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Learning quantum state properties is both a fundamental and practical problem in quantum information theory. Classical shadows have emerged as an efficient method for estimating properties of unknown quantum states, with rigorous…

Quantum Physics · Physics 2026-03-30 Hugo Thomas , Ulysse Chabaud , Pierre-Emmanuel Emeriau

The Gottesman-Knill theorem asserts that quantum circuits composed solely of Clifford gates can be efficiently simulated classically. This theorem hinges on the fact that Clifford gates map Pauli strings to other Pauli strings, thereby…

Quantum Physics · Physics 2024-07-30 George Biswas

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

Shadow tomography protocols have recently emerged as powerful tools for efficient quantum state learning, aiming to reconstruct expectation values of observables with fewer resources than traditional quantum state tomography. For the…

Quantum Physics · Physics 2026-01-27 Viet T. Tran , Richard Kueng

Quantum information science strives to leverage the quantum-mechanical nature of our universe in order to achieve large improvements in certain information processing tasks. In deep-space optical communications, current receivers for the…

Quantum Physics · Physics 2020-04-16 Narayanan Rengaswamy

We prove that random 1D Clifford brickwork circuits form (in expectation) good approximate quantum error correction codes in logarithmic depth. Our proof makes use of the statistical mechanics techniques for random circuits developed by…

Quantum Physics · Physics 2026-02-25 Twan Kroll , Jonas Helsen

Stabilizer simulation can efficiently simulate an important class of quantum circuits consisting exclusively of Clifford gates. However, all existing extensions of this simulation to arbitrary quantum circuits including non-Clifford gates…

Quantum Physics · Physics 2023-11-22 Benjamin Bichsel , Anouk Paradis , Maximilian Baader , Martin Vechev

By the Gottesman-Knill Theorem, the outcome probabilities of Clifford circuits can be computed efficiently. We present an alternative proof of this result for quopit Clifford circuits (i.e., Clifford circuits on collections of $p$-level…

Quantum Physics · Physics 2021-04-13 Dax Enshan Koh , Mark D. Penney , Robert W. Spekkens

Clifford circuits -- i.e. circuits composed of only CNOT, Hadamard, and $\pi/4$ phase gates -- play a central role in the study of quantum computation. However, their computational power is limited: a well-known result of Gottesman and…

Quantum Physics · Physics 2018-06-21 Adam Bouland , Joseph F. Fitzsimons , Dax Enshan Koh

Quantum mechanics provides cryptographic primitives whose security is grounded in hardness assumptions independent of those underlying classical cryptography. However, existing proposals require low-noise quantum communication and…

Shadow tomography is a framework for constructing succinct descriptions of quantum states using randomized measurement bases, called classical shadows, with powerful methods to bound the estimators used. We recast existing experimental…

Classical shadows (CS) have emerged as a powerful way to estimate many properties of quantum states based on random measurements and classical post-processing. In their original formulation, they come with optimal (or close to) sampling…

Quantum Physics · Physics 2024-08-13 Frederic Sauvage , Martin Larocca

We prove that random quantum circuits on any geometry, including a 1D line, can form approximate unitary designs over $n$ qubits in $\log n$ depth. In a similar manner, we construct pseudorandom unitaries (PRUs) in 1D circuits in…

Quantum Physics · Physics 2025-01-07 Thomas Schuster , Jonas Haferkamp , Hsin-Yuan Huang

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 propose to represent both $n$--qubits and quantum gates acting on them as elements in the complex Clifford algebra defined on a complex vector space of dimension $2n.$ In this framework, the Dirac formalism can be realized in…

Quantum Physics · Physics 2022-03-04 Jaroslav Hrdina , Ales Navrat , Petr Vasik

Quantum circuit equivalence checking asks whether two circuits implement the same unitary. It guarantees compiler correctness and safe optimization, yet most existing approaches scale exponentially with the number of qubits or the circuit…

Quantum Physics · Physics 2026-03-16 Daisuke Sakamoto , Soshun Naito , Yusei Mori , Kosuke Mitarai

NOTE: PAPER WITHDRAWN (See Comments) The Clifford and Local Clifford groups for $d > 2$ dimensional systems have been topics of recent interest due to their applications in graph states, quantum codes, and possible applications in fast…

Quantum Physics · Physics 2012-12-07 Jacob Farinholt

We introduce a technique to estimate error-mitigated expectation values on noisy quantum computers. Our technique performs shadow tomography on a logical state to produce a memory-efficient classical reconstruction of the noisy density…

Quantum Physics · Physics 2022-03-15 Hong-Ye Hu , Ryan LaRose , Yi-Zhuang You , Eleanor Rieffel , Zhihui Wang

Efficiently estimating large numbers of non-commuting observables is an important subroutine of many quantum science tasks. We present the derandomized shallow shadows (DSS) algorithm for efficiently learning a large set of non-commuting…

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…

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