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"Help bits" are some limited trusted information about an instance or instances of a computational problem that may reduce the computational complexity of solving that instance or instances. In this paper, we study the value of help bits in…

Computational Complexity · Computer Science 2017-01-12 Salman Beigi , Omid Etesami , Amin Gohari

We show two results about the relationship between quantum and classical messages. Our first contribution is to show how to replace a quantum message in a one-way communication protocol by a deterministic message, establishing that for all…

Quantum Physics · Physics 2014-04-17 Hartmut Klauck , Supartha Podder

Quantum signal processing is a powerful framework in quantum algorithms, playing a central role in Hamiltonian simulation and related applications. The sequence of polynomials implemented at each step of this protocol provides a polynomial…

Quantum Physics · Physics 2026-05-08 Pierre-Antoine Bernard , Nathan Wiebe

Although a universal quantum computer is still far from reach, the tremendous advances in controllable quantum devices, in particular with solid-state systems, make it possible to physically implement "quantum simulators". Quantum…

Quantum Physics · Physics 2016-06-08 Zhixin Wang , Xiu Gu , Lian-Ao Wu , Yu-xi Liu

Hybrid quantum systems with different particle species are fundamental in quantum materials and quantum information science. In this work, we establish a rigorous theoretical framework proving that, given access to an unknown spin-boson…

Quantum Physics · Physics 2025-05-01 Lixing Zhang , Ze-Xun Lin , Prineha Narang , Di Luo

We study the problem of learning a Hamiltonian $H$ to precision $\varepsilon$, supposing we are given copies of its Gibbs state $\rho=\exp(-\beta H)/\operatorname{Tr}(\exp(-\beta H))$ at a known inverse temperature $\beta$. Anshu,…

Quantum Physics · Physics 2025-10-14 Jeongwan Haah , Robin Kothari , Ewin Tang

From the existence of an efficient quantum algorithm for factoring, it is likely that quantum computation is intrinsically more powerful than classical computation. At present, the best upper bound known for the power of quantum computation…

Quantum Physics · Physics 2015-09-14 Ciarán M. Lee , Jonathan Barrett

Ground states of local Hamiltonians can be generally highly entangled: any quantum circuit that generates them (even approximately) must be sufficiently deep to allow coupling (entanglement) between any pair of qubits. Until now this…

Quantum Physics · Physics 2019-07-22 Lior Eldar , Aram W. Harrow

The Polynomial-Time Hierarchy ($\mathsf{PH}$) is a staple of classical complexity theory, with applications spanning randomized computation to circuit lower bounds to ''quantum advantage'' analyses for near-term quantum computers.…

Computational Complexity · Computer Science 2024-09-04 Avantika Agarwal , Sevag Gharibian , Venkata Koppula , Dorian Rudolph

We construct a simple translationally invariant, nearest-neighbor Hamiltonian on a chain of 10-dimensional qudits that makes it possible to realize universal quantum computing without any external control during the computational process.…

Quantum Physics · Physics 2009-11-13 Daniel Nagaj , Pawel Wocjan

Polymer quantization is a non-standard representation of the quantum mechanics that inspired by loop quantum gravity. To study the associated statistical mechanics, one needs to find microstates' energies which are eigenvalues of the…

General Relativity and Quantum Cosmology · Physics 2015-06-18 M. A. Gorji , Kourosh Nozari , B. Vakili

Estimating ground state energies of many-body Hamiltonians is a central task in many areas of quantum physics. In this work, we give quantum algorithms which, given any $k$-body Hamiltonian $H$, compute an estimate for the ground state…

The ground state properties of quantum many-body systems are a subject of interest across chemistry, materials science, and physics. Thus, algorithms for finding ground states can have broad impacts. Variational quantum algorithms are one…

Quantum Physics · Physics 2023-09-28 James B. Larsen , Matthew D. Grace , Andrew D. Baczewski , Alicia B. Magann

Principal component analysis is an important dimension reduction technique in machine learning. In [S. Lloyd, M. Mohseni and P. Rebentrost, Nature Physics 10, 631-633, (2014)], a quantum algorithm to implement principal component analysis…

Quantum Physics · Physics 2019-04-09 Changpeng Shao

This work introduces a rigorous notion of localization probability of a quantum state within a given subspace of its Hilbert space. A non-negative operator A is uniquely decomposed as A=B+C, where B is the maximal positive operator…

Quantum Physics · Physics 2026-05-19 L. L. Salcedo

Let f:{-1,1}^n -> R be a real function on the hypercube, given by its discrete Fourier expansion, or, equivalently, represented as a multilinear polynomial. We say that it is Boolean if its image is in {-1,1}. We show that every function on…

Discrete Mathematics · Computer Science 2013-11-13 Tom Gur , Omer Tamuz

The famous no-cloning principle has been shown recently to enable a number of uncloneable functionalities. Here we address for the first time unkeyed quantum uncloneablity, via the study of a complexity-theoretic tool that enables a…

Quantum Physics · Physics 2024-10-14 Anne Broadbent , Martti Karvonen , Sébastien Lord

Given the Hamiltonian, the evaluation of unitary operators has been at the heart of many quantum algorithms. Motivated by existing deterministic and random methods, we present a hybrid approach, where Hamiltonians with large amplitude are…

Quantum Physics · Physics 2021-09-17 Shi Jin , Xiantao Li

Verification is a task to check whether a given quantum state is close to an ideal state or not. In this paper, we show that a variety of many-qubit quantum states can be verified with only sequential single-qubit measurements of Pauli…

Quantum Physics · Physics 2018-06-13 Yuki Takeuchi , Tomoyuki Morimae

Modeling non-Hermitian Hamiltonians is increasingly important in classical and quantum domains, especially when studying open systems, $PT$ symmetry, and resonances. However, the quantum simulation of these models has been limited by the…

Quantum Physics · Physics 2025-02-20 Anastashia Jebraeilli , Michael R. Geller