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The Variational Quantum Eigensolver (VQE) is a promising tool for simulating ground states of quantum many-body systems on noisy quantum computers. Its effectiveness relies heavily on the ansatz, which must be both hardware-efficient for…

Quantum Physics · Physics 2025-06-05 Alina Joch , Götz S. Uhrig , Benedikt Fauseweh

Preparing algebraically correlated ground states of quantum many-body systems is an important, yet challenging task for quantum simulation. We introduce a protocol that employs local projective measurements and unitary feedback for…

Quantum Physics · Physics 2026-03-12 Johannes Feldmeier , Yu-Jie Liu , Mikhail D. Lukin , Soonwon Choi

We propose a scheme leveraging reinforcement learning to engineer control fields for generating non-classical states. It is exemplified by the application to prepare spin-squeezed states for an open collective spin model where a linear…

Quantum Physics · Physics 2024-06-17 X. L. Zhao , Y. M. Zhao , M. Li , T. T. Li , Q. Liu , S. Guo , X. X. Yi

We show that in presence of a local and uncorrelated dephasing noise, quantum advantage can be obtained in the Fisher information-based lower bound of the minimum uncertainty in estimating parameters of the system Hamiltonian. The quantum…

Quantum Physics · Physics 2024-05-27 Aparajita Bhattacharyya , Ahana Ghoshal , Ujjwal Sen

Quantum computing potentially offers exponential speed-ups over classical computing for certain tasks. A central, outstanding challenge to making quantum computing practical is to achieve fault tolerance, meaning that computations of any…

Quantum Physics · Physics 2021-02-01 Jacob Hastrup , Kimin Park , Jonatan Bohr Brask , Radim Filip , Ulrik Lund Andersen

Quantum computation promises to provide substantial speedups in many practical applications with a particularly exciting one being the simulation of quantum many-body systems. Adiabatic state preparation (ASP) is one way that quantum…

Quantum Physics · Physics 2022-01-05 Vladimir Kremenetski , Carlos Mejuto-Zaera , Stephen J. Cotton , Norm M. Tubman

We propose a procedure for the robust preparation of maximally entangled states of identical fermionic qubits, studying the role played by particle statistics in the process. The protocol exploits externally activated noisy channels to…

Quantum Physics · Physics 2023-07-25 Matteo Piccolini , Vittorio Giovannetti , Rosario Lo Franco

We propose a general-purpose quantum algorithm for preparing ground states of quantum Hamiltonians from a given trial state. The algorithm is based on techniques recently developed in the context of solving the quantum linear systems…

Quantum Physics · Physics 2018-02-05 Yimin Ge , Jordi Tura , J. Ignacio Cirac

The preparation of $n$-qubit quantum states is a cross-cutting subroutine for many quantum algorithms, and the effort to reduce its circuit complexity is a significant challenge. In the literature, the quantum state preparation algorithm by…

Quantum Physics · Physics 2026-02-09 Giacomo Belli , Michele Amoretti

We introduce a simple yet versatile protocol to inverse engineer the time-dependent Hamiltonian in two- and three level systems. In the protocol, by utilizing a universal SU(2) transformation, a given speedup goal can be obtained with large…

Quantum Physics · Physics 2017-09-13 Bi-Hua Huang , Yi-Hao Kang , Ye-Hong Chen , Qi-Cheng Wu , Jie Song , Yan Xia

Passive qubit reset is a key primitive for quantum information processing, whereby qubits are initialized by allowing them to relax to their ground state through natural dissipation, without the need for active control or feedback. However,…

Quantum Physics · Physics 2026-02-04 Théo Lejeune , Miha Papič , John Goold , Felix C. Binder , François Damanet , Mattia Moroder

We investigate the generation of quantum states for precision metrology in noisy two-level systems. These states are obtained by optimizing a variational quantum circuit to maximize the quantum Fisher information (QFI) of the output state…

Quantum estimation of parameters defining open-system dynamics may be enhanced by using ancillas that are entangled with the probe but are not submitted to the dynamics. Here we consider the important problem of estimation of transmission…

Quantum Physics · Physics 2024-03-04 Jiaxuan Wang , Ruynet. L. de Matos Filho , Girish S. Agarwal , Luiz Davidovich

Quantum variational algorithms are one of the most promising applications of near-term quantum computers; however, recent studies have demonstrated that unless the variational quantum circuits are configured in a problem-specific manner,…

This study explores robust entangled states described using the framework of discrete Wigner functions. Notably, these states are known to outperform the Bell state in measures of entanglement in the presence of non-Markovian noise. Our…

Quantum Physics · Physics 2025-05-01 Jai Lalita , Pavithran Iyer , Subhashish Banerjee

The preparation of a given quantum state on a quantum computing register is a typically demanding operation, requiring a number of elementary gates that scales exponentially with the size of the problem. Using the adiabatic theorem for…

Quantum Physics · Physics 2025-01-14 Davide Cugini , Davide Nigro , Mattia Bruno , Dario Gerace

We propose a Hamiltonian-based quantum state preparation method implemented via a shallow parametrized quantum circuit. The approach learns the parameters of a diagonal Hamiltonian through a classical training phase, while the quantum…

Entangled atomic states, such as spin squeezed states, represent a promising resource for a new generation of quantum sensors and atomic clocks. We demonstrate that optimal control techniques can be used to substantially enhance the degree…

Quantum Physics · Physics 2016-02-03 T. Pichler , T. Caneva , S. Montangero , M. D. Lukin , T. Calarco

Optimal state transport across spin chains, which are proposed as quantum wires for information transfer in solid state quantum architectures, is an important topic for quantum technologies. In this work, we study {the remote restoring of a…

Quantum Physics · Physics 2024-01-19 E. B. Fel'dman , A. N. Pechen , A. I. Zenchuk

Fast qubit reset is essential for qubit reuse in the noisy intermediate-scale quantum computing era, yet it conflicts with the weak decoherence required for high-fidelity computation. We solve the time-optimal reset problem for a…

Quantum Physics · Physics 2026-04-24 Hong-Bo Huang , Hui Dong