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In this paper, optimal control problems governed by diffusion equations with Dirichlet and Neumann boundary conditions are investigated in the framework of the gradient discretisation method. Gradient schemes are defined for the optimality…

Numerical Analysis · Mathematics 2018-10-09 Jerome Droniou , Neela Nataraj , Devika Shylaja

Quantum speed limits provide upper bounds on the rate with which a quantum system can move away from its initial state. Here, we provide a different kind of speed limit, describing the divergence of a perturbed open system from its…

Quantum Physics · Physics 2024-08-28 Benjamin Yadin , Satoya Imai , Otfried Gühne

We investigate the performance of quantum parameter estimation based on a qubit probe in a dissipative bosonic environment beyond the traditional paradigm of weak-coupling and rotating-wave approximations. By making use of an exactly…

Quantum Physics · Physics 2021-10-18 Wei Wu , Chuan Shi

Quantum sensing employs quantum resources of a sensor to attain a smaller estimation error of physical quantities than the limit constrained by classical physics. To measure a quantum reservoir, which is significant in decoherence control,…

Quantum Physics · Physics 2021-05-21 Wei Wu , Zhen Peng , Si-Yuan Bai , Jun-Hong An

We study the estimation of parameters pertaining to non-Markovian quantum open systems, such as the dissipation rate and environmental memory time. A key challenge is identifying the optimal measurement time, which must allow sufficient…

Quantum Physics · Physics 2026-04-21 Da-Wei Luo , Ting Yu

We develop dynamical non-Markovian description of quantum computing in weak coupling limit, in lowest order approximation. We show that long range memory of quantum reservoir produces strong interrelation between structure of noise and…

Quantum Physics · Physics 2009-11-07 Robert Alicki , Michal Horodecki , Pawel Horodecki , Ryszard Horodecki

We present an end-to-end quantum algorithm for simulating nonlinear dynamics described by a system of stochastic dissipative differential equations with a quadratic nonlinearity. The stochastic part of the system is modeled by a Gaussian…

Quantum Physics · Physics 2025-10-07 Sergey Bravyi , Robert Manson-Sawko , Mykhaylo Zayats , Sergiy Zhuk

Accurately estimating high-order moments of quantum states is an elementary precondition for many crucial tasks in quantum computing, such as entanglement spectroscopy, entropy estimation, spectrum estimation, and predicting non-linear…

Quantum Physics · Physics 2024-05-16 Benchi Zhao , Mingrui Jing , Lei Zhang , Xuanqiang Zhao , Yu-Ao CHen , Kun Wang , Xin Wang

We study the entanglement evolution of two coupled qubits in interaction with an external environment and in the presence of an external magnetic field with a stochastic component. The results show the expected degradation of entanglement…

Quantum Physics · Physics 2011-05-16 Demetris P. K. Ghikas , Athanasios C. Tzemos

Entanglement distillation, an essential quantum information processing task, refers to the conversion from multiple copies of noisy entangled states to a smaller number of highly entangled states. In this work, we study the non-asymptotic…

Quantum Physics · Physics 2019-10-03 Kun Fang , Xin Wang , Marco Tomamichel , Runyao Duan

Leveraging quantum effects in metrology such as entanglement and coherence allows one to measure parameters with enhanced sensitivity. However, time-dependent noise can disrupt such Heisenberg-limited amplification. We propose a…

Quantum Physics · Physics 2022-09-23 Yulong Dong , Jonathan Gross , Murphy Yuezhen Niu

Quantum sensing is commonly described as a constrained optimization problem: maximize the information gained about an unknown quantity using a limited number of particles. Important sensors including gravitational-wave interferometers and…

Quantum Physics · Physics 2020-08-05 Morgan W. Mitchell

We develop reverse versions of hypercontractive inequalities for quantum channels. By generalizing classical techniques, we prove a reverse hypercontractive inequality for tensor products of qubit depolarizing channels. We apply this to…

Quantum Physics · Physics 2016-02-24 Toby Cubitt , Michael Kastoryano , Ashley Montanaro , Kristan Temme

Second-order partial differential equations in non-divergence form are considered. Equations of this kind typically arise as subproblems for the solution of Hamilton-Jacobi-Bellman equations in the context of stochastic optimal control, or…

Numerical Analysis · Mathematics 2020-08-13 Jan Blechschmidt , Roland Herzog , Max Winkler

Non-classical states of light play a fundamental role in quantum technology. From photonic quantum computers and simulators, to quantum communication and sensing, quantum states of light enable performing tasks that may outperform their…

Adaptive filtering is a powerful class of control theoretic concepts useful in extracting information from noisy data sets or performing forward prediction in time for a dynamic system. The broad utilization of the associated algorithms…

Quantum Physics · Physics 2021-07-21 Riddhi S. Gupta , Michael J. Biercuk

We derive fundamental bounds on the maximal achievable precision in multiparameter noisy quantum metrology, valid under the most general entanglement-assisted adaptive strategy, which are tighter than the bounds obtained by a direct use of…

Quantum Physics · Physics 2022-05-27 Francesco Albarelli , Rafal Demkowicz-Dobrzanski

Measurements with randomly chosen settings determine many important properties of quantum states without the need for a shared reference frame or calibration. They naturally emerge in the context of quantum communication and quantum…

The dynamics of a two-dimensional Bose-Einstein condensate in a presence of quantum fluctuations is studied. The properties of localized density distributions, quantum droplets (QDs), are analyzed by means of the variational approach. It is…

Pattern Formation and Solitons · Physics 2021-02-03 Sherzod R. Otajonov , Eduard N. Tsoy , Fatkhulla Kh. Abdullaev

The goal of quantum metrology is the precise estimation of parameters using quantum properties such as entanglement. This estimation usually consists of three steps: state preparation, time evolution during which information of the…

Quantum Physics · Physics 2021-03-25 Shingo Kukita , Yuichiro Matsuzaki , Yasushi Kondo
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