 2025-09-12 Entong He , Yuxiang Yang

$\mathsf{QAC}^0$ is the class of constant-depth polynomial-size quantum circuits constructed from arbitrary single-qubit gates and generalized Toffoli gates. It is arguably the smallest natural class of constant-depth quantum computation…

Computational Complexity · Computer Science 2026-01-07 Daniel Grier , Jackson Morris , Kewen Wu

We present a constructive method to create quantum circuits that implement oracles $|x\rangle|y\rangle|0\rangle^k \mapsto |x\rangle|y \oplus f(x)\rangle|0\rangle^k$ for $n$-variable Boolean functions $f$ with low $T$-count. In our method…

Quantum Physics · Physics 2019-08-06 Giulia Meuli , Mathias Soeken , Earl Campbell , Martin Roetteler , Giovanni De Micheli

There is no unique way to encode a quantum algorithm into a quantum circuit. With limited qubit counts, connectivities, and coherence times, circuit optimization is essential to make the best use of near-term quantum devices. We introduce…

Quantum circuits must run on quantum computers with tight limits on qubit and gate counts. To generate circuits respecting both limits, a promising opportunity is exploiting uncomputation to trade qubits for gates. We present Reqomp, a…

Quantum Physics · Physics 2024-02-21 Anouk Paradis , Benjamin Bichsel , Martin Vechev

We present a scalable set of universal gates and multiply controlled gates in a qudit basis through a bijective mapping from N qubits to qudits with D = 2^N levels via rotations in U(2). For each of the universal gates (H, CNOT, and T), as…

Quantum Physics · Physics 2022-06-16 Pamela Rambow , Mingzhen Tian

We present the design of a quantum carry-lookahead adder using measurement-based quantum computation. QCLA utilizes MBQC`s ability to transfer quantum states in unit time to accelerate addition. The quantum carry-lookahead adder (QCLA) is…

Quantum Physics · Physics 2009-03-04 Agung Trisetyarso , Rodney Van Meter , Kohei M. Itoh

Hamiltonian simulation is a key quantum algorithm for modeling complex systems. To implement a Hamiltonian simulation, it is typically decomposed into a list of Pauli strings, each corresponds to an RZ rotation gate with many Clifford…

Quantum Physics · Physics 2025-10-16 Yingheng Li , Xulong Tang , Paul Hovland , Ji Liu

Quantum Random Walks, which have drawn much attention over the past few decades for their distinctly non-classical behavior, is a promising subfield within Quantum Computing. Theoretical framework and applications for these walks have seen…

Quantum Physics · Physics 2021-01-25 Daniel Koch , Michael Samodurov , Andrew Projansky , Paul M. Alsing

The study of the boundary between classically simulable and computationally complex quantum dynamics is fundamental to understanding which physical resources may enable enhanced information-processing capabilities. We investigate this…

Quantum Physics · Physics 2026-05-08 Moein N. Ivaki , Matias Karjula , Tapio Ala-Nissila

We introduce new rounding methods to improve the accuracy of finite precision quantum arithmetic. These quantum rounding methods are applicable when multiple samples are being taken from a quantum program. We show how to use multiple…

Quantum Physics · Physics 2021-08-18 Rajiv Krishnakumar , William Zeng

Existing quantum systems provide very limited physical qubit counts, trying to execute a quantum algorithm/circuit on them that have a higher number of logical qubits than physically available lead to a compile-time error. Given that it is…

Emerging Technologies · Computer Science 2023-01-03 Movahhed Sadeghi , Soheil Khadirsharbiyani , Mahmut Taylan Kandemir

Topological quantum computing promises intrinsic fault tolerance by encoding quantum information in non-Abelian anyons, where quantum gates are implemented via braiding. While braiding operations are robust against local perturbations, a…

Quantum Physics · Physics 2025-08-15 Themba Hodge , Philipp Frey , Stephan Rachel

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

The work proposes an extension of the quantum circuit formalism where qubits (wires) are circular instead of linear. The left-to-right interpretation of a quantum circuit is replaced by a circular representation which allows to select the…

Quantum Physics · Physics 2016-04-12 Alexandru Paler

Efficient arithmetic operations are a prerequisite for practical quantum computing. Optimization efforts focus on two primary metrics: Quantum Cost (QC), determined by the number of non-linear gates, and Logical Depth, which defines the…

Quantum Physics · Physics 2025-12-17 G. Papakonstantinou

We present the design of a quantum carry-lookahead adder using measurement-based quantum computation. The quantum carry-lookahead adder (QCLA) is faster than a quantum ripple-carry adder; QCLA has logarithmic depth while ripple adders have…

Quantum Physics · Physics 2009-01-27 Agung Trisetyarso , Rodney Van Meter , Kohei M. Itoh

The current phase of quantum computing is in the Noisy Intermediate-Scale Quantum (NISQ) era. On NISQ devices, two-qubit gates such as CNOTs are much noisier than single-qubit gates, so it is essential to minimize their count. Quantum…

Quantum Physics · Physics 2022-03-24 Xin-Chuan Wu , Marc Grau Davis , Frederic T. Chong , Costin Iancu

We examine the detailed scenario for implementing n-control-qubit Toffoli gates and select gates on ion-trap quantum computers, especially those that shuttle ions into interaction zones. We determine expected performance of these gates with…

Quantum Physics · Physics 2021-03-02 Nilesh Goel , J. K. Freericks