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The relevance of shallow-depth quantum circuits has recently increased, mainly due to their applicability to near-term devices. In this context, one of the main goals of quantum circuit complexity is to find problems that can be solved by…

Quantum Physics · Physics 2026-03-12 Alex Bredariol Grilo , Elham Kashefi , Damian Markham , Michael de Oliveira

Random quantum circuits are commonly viewed as hard to simulate classically. In some regimes this has been formally conjectured, and there had been no evidence against the more general possibility that for circuits with uniformly random…

$\mathsf{QAC}^0$ 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

Various algorithms have been developed to simulate quantum circuits on classical hardware. Among the most prominent are approaches based on \emph{stabilizer decompositions} and \emph{tensor network contraction}. In this work, we present a…

Quantum Physics · Physics 2026-03-09 Julien Codsi , Tuomas Laakkonen

It has been known for almost three decades that many $\mathrm{NP}$-hard optimization problems can be solved in polynomial time when restricted to structures of constant treewidth. In this work we provide the first extension of such results…

Computational Complexity · Computer Science 2016-02-09 Mateus de Oliveira Oliveira

We design a deterministic subexponential time algorithm that takes as input a multivariate polynomial $f$ computed by a constant-depth circuit over rational numbers, and outputs a list $L$ of circuits (of unbounded depth and possibly with…

Computational Complexity · Computer Science 2024-03-05 Mrinal Kumar , Varun Ramanathan , Ramprasad Saptharishi , Ben Lee Volk

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

Random quantum circuits have played a central role in establishing the computational advantages of near-term quantum computers over their conventional counterparts. Here, we use ensembles of low-depth random circuits with local connectivity…

Quantum Physics · Physics 2021-09-29 Michael J. Gullans , Stefan Krastanov , David A. Huse , Liang Jiang , Steven T. Flammia

Quantum circuit depth minimization is critical for practical applications of circuit-based quantum computation. In this work, we present a systematic procedure to decompose multiqubit controlled unitary gates, which is essential in many…

Quantum Physics · Physics 2022-10-06 Adenilton J. da Silva , Daniel K. Park

We study the class $\textrm{AC}^0$ of functions computed by constant-depth polynomial-size arithmetic circuits of unbounded fan-in addition and multiplication gates. No model-theoretic characterization for arithmetic circuit classes is…

Computational Complexity · Computer Science 2020-05-08 Anselm Haak , Heribert Vollmer

Random quantum circuits have been utilized in the contexts of quantum supremacy demonstrations, variational quantum algorithms for chemistry and machine learning, and blackhole information. The ability of random circuits to approximate any…

Quantum Physics · Physics 2023-03-23 Minzhao Liu , Junyu Liu , Yuri Alexeev , Liang Jiang

In this paper, a derandomized algorithm for sampling decoding is proposed to achieve near-optimal performance in lattice decoding. By setting a probability threshold to sample candidates, the whole sampling procedure becomes deterministic,…

Information Theory · Computer Science 2016-11-17 Zheng Wang , Shuiyin Liu , Cong Ling

Classical simulation of quantum circuits is a critical tool for validating quantum hardware and probing the boundary between classical and quantum computational power. Existing state-of-the-art methods, notably tensor network approaches,…

Quantum Physics · Physics 2025-10-09 Bin Cheng , Ziyuan Wang , Ruixuan Deng , Jianxin Chen , Zhengfeng Ji

Quantum error correction is instrumental in protecting quantum systems from noise in quantum computing and communication settings. Pauli channels can be efficiently simulated and threshold values for Pauli error rates under a variety of…

Quantum Physics · Physics 2017-04-25 Christopher Chamberland , Joel J. Wallman , Stefanie Beale , Raymond Laflamme

We introduce a classical algorithm for sampling the output of shallow, noisy random circuits on two-dimensional qubit arrays. The algorithm builds on the recently-proposed "space-evolving block decimation" (SEBD) and extends it to the case…

Quantum Physics · Physics 2023-11-16 Zihan Cheng , Matteo Ippoliti

In this work, we prove the strongest known lower bounds for QAC$^0$, allowing polynomially many gates and ancillae. Our main results show that: (1) Depth-3 QAC$^0$ circuits cannot compute PARITY, and require $\Omega(\exp(\sqrt{n}))$ gates…

Quantum Physics · Physics 2026-01-21 Malvika Raj Joshi , Avishay Tal , Francisca Vasconcelos , John Wright

Towards better understanding of gate elimination, the only method known that can prove complexity lower bounds for explicit functions against unrestricted Boolean circuits, this work contributes: (1) formalizing circuit simplifications as a…

Computational Complexity · Computer Science 2026-02-23 Marco Carmosino , Ngu Dang , Tim Jackman

In this paper we consider circuit synthesis for n-wire linear reversible circuits using the C-NOT gate library. These circuits are an important class of reversible circuits with applications to quantum computation. Previous algorithms,…

Quantum Physics · Physics 2015-04-21 K. N. Patel , I. L. Markov , J. P. Hayes

We show that sharp thresholds for Boolean functions directly imply average-case circuit lower bounds. More formally we show that any Boolean function exhibiting a sharp enough threshold at \emph{arbitrary} critical density cannot be…

Computational Complexity · Computer Science 2024-07-17 David Gamarnik , Elchanan Mossel , Ilias Zadik

QAC circuits are quantum circuits with one-qubit gates and Toffoli gates of arbitrary arity. QAC$^0$ circuits are QAC circuits of constant depth, and are quantum analogues of AC$^0$ circuits. We prove the following: $\bullet$ For all $d \ge…

Quantum Physics · Physics 2020-12-01 Gregory Rosenthal