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We prove a nontrivial circuit-depth lower bound for preparing a low-energy state of a locally interacting quantum many-body system in two dimensions, assuming the circuit is geometrically local. For preparing any state which has an energy…

Quantum Physics · Physics 2022-10-14 Arkin Tikku , Isaac H. Kim

We introduce the magic hierarchy, a quantum circuit model that alternates between arbitrary-sized Clifford circuits and constant-depth circuits with two-qubit gates ($\textsf{QNC}^0$). This model unifies existing circuit models, such as…

Quantum Physics · Physics 2025-08-29 Natalie Parham

We prove several new lower bounds for constant depth quantum circuits. The main result is that parity (and hence fanout) requires log depth circuits, when the circuits are composed of single qubit and arbitrary size Toffoli gates, and when…

Quantum Physics · Physics 2007-05-23 Maosen Fang , Stephen Fenner , Frederic Green , Steven Homer , Yong Zhang

We show that any quantum circuit of treewidth $t$, built from $r$-qubit gates, requires at least $\Omega(\frac{n^{2}}{2^{O(r\cdot t)}\cdot \log^4 n})$ gates to compute the element distinctness function. Our result generalizes a…

Computational Complexity · Computer Science 2016-10-03 Mateus de Oliveira Oliveira

It has been known for almost 30 years that quantum circuits with interspersed depolarizing noise converge to the uniform distribution at $\omega(\log n)$ depth, where $n$ is the number of qubits, making them classically simulable. We show…

Quantum Physics · Physics 2025-10-09 Jon Nelson , Joel Rajakumar , Michael J. Gullans

Topological quantum states cannot be created from product states with local quantum circuits of constant depth and are in this sense more entangled than topologically trivial states, but how entangled are they? Here we quantify the…

Quantum Physics · Physics 2015-05-27 Yichen Huang , Xie Chen

We establish a relationship between the correlations in a many-qubit mixed state and the minimum circuit depth needed for its preparation. If the mutual information between two subsystems exceeds the mutual information between one of those…

Quantum Physics · Physics 2025-10-03 Max McGinley , Samuel J. Garratt

Recently Bravyi, Gosset and K\"onig (Science 2018) proved an unconditional separation between the computational powers of small-depth quantum and classical circuits for a relation. In this paper we show a similar separation in the…

Quantum Physics · Physics 2021-09-27 François Le Gall

The best known size lower bounds against unrestricted circuits have remained around $3n$ for several decades. Moreover, the only known technique for proving lower bounds in this model, gate elimination, is inherently limited to proving…

Computational Complexity · Computer Science 2020-12-09 Alexander Golovnev , Alexander S. Kulikov , R. Ryan Williams

In quantum computation every unitary operation can be decomposed into quantum circuits-a series of single-qubit rotations and a single type entangling two-qubit gates, such as controlled-NOT (CNOT) gates. Two measures are important when…

Quantum Physics · Physics 2011-03-07 Martin Plesch , Časlav Brukner

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

We consider the problem of finding a near ground state of a $p$-spin model with Rademacher couplings by means of a low-depth circuit. As a direct extension of the authors' recent work [Gamarnik, Jagannath, Wein 2020], we establish that any…

Computational Complexity · Computer Science 2022-01-25 David Gamarnik , Aukosh Jagannath , Alexander S. Wein

Random quantum states have various applications in quantum information science. We discover a new ensemble of quantum states that serve as an $\epsilon$-approximate state $t$-design while possessing extremely low entanglement, magic, and…

Quantum Physics · Physics 2025-12-25 Wonjun Lee , Minki Hhan , Gil Young Cho , Hyukjoon Kwon

This paper addresses the problem of finding the depth overhead that will be incurred when running quantum circuits on near-term quantum computers. Specifically, it is envisaged that near-term quantum computers will have low qubit…

Quantum Physics · Physics 2020-07-29 Steven Herbert

A crucial subroutine in quantum computing is to load the classical data of $N$ complex numbers into the amplitude of a superposed $n=\lceil \log_2N\rceil$-qubit state. It has been proven that any algorithm universally implementing this…

Quantum Physics · Physics 2021-08-13 Xiao-Ming Zhang , Man-Hong Yung , Xiao Yuan

We construct quantum circuits which exactly encode the spectra of correlated electron models up to errors from rotation synthesis. By invoking these circuits as oracles within the recently introduced "qubitization" framework, one can use…

Random quantum circuits are a central concept in quantum information theory with applications ranging from demonstrations of quantum computational advantage to descriptions of scrambling in strongly-interacting systems and black holes. The…

Quantum Physics · Physics 2021-08-23 Jonas Haferkamp , Nicholas Hunter-Jones

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

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
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