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We study quantum metrology for unitary dynamics. Analytic solutions are given for both the optimal unitary state preparation starting from an arbitrary mixed state and the corresponding optimal measurement precision. This represents a…

Quantum Physics · Physics 2019-12-30 Lukas J. Fiderer , Julien M. E. Fraïsse , Daniel Braun

A Markovian master equation describing the evolution of open quantum systems in the presence of a time-dependent external field is derived within the Bloch-Redfield formalism. It leads to a system--bath interaction which depends on the…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 H. Jirari , W. Pötz

We extend here the optimization functional targeting arbitrary cat states, derived in the companion paper, to open quantum system dynamics. Applying it to a Jaynes-Cummings model with decay on the oscillator, we find, for strong dissipation…

Quantum Physics · Physics 2023-06-30 Matthias G. Krauss , Daniel M. Reich , Christiane P. Koch

The squeezed state is important in quantum metrology and quantum information. The most effective generation tool known is the optical parametric oscillator (OPO). Currently, only the squeezed states of lower-order spatial modes can be…

Quantum Physics · Physics 2020-04-22 Long Ma , Hui Guo , Hengxin Sun , Kui Liu , Bida Su , Jiangrui Gao

Fidelity is the standard measure for quantifying the similarity between two quantum states. It is equal to the square of the minimum Bhattacharyya coefficient between the probability distributions induced by quantum measurements on the two…

Quantum Physics · Physics 2025-12-01 Datong Chen , Huangjun Zhu

We propose a scheme to control and enhance atomic Bloch oscillations via photon-mediated interactions in an optical lattice supported by a standing-wave cavity with incommensurate lattice and cavity wavelengths. Our scheme uses…

Quantum Physics · Physics 2024-02-14 Haoqing Zhang , Anjun Chu , Chengyi Luo , James K. Thompson , Ana Maria Rey

Optimal quantum control theory carries a huge promise for quantum technology. Its experimental application, however, is often hindered by imprecise knowledge of the its input variables, the quantum system's parameters. We show how to…

Quantum Physics · Physics 2014-06-25 D. J. Egger , F. K. Wilhelm

Reducing decoherence is an essential step toward realizing general-purpose quantum computers beyond the present noisy intermediate-scale quantum (NISQ) computers. To this end, dynamical decoupling (DD) approaches in which external fields…

Quantum Physics · Physics 2022-09-23 Yukiyoshi Ohtsuki , Suicho Mikami , Toru Ajiki , David J. Tannor

In this paper, we demonstrate that optimal control algorithms can be used to speed up the implementation of modules of quantum algorithms or quantum simulations in networks of coupled qubits. The gain is most prominent in realistic cases,…

Quantum Physics · Physics 2008-12-20 T. Schulte-Herbrueggen , A. K. Spoerl , N. Khaneja , S. J. Glaser

We study the problem of preparing a quantum many-body system from an initial to a target state by optimizing the fidelity over the family of bang-bang protocols. We present compelling numerical evidence for a universal spin-glass-like…

Quantum Physics · Physics 2019-02-12 Alexandre G. R. Day , Marin Bukov , Phillip Weinberg , Pankaj Mehta , Dries Sels

We address the generic problem of optimal quantum state preparation for open quantum systems. It is well known that open quantum systems can be simulated by quantum trajectories described by a stochastic Schr\"odinger equation. In this…

Quantum Physics · Physics 2025-01-31 Aarón Villanueva , Hilbert Kappen

Quantum optimal control theory is a powerful tool for engineering quantum systems subject to external fields such as the ones created by intense lasers. The formulation relies on a suitable definition for a target functional, that…

Quantum Physics · Physics 2015-05-20 David Kammerlander , Alberto Castro , Miguel A. L. Marques

As an application of the simultaneous and continuous measurement of noncommutative observables formulated in our previous paper [C. Jiang and G. Watanabe, Phys. Rev. A 102, 062216 (2020)], we propose a scheme to generate the pure ideal…

Quantum Physics · Physics 2022-04-20 Chao Jiang , Gentaro Watanabe

Bosonic systems, such as photons and ultracold atoms, have played a central role in demonstrating quantum-enhanced sensing. Quantum entanglement, through squeezed and GHZ states, enables sensing beyond classical limits. However, such a…

Quantum Physics · Physics 2025-11-21 Jieqiu Shao , Diego A. R. Dalvit , Lukasz Cincio , Bharath Hebbe Madhusudhana

A new method for controlling harmonic generation, in the framework of quantum optimal control theory (QOCT), is developed. The problem is formulated in the frequency domain using a new maximization functional. The relaxation method is used…

Quantum Physics · Physics 2012-08-28 Ido Schaefer

Optical techniques for the quantum control of the dynamics of multiexciton states in a semiconductor quantum dot are explored in theory. Composite bichromatic phase-locked pulses are shown to reduce the time of elementary quantum operations…

Mesoscale and Nanoscale Physics · Physics 2009-11-07 C. Piermarocchi , Pochung Chen , Y. S. Dale , L. J. Sham

The theory of phase control of coherence, entanglement and quantum steering is developed for an optomechanical system composed of a single mode cavity containing a partially transmitting dielectric membrane and driven by short laser pulses.…

Quantum Physics · Physics 2017-12-25 F. X. Sun , D. Mao , Y. T. Dai , Z. Ficek , Q. Y. He , Q. H. Gong

We report on the efficient design of quantum optimal control protocols to manipulate the motional states of an atomic Bose-Einstein condensate (BEC) in a one-dimensional optical lattice. Our protocols operate on the momentum comb associated…

Quantum Gases · Physics 2021-10-13 N. Dupont , G. Chatelain , L. Gabardos , M. Arnal , J. Billy , B. Peaudecerf , D. Sugny , D. Guéry-Odelin

We demonstrate optimal state estimation for a cavity optomechanical system through Kalman filtering. By taking into account nontrivial experimental noise sources, such as colored laser noise and spurious mechanical modes, we implement a…

Quantum state transfer in optical microcavities plays an important role in quantum information processing, and is essential in many optical devices, such as optical frequency converter and diode. Existing schemes are effective and realized…

Optics · Physics 2019-12-03 Xu-sheng Xu , Hao Zhang , Xiang-Yu Kong , Min Wang , Gui-Lu Long