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We investigate the generation of quantum states and unitary operations that are ``random'' in certain respects. We show how to use such states to estimate the average fidelity, an important measure in the study of implementations of quantum…

Quantum Physics · Physics 2007-05-23 Christoph Dankert

We introduce a task that we call partial decoupling, in which a bipartite quantum state is transformed by a unitary operation on one of the two subsystems and then is subject to the action of a quantum channel. We assume that the subsystem…

Quantum Physics · Physics 2021-10-20 Eyuri Wakakuwa , Yoshifumi Nakata

We introduce a quantum algorithm that produces approximate solutions for combinatorial optimization problems. The algorithm depends on a positive integer p and the quality of the approximation improves as p is increased. The quantum circuit…

Quantum Physics · Physics 2014-11-17 Edward Farhi , Jeffrey Goldstone , Sam Gutmann

We propose a new method to extend the size of a quantum computation beyond the number of physical qubits available on a single device. This is accomplished by randomly inserting measure-and-prepare channels to express the output state of a…

Quantum computers are reaching a level where interactions between classical and quantum computations can happen in real-time. This marks the advent of a new, broader class of quantum circuits: dynamic quantum circuits. They offer a broader…

Quantum Physics · Physics 2023-01-11 Lukas Burgholzer , Robert Wille

The ubiquity of stabilizer circuits in the design and operation of quantum computers makes techniques to verify their correctness essential. The simulation of stabilizer circuits, which aims to replicate their behavior using a classical…

Quantum Physics · Physics 2023-09-19 Vadym Kliuchnikov , Michael Beverland , Adam Paetznick

Quantum access to arbitrary classical data encoded in unitary black-box oracles underlies interesting data-intensive quantum algorithms, such as machine learning or electronic structure simulation. The feasibility of these applications…

Quantum Physics · Physics 2025-12-23 Shuchen Zhu , Aarthi Sundaram , Guang Hao Low

Numerous quantum algorithms operate under the assumption that classical data has already been converted into quantum states, a process termed Quantum State Preparation (QSP). However, achieving precise QSP requires a circuit depth that…

Quantum Physics · Physics 2024-08-13 Yilun Zhao , Bingmeng Wang , Wenle Jiang , Xiwei Pan , Bing Li , Yinhe Han , Ying Wang

Any unitary operation in quantum information processing can be implemented via a sequence of simpler steps - quantum gates. However, actual implementation of a quantum gate is always imperfect and takes a finite time. Therefore, seeking for…

Quantum Physics · Physics 2009-09-29 Michal Sedlak , Martin Plesch

We find an algorithm of numerical renormalization group for spin chain models. The essence of this algorithm is orthogonal transformation of basis states, which is useful for reducing the number of relevant basis states to create effective…

High Energy Physics - Theory · Physics 2009-11-07 Takanori Sugihara

Unitary equivariance is a natural symmetry that occurs in many contexts in physics and mathematics. Optimization problems with such symmetry can often be formulated as semidefinite programs for a $d^{p+q}$-dimensional matrix variable that…

Quantum Physics · Physics 2025-01-07 Dmitry Grinko , Maris Ozols

The creation complexity of a quantum state is the minimum number of elementary gates required to create it from a basic initial state. The creation complexity of quantum states is closely related to the complexity of quantum circuits, which…

Quantum Physics · Physics 2022-02-11 Zixuan Hu , Sabre Kais

Gate-model quantum computers can allow quantum computations in near-term implementations. The stabilization of an optimal quantum state of a quantum computer is a challenge, since it requires stable quantum evolutions via a precise…

Quantum Physics · Physics 2019-09-04 Laszlo Gyongyosi , Sandor Imre

The main promise of quantum computing is to efficiently solve certain problems that are prohibitively expensive for a classical computer. Most problems with a proven quantum advantage involve the repeated use of a black box, or oracle,…

We give an algorithm allowing to construct bases of local unitary invariants of pure k-qubit states from the knowledge of polynomial covariants of the group of invertible local filtering operations. The simplest invariants obtained in this…

Quantum Physics · Physics 2013-02-12 Frederic Toumazet , Jean-Gabriel Luque , Jean-Yves Thibon

We introduce a novel quantum programming language featuring higher-order programs and quantum controlflow which ensures that all qubit transformations are unitary. Our language boasts a type system guaranteeingboth unitarity and…

Logic in Computer Science · Computer Science 2024-03-06 Alejandro Díaz-Caro , Emmanuel Hainry , Romain Péchoux , Mário Silva

A frequent starting point of quantum computation platforms are two-state quantum systems, i.e., qubits. However, in the context of integer optimization problems, relevant to scheduling optimization and operations research, it is often more…

Quantum computation is based on implementing selected unitary transformations which represent algorithms. A generalized optimal control theory is used to find the driving field that generates a prespecified unitary transformation. The…

Quantum Physics · Physics 2009-11-07 Jose P. Palao , Ronnie Kosloff

The quantum approximate optimization algorithm (QAOA) applies two Hamiltonians to a quantum system in alternation. The original goal of the algorithm was to drive the system close to the ground state of one of the Hamiltonians. This paper…

Quantum Physics · Physics 2018-12-31 Seth Lloyd

This paper considers the problem of quantum compilation from an optimization perspective by fixing a circuit structure of CNOTs and rotation gates then optimizing over the rotation angles. We solve the optimization problem classically and…

Quantum Physics · Physics 2024-07-16 Liam Madden , Albert Akhriev , Andrea Simonetto