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Quantum state preparation is a central primitive in many quantum algorithms, yet it is generally resource intensive, with efficient constructions known only for structured families of states. This work introduces a method for preparing…

Quantum Physics · Physics 2026-03-26 Baptiste Claudon , Alexis Lucas , Jean-Philip Piquemal , César Feniou , Julien Zylberman

Inspired by recent advances in the manipulation of superconducting circuits coupled to mechanical modes in the quantum regime, we propose a protocol for generating superpositions of orthogonally squeezed states in a quantum harmonic…

Quantum Physics · Physics 2026-03-05 Marius K. Hope , Jonas Lidal , Francesco Massel

In recent years, quantum-enhanced machine learning has emerged as a particularly fruitful application of quantum algorithms, covering aspects of supervised, unsupervised and reinforcement learning. Reinforcement learning offers numerous…

Quantum Physics · Physics 2022-08-03 A. Hamann , V. Dunjko , S. Wölk

Quantum algorithms for ground-state energy estimation of chemical systems require a high-quality initial state. However, initial state preparation is commonly either neglected entirely, or assumed to be solved by a simple product state like…

We propose an iterative algorithm for incomplete quantum process tomography, with the help of quantum state estimation, based on the combined principles of maximum-likelihood and maximum-entropy. The algorithm yields a unique estimator for…

Quantum Physics · Physics 2012-01-04 Yong Siah Teo , Berthold-Georg Englert , Jaroslav Rehacek , Zdenek Hradil

Accurate state preparation is a critical bottleneck in many quantum algorithms, particularly those for ground state energy estimation. Even in fault-tolerant quantum computing, preparing a quantum state with sufficient overlap to the…

Quantum Physics · Physics 2025-10-07 Gwonhak Lee , Minhyeok Kang , Jungsoo Hong , Stepan Fomichev , Joonsuk Huh

I show that an optical amplifier, when combined with photon subtraction, can be used for quantum state amplification, adding noise at a level below the standard minimum. The device could be used to significantly decrease the probability of…

Quantum Physics · Physics 2011-05-17 John Jeffers

We present a probabilistic quantum algorithm for preparing mixed states which, in expectation, are proportional to the solutions of Lyapunov equations -- linear matrix equations ubiquitous in the analysis of classical and quantum dynamical…

Quantum Physics · Physics 2026-04-20 Marcello Benedetti , Ansis Rosmanis , Matthias Rosenkranz

In this article, I show that a recent family of quantum algorithms, based on the quantum amplitude amplification algorithm, can be used to describe a cognitive heuristic called availability bias. The amplitude amplification algorithm is…

Quantum Physics · Physics 2008-10-07 Riccardo Franco

Quantum state preparation initializes the quantum registers and is essential for running quantum algorithms. Designing state preparation circuits that entangle qubits efficiently with fewer two-qubit gates enhances accuracy and alleviates…

Quantum Physics · Physics 2024-09-04 Hanyu Wang , Daniel Bochen Tan , Jason Cong

We present two quantum algorithms based on evolution randomization, a simple variant of adiabatic quantum computing, to prepare a quantum state $\vert x \rangle$ that is proportional to the solution of the system of linear equations $A…

Quantum Physics · Physics 2019-02-20 Yigit Subasi , Rolando D. Somma , Davide Orsucci

We demonstrate an efficient circuit to prepare a quantum state with amplitudes proportional to a harmonic sequence. We do this by first preparing a large quantum state with linearly related amplitudes and then applying a quantum Fourier…

Quantum Physics · Physics 2026-03-02 Benjamin Rempfer , Parker Kuklinski , Justin Elenewski , Kevin Obenland

The variational preparation of complex quantum states using the quantum approximate optimization algorithm (QAOA) is of fundamental interest, and becomes a promising application of quantum computers. Here, we systematically study the…

Quantum Physics · Physics 2023-02-10 Zheng-Hang Sun , Yong-Yi Wang , Jian Cui , Heng Fan

We present a protocol for encoding $N$ real numbers stored in $N$ memory registers into the amplitudes of the quantum superposition that describes the state of $\log_2N$ qubits. This task is one of the main steps in quantum machine learning…

Quantum Physics · Physics 2022-02-07 Sahel Ashhab

In this brief paper, we go through the theoretical steps of the spectral clustering on quantum computers by employing the phase estimation and the amplitude amplification algorithms. We discuss circuit designs for each step and show how to…

Quantum Physics · Physics 2017-07-24 Ammar Daskin

Ground-state estimation lies at the heart of a broad range of quantum simulations. Most near-term approaches are cast as variational energy minimization and thus inherit the challenges of problem-specific energy landscapes. We develop the…

Quantum Physics · Physics 2025-11-18 Kyunghyun Baek , Seungjin Lee , Joonsuk Huh , Dongkeun Lee , Jinhyoung Lee , M. S. Kim , Jeongho Bang

Preparing the ground state of a given Hamiltonian and estimating its ground energy are important but computationally hard tasks. However, given some additional information, these problems can be solved efficiently on a quantum computer. We…

Quantum Physics · Physics 2020-12-16 Lin Lin , Yu Tong

Quantum amplifiers are intrinsically nonlinear systems whose performance limits are set by quantum mechanics. In quantum measurement, amplifier operation is conventionally optimized in the linear regime by maximizing signal-to-noise ratio,…

Quantum Physics · Physics 2026-03-16 Elif Cüce , Saeed A. Khan , Boris Mesits , Michael Hatridge , Hakan E. Türeci

Minimizing the use of CNOT gates in quantum state preparation is a crucial step in quantum compilation, as they introduce coupling constraints and more noise than single-qubit gates. Reducing the number of CNOT gates can lead to more…

Information Theory · Computer Science 2024-09-05 Hanyu Wang , Bochen Tan , Jason Cong , Giovanni De Micheli

A novel class of hybrid quantum-classical algorithms based on the variational approach have recently emerged from separate proposals addressing, for example, quantum chemistry and combinatorial problems. These algorithms provide an…

Quantum Physics · Physics 2017-01-09 Gian Giacomo Guerreschi , Mikhail Smelyanskiy