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Unitary $k$-designs are central to quantum information and quantum many-body physics as efficient proxies for Haar-random dynamics. We study how chaotic Hamiltonian evolution can generate unitary $k$-designs. Standard approaches typically…

Quantum Physics · Physics 2026-04-07 Yi-Neng Zhou , Tian-Gang Zhou , Julian Sonner

We provide new constructions of unitary $t$-designs for general $t$ on one qudit and $N$ qubits, and propose a design Hamiltonian, a random Hamiltonian of which dynamics always forms a unitary design after a threshold time, as a basic…

Quantum Physics · Physics 2017-04-25 Yoshifumi Nakata , Christoph Hirche , Masato Koashi , Andreas Winter

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

Unitary designs are unitary ensembles that emulate Haar-random unitary statistics. They provide a vital tool for studying quantum randomness and have found broad applications in quantum technologies. However, existing research has focused…

Quantum Physics · Physics 2026-01-06 Xiaodong Yang , Jiaqing Leng , Jun Li

We present a single-quench protocol that generates unitary $k$-designs with minimal control. A system first evolves under a random Hamiltonian $H_1$; at a switch time $t_s \geq t_{\mathrm{Th}}$ (the Thouless time), it is quenched to an…

Quantum Physics · Physics 2026-03-17 Yi-Neng Zhou , Robin Löwenberg , Julian Sonner

Random unitaries are a central object of study in quantum information, with applications to quantum computation, quantum many-body physics, and quantum cryptography. Recent work has constructed unitary designs and pseudorandom unitaries…

Quantum Physics · Physics 2025-09-29 Ben Foxman , Natalie Parham , Francisca Vasconcelos , Henry Yuen

Quantum pseudorandomness, also known as unitary designs, comprise a powerful resource for quantum computation and quantum engineering. While it is known in theory that pseudorandom unitary operators can be constructed efficiently, realizing…

Quantum Physics · Physics 2019-07-24 Jun Li , Zhihuang Luo , Tao Xin , Hengyan Wang , David Kribs , Dawei Lu , Bei Zeng , Raymond Laflamme

Unitary designs are widely used in quantum computation, but in many practical settings it suffices to construct a diagonal state design generated with unitary gates diagonal in the computational basis. In this work, we introduce a simple…

Randomness generation through quantum-chaotic evolution underpins foundational questions in statistical mechanics and applications across quantum information science, including benchmarking, tomography, metrology, and demonstrations of…

Statistical Mechanics · Physics 2026-01-01 Souradeep Ghosh , Nicholas Hunter-Jones , Joaquin F. Rodriguez-Nieva

The nature of randomness and complexity growth in systems governed by unitary dynamics is a fundamental question in quantum many-body physics. This problem has motivated the study of models such as local random circuits and their…

Quantum Physics · Physics 2025-10-10 Laura Cui , Thomas Schuster , Liang Mao , Hsin-Yuan Huang , Fernando Brandao

We study efficient generations of random diagonal-unitary matrices, an ensemble of unitary matrices diagonal in a given basis with randomly distributed phases for their eigenvalues. Despite the simple algebraic structure, they cannot be…

Quantum Physics · Physics 2014-01-31 Yoshifumi Nakata , Mio Murao

We consider the problem of estimating quantum observables on a collection of qubits, given as a linear combination of Pauli operators, with shallow quantum circuits consisting of single-qubit rotations. We introduce estimators based on…

Quantum Physics · Physics 2022-08-08 Stefan Hillmich , Charles Hadfield , Rudy Raymond , Antonio Mezzacapo , Robert Wille

The unitary design formation in random circuits has attracted considerable attention due to its wide range of practical applications and relevance to fundamental physics. While the formation rates in Haar random circuits have been…

Quantum Physics · Physics 2026-02-05 Toshihiro Yada , Ryotaro Suzuki , Yosuke Mitsuhashi , Nobuyuki Yoshioka

Unitary randomness underpins both fundamental tasks in quantum information and the modern theory of quantum chaos. On one side, a central concept is that of approximate unitary designs: circuits that look random according to small moments…

Quantum Physics · Physics 2025-10-14 Neil Dowling , Jacopo De Nardis , Markus Heinrich , Xhek Turkeshi , Silvia Pappalardi

Recent works have investigated the emergence of a new kind of random matrix behaviour in unitary dynamics following a quantum quench. Starting from a time-evolved state, an ensemble of pure states supported on a small subsystem can be…

Quantum Physics · Physics 2022-06-15 Pieter W. Claeys , Austen Lamacraft

We study the universal structure of late-time ensembles obtained from unitary dynamics in quantum chaotic systems with symmetries, such as charge or energy conservation. We find that although quantum states do not ergodically explore the…

Unitary $k$-designs are distributions of unitary gates that match the Haar distribution up to its $k$-th statistical moment. They are a crucial resource for randomized quantum protocols. However, their implementation on encoded logical…

Quantum Physics · Physics 2025-08-25 Zihan Cheng , Eric Huang , Vedika Khemani , Michael J. Gullans , Matteo Ippoliti

Unitary Designs have become a vital tool for investigating pseudorandomness since they approximate the statistics of the uniform Haar ensemble. Despite their central role in quantum information, their relation to quantum chaotic evolution…

Quantum Physics · Physics 2025-02-19 Michele Fava , Jorge Kurchan , Silvia Pappalardi

Quantum Physical Unclonable Functions (QPUFs) are hardware-based cryptographic primitives with strong theoretical security. This security stems from their modeling as Haar-random unitaries. However, implementing such unitaries on…

Quantum Physics · Physics 2025-11-25 Soham Ghosh , Holger Boche , Marc Geitz

The capacity to randomly pick a unitary across the whole unitary group is a powerful tool across physics and quantum information. A unitary $t$-design is designed to tackle this challenge in an efficient way, yet constructions to date rely…

Quantum Physics · Physics 2020-02-19 Rawad Mezher , Joe Ghalbouni , Joseph Dgheim , Damian Markham
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