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We consider random quantum circuits (RQC) on arbitrary connected graphs whose edges determine the allowed $2$-qudit interactions. Prior work has established that such $n$-qudit circuits with local dimension $q$ on 1D, complete, and…

Quantum Physics · Physics 2023-10-31 Shivan Mittal , Nicholas Hunter-Jones

Parameterized quantum circuits (PQCs) are a central component of many variational quantum algorithms, yet there is a lack of understanding of how their parameterization impacts algorithm performance. We initiate this discussion by using…

Quantum Physics · Physics 2022-08-24 Amara Katabarwa , Sukin Sim , Dax Enshan Koh , Pierre-Luc Dallaire-Demers

We give quantum circuits that simulate an arbitrary two-qubit unitary operator up to global phase. For several quantum gate libraries we prove that gate counts are optimal in worst and average cases. Our lower and upper bounds compare…

Quantum Physics · Physics 2013-05-29 Vivek V. Shende , Igor L. Markov , Stephen S. Bullock

Quantum chaos is central to understanding quantum dynamics and is crucial for generating random quantum states, a key resource for quantum information tasks. In this work, we introduce a new class of quantum many-body dynamics, termed…

Quantum Physics · Physics 2025-07-25 Wonjun Lee , Hyukjoon Kwon , Gil Young Cho

Building a quantum computer is a daunting challenge since it requires good control but also good isolation from the environment to minimize decoherence. It is therefore important to realize quantum gates efficiently, using as few operations…

Quantum Physics · Physics 2019-10-28 T. Bækkegaard , L. B. Kristensen , N. J. S. Loft , C. K. Andersen , D. Petrosyan , N. T. Zinner

We perform optimal-control-theory calculations to determine the minimum number of two-qubit CNOT gates needed to perform quantum state preparation and unitary operator synthesis for few-qubit systems. By considering all possible gate…

Quantum Physics · Physics 2022-08-24 Sahel Ashhab , Naoki Yamamoto , Fumiki Yoshihara , Kouichi Semba

Unitary $2$-designs are random unitaries simulating up to the second order statistical moments of the uniformly distributed random unitaries, often referred to as Haar random unitaries. They are used in a wide variety of theoretical and…

Quantum Physics · Physics 2017-06-01 Yoshifumi Nakata , Christoph Hirche , Ciara Morgan , Andreas Winter

Quantum variational circuits have gained significant attention due to their applications in the quantum approximate optimization algorithm and quantum machine learning research. This work introduces a novel class of classical probabilistic…

Quantum Physics · Physics 2025-09-17 Gal Weitz , Lirandë Pira , Chris Ferrie , Joshua Combes

The variational quantum eigensolver is a prominent hybrid quantum-classical algorithm expected to impact near-term quantum devices. They are usually based on a circuit ansatz consisting of parameterized single-qubit gates and fixed…

Quantum Physics · Physics 2022-10-13 S. E. Rasmussen , N. T. Zinner

The spectral gap of local random quantum circuits is a fundamental property that determines how close the moments of the circuit's unitaries match those of a Haar random distribution. When studying spectral gaps, it is common to bound these…

Quantum Physics · Physics 2025-12-19 Andrew E. Deneris , Pablo Bermejo , Paolo Braccia , Lukasz Cincio , M. Cerezo

We show a certain kind of non-local operations can be simulated by sampling a set of local operations with a quasi-probability distribution when the task of a quantum circuit is to evaluate an expectation value of observables. Utilizing the…

Quantum Physics · Physics 2022-03-14 Kosuke Mitarai , Keisuke Fujii

Quantum key distribution allows for the generation of a secret key between distant parties connected by a quantum channel such as optical fibre or free space. Unfortunately, the rate of generation of a secret key by direct transmission is…

Standard compilers for quantum circuits decompose arbitrary single-qubit gates into a sequence of physical X(pi/2) pulses and virtual-Z phase gates. Consequently, many circuit classes implement different logic operations but have an…

As experimental platforms for quantum information processing continue to mature, characterization of the quality of unitary gates that can be applied to their quantum bits (qubits) becomes essential. Eventually, the quality must be…

We simulate the effects of different types of noise in state preparation circuits of variational quantum algorithms. We first use a variational quantum eigensolver to find the ground state of a Hamiltonian in presence of noise, and adopt…

Quantum Physics · Physics 2021-08-11 Enrico Fontana , Nathan Fitzpatrick , David Muñoz Ramo , Ross Duncan , Ivan Rungger

We study the approximate state preparation problem on noisy intermediate-scale quantum (NISQ) computers by applying a genetic algorithm to generate quantum circuits for state preparation. The algorithm can account for the specific…

Quantum Physics · Physics 2023-05-10 Tom Rindell , Berat Yenilen , Niklas Halonen , Arttu Pönni , Ilkka Tittonen , Matti Raasakka

Measurement based (MB) quantum computation allows for universal quantum computing by measuring individual qubits prepared in entangled multipartite states, known as graph states. Unless corrected for, the randomness of the measurements…

Quantum Physics · Physics 2018-02-28 Rawad Mezher , Joe Ghalbouni , Joseph Dgheim , Damian Markham

We study pseudorandomness properties of permutations on $\{0,1\}^n$ computed by random circuits made from reversible $3$-bit gates (permutations on $\{0,1\}^3$). Our main result is that a random circuit of depth $n \cdot \tilde{O}(k^2)$,…

Computational Complexity · Computer Science 2025-02-13 William He , Ryan O'Donnell

We show it is possible to obtain quantum pseudorandomness and pseudoentanglement from random subset states -- i.e. quantum states which are equal superpositions over (pseudo)random subsets of strings. This answers an open question of…

Quantum Physics · Physics 2023-12-15 Tudor Giurgica-Tiron , Adam Bouland

Current quantum computers suffer from a limited number of qubits and high error rates, limiting practical applicability. Different techniques exist to mitigate these effects and run larger algorithms. In this work, we analyze one of these…

Quantum Physics · Physics 2026-02-04 Michel Meulen , Niels M. P. Neumann , Jasper Verbree