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The most efficient known quantum circuits for preparing unitary coupled cluster states and applying Trotter steps of the arbitrary basis electronic structure Hamiltonian involve interleaved sequences of fermionic Gaussian circuits and Ising…

Quantum Physics · Physics 2021-09-13 Nicholas C. Rubin , Joonho Lee , Ryan Babbush

Many quantum algorithms rely on a quality initial state for optimal performance. Preparing an initial state for specific applications can considerably reduce the cost of probabilistic algorithms such as the well studied quantum phase…

Quantum Physics · Physics 2024-12-10 Alexandre Fleury , James Brown , Erika Lloyd , Maritza Hernandez , Isaac H. Kim

Executing quantum logic in cryogenic quantum computers requires a continuous energy supply from room-temperature control electronics. This dependence on external energy sources creates scalability limitations due to control channel density…

Quantum Physics · Physics 2026-01-28 Yaniv Kurman , Kieran Hymas , Arkady Fedorov , William J. Munro , James Quach

Quantum computers have the potential to efficiently simulate large-scale quantum systems for which classical approaches are bound to fail. Even though several existing quantum devices now feature total qubit numbers of more than one…

Quantum Physics · Physics 2023-03-29 Hongye Yu , Yusheng Zhao , Tzu-Chieh Wei

Considering recent advancements and successes in the development of efficient quantum algorithms for electronic structure calculations --- alongside impressive results using machine learning techniques for computation --- hybridizing…

Quantum Physics · Physics 2018-10-24 Rongxin Xia , Sabre Kais

We describe a quantum algorithm for preparing states that encode solutions of non-homogeneous linear partial differential equations. The algorithm is a continuous-variable version of matrix inversion: it efficiently inverts differential…

Quantum Physics · Physics 2019-09-11 Juan Miguel Arrazola , Timjan Kalajdzievski , Christian Weedbrook , Seth Lloyd

Quantum state preparation, a crucial subroutine in quantum computing, involves generating a target quantum state from initialized qubits. Arbitrary state preparation algorithms can be broadly categorized into arithmetic decomposition (AD)…

We present an approach to single-shot high-fidelity preparation of an $n$-qubit state based on neighboring optimal control theory. This represents a new application of the neighboring optimal control formalism which was originally developed…

Quantum Physics · Physics 2017-09-18 Yuchen Peng , Frank Gaitan

We study two different methods to prepare excited states on a quantum computer, a key initial step to study dynamics within linear response theory. The first method uses unitary evolution for a short time $T=\mathcal{O}(\sqrt{1-F})$ to…

Quantum Physics · Physics 2021-01-12 Alessandro Roggero , Chenyi Gu , Alessandro Baroni , Thomas Papenbrock

Preparing encoded logical states is the first step in a fault-tolerant quantum computation. Standard approaches based on concatenation or repeated measurement incur a significant time overhead. The Raussendorf-Bravyi-Harrington cluster…

Quantum Physics · Physics 2025-02-12 Thiago Bergamaschi , Yunchao Liu

Predicting properties across system parameters is an important task in quantum physics, with applications ranging from molecular dynamics to variational quantum algorithms. Recently, provably efficient algorithms to solve this task for…

Quantum Physics · Physics 2024-05-22 Štěpán Šmíd , Roberto Bondesan

Determining Hamiltonian ground states and energies is a challenging task with many possible approaches on quantum computers. While variational quantum eigensolvers are popular approaches for near term hardware, adiabatic state preparation…

Quantum Physics · Physics 2021-10-28 Vladimir Kremenetski , Tad Hogg , Stuart Hadfield , Stephen J. Cotton , Norm M. Tubman

Cloud-accessible quantum processors enable direct execution of quantum algorithms on heterogeneous hardware platforms. Unlike classical systems, however, identical quantum circuits may exhibit substantially different behavior across devices…

Quantum Physics · Physics 2026-01-12 Askar Oralkhan , Temirlan Zhaxalykov

The ability to perform entangling quantum operations with low error rates in a scalable fashion is a central element of useful quantum information processing. Neutral atom arrays have recently emerged as a promising quantum computing…

Quantum optimal control can play a crucial role to realize a set of universal quantum logic gates with error rates below the threshold required for fault-tolerance. Open-loop quantum optimal control relies on accurate modeling of the…

Quantum Physics · Physics 2018-12-05 Guanru Feng , Franklin H. Cho , Hemant Katiyar , Jun Li , Dawei Lu , Jonathan Baugh , Raymond Laflamme

Three-qubit gates are highly beneficial operations in quantum computing, enabling compact implementations of quantum algorithms and efficient generation of multipartite entangled states. However, realizing such gates with high fidelity…

Quantum Physics · Physics 2026-01-19 Guangze Chen , Anton Frisk Kockum

In this paper we discuss a quantum multi-tasking protocol for preparation of known one-qubit and two-qubit states respectively in two different locations. The ideal remote state preparation protocol is discussed in the first place in which…

Quantum Physics · Physics 2023-01-27 Binayak S. Choudhury , Manoj Kumar Mandal , Soumen Samanta , Biswanath Dolai

In the lead up to fault tolerance, the utility of quantum computing will be determined by how adequately the effects of noise can be circumvented in quantum algorithms. Hybrid quantum-classical algorithms such as the variational quantum…

Variational quantum algorithms (VQAs) are expected to establish valuable applications on near-term quantum computers. However, recent works have pointed out that the performance of VQAs greatly relies on the expressibility of the ansatzes…

Quantum Physics · Physics 2022-08-15 Xia Liu , Geng Liu , Jiaxin Huang , Hao-Kai Zhang , Xin Wang

Quantum simulation algorithms often require numerous ancilla qubits and deep circuits, prohibitive for near-term hardware. We introduce a framework for simulating quantum channels using ensembles of low-depth circuits in place of many-qubit…

Quantum Physics · Physics 2024-08-01 Joseph Peetz , Scott E. Smart , Prineha Narang