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We introduce Quantum Index Algebra (QIA) as a finite, index-based algebraic framework for representing and manipulating quantum operators on Hilbert spaces of dimension $2^m$. In QIA, operators are expressed as structured combinations of…

Quantum Physics · Physics 2026-01-21 A. Yu. Volkov , G. A. Koroteev , Yu. S. Volkov

We show on the example of the Arnold cat map that classical chaotic systems can be simulated with exponential efficiency on a quantum computer. Although classical computer errors grow exponentially with time, the quantum algorithm with…

Quantum Physics · Physics 2016-09-08 B. Georgeot , D. L. Shepelyansky

Image-based data is a popular arena for testing quantum machine learning algorithms. A crucial factor in realizing quantum advantage for these applications is the ability to efficiently represent images as quantum states. Here we present a…

Quantum Physics · Physics 2023-10-10 Jason Iaconis , Sonika Johri

We benchmark the performances of Qrack, an open-source software library for the high-performance classical simulation of (gate-model) quantum computers. Qrack simulates, in the Schr\"odinger picture, the exact quantum state of $n$ qubits…

Quantum Physics · Physics 2023-09-14 Daniel Strano , Benn Bollay , Aryan Blaauw , Nathan Shammah , William J. Zeng , Andrea Mari

Suppose that a quantum circuit with K elementary gates is known for a unitary matrix U, and assume that U^m is a scalar matrix for some positive integer m. We show that a function of U can be realized on a quantum computer with at most…

Quantum Physics · Physics 2023-11-27 Andreas Klappenecker , Martin Roetteler

We provide new examples of pure entangled systems related to cluster state quantum computation that can be efficiently simulated classically. In cluster state quantum computation input qubits are initialised in the `equator' of the Bloch…

Quantum Physics · Physics 2024-02-07 Sahar Atallah , Michael Garn , Sania Jevtic , Yukuan Tao , Shashank Virmani

Thus far, sparse representations have been exploited largely in the context of robustly estimating functions in a noisy environment from a few measurements. In this context, the existence of a basis in which the signal class under…

Data Structures and Algorithms · Computer Science 2009-06-26 Mohamed-Ali Belabbas , Patrick J. Wolfe

A formulation of quaternionic quantum mechanics ($\mathbb{H}$QM) is presented in terms of a real Hilbert space. Using a physically motivated scalar product, we prove the spectral theorem and obtain a novel quaternionic Fourier series. After…

Quantum Physics · Physics 2021-01-12 Sergio Giardino

We found that the actual computational time-cost of the QFT is O(n 2^n) for large n in a quantum computer using nuclear spins. The computational cost of a quantum algorithm has usually been estimated as the sum of the universal gates…

Quantum Physics · Physics 2007-05-23 A. Saito , K. Kioi , Y. Akagi , N. Hashizume , K. Ohta

This paper introduces an innovative approach for representing Gaussian fermionic states, pivotal in quantum spin systems and fermionic models, within a range of alternative quantum bases. We focus on transitioning these states from the…

Quantum Physics · Physics 2024-06-24 Babak Tarighi , Reyhaneh Khasseh , M. A. Rajabpour

A common starting point of traditional quantum algorithm design is the notion of a universal quantum computer with a scalable number of qubits. This convenient abstraction mirrors classical computations manipulating finite sets of symbols,…

Quantum Physics · Physics 2026-03-30 Lukas Brenner , Libor Caha , Xavier Coiteux-Roy , Robert Koenig

Simulating quantum many-body systems (QMBS) is one of the long-standing, highly non-trivial challenges in condensed matter physics and quantum information due to the exponentially growing size of the system's Hilbert space. To date, tensor…

Quantum Physics · Physics 2026-02-06 Belal Abouraya , Jirawat Saiphet , Fedor Jelezko , Ressa S. Said

We provide practical simulation methods for scalar field theories on a quantum computer that yield improved asymptotics as well as concrete gate estimates for the simulation and physical qubit estimates using the surface code. We achieve…

Preserving spin symmetry in variational quantum algorithms is essential for producing physically meaningful electronic wavefunctions. Implementing spin-adapted transformations on quantum hardware, however, is challenging because the…

Quantum Physics · Physics 2026-05-04 Paarth Jain , Artur F. Izmaylov , Erik R. Kjellgren

Quantum mechanics requires the operation of quantum computers to be unitary, and thus makes it important to have general techniques for developing fast quantum algorithms for computing unitary transforms. A quantum routine for computing a…

Quantum Physics · Physics 2007-05-23 Peter Hoyer

Variational Quantum algorithms, especially Quantum Approximate Optimization and Variational Quantum Eigensolver (VQE) have established their potential to provide computational advantage in the realm of combinatorial optimization. However,…

Quantum Physics · Physics 2023-07-11 Dheeraj Peddireddy , Utkarsh Priyam , Vaneet Aggarwal

Quantum signal processing (QSP), which enables systematic polynomial transformations on quantum data through sequences of qubit rotations, has emerged as a fundamental building block for quantum algorithms and data re-uploading quantum…

As the first useful Quantum Computers will be quantum simulators, here the minimum number of qubits necessary for the solution of the Schroedinger equation in simple test problems is evaluated. From the present preliminary results it…

Quantum Physics · Physics 2015-06-26 G. Strini

A potential approach for demonstrating quantum advantage is using quantum computers to simulate fermionic systems. Quantum algorithms for fermionic system simulation usually involve the Hamiltonian evolution and measurements. However, in…

Quantum Physics · Physics 2025-05-14 Qing-Song Li , Jiaxuan Zhang , Huan-Yu Liu , Qingchun Wang , Yu-Chun Wu , Guo-Ping Guo

We present a quantum algorithm that verifies a product of two n*n matrices over any field with bounded error in worst-case time n^{5/3} and expected time n^{5/3} / min(w,sqrt(n))^{1/3}, where w is the number of wrong entries. This improves…

Quantum Physics · Physics 2007-05-23 Harry Buhrman , Robert Spalek