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Relaxation effects impose fundamental limitations on our ability to coherently control quantum mechanical phenomena. In this letter, we establish physical limits on how closely can a quantum mechanical system be steered to a desired target…

Quantum Physics · Physics 2009-11-10 N. Khaneja , B. Luy , S. J. Glaser

Differential sensitivity techniques originally developed to study the robustness of energy landscape controllers are generalized to the important case of closed quantum systems subject to continuously varying controls. Vanishing sensitivity…

Quantum Physics · Physics 2025-10-13 Sean Patrick O'Neil , Edmond Jonckheere , Sophie Schirmer

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

Control of quantum systems via time-varying external fields optimized to maximize a fidelity measure at a given time is a mainstay in modern quantum control. However, save for specific systems, current analysis techniques for such quantum…

Quantum Physics · Physics 2024-01-10 Sean Patrick O'Neil , Edmond Jonckheere , Sophie Schirmer

Quantum optimal control theory (QOCT) can be used to design the shape of electromagnetic pulses that implement operations on quantum devices. By using non-trivially shaped waveforms, gates can be made significantly faster than those built…

Quantum Physics · Physics 2026-02-27 Alonso Hernández-Antón , Fernando Luis , Alberto Castro

Realistic quantum sensors face a trade-off between the number of sensors measured in parallel and the control and readout fidelity ($F$) across the ensemble. We investigate how the number of sensors and fidelity affect sensitivity to…

Quantum Physics · Physics 2021-03-24 Sara Mouradian , Neil Glikin , Eli Megidish , Kai-Isaak Ellers , Hartmut Haeffner

Quantum parameter estimation is central to many fields such as quantum computation, communications and metrology. Optimal estimation theory has been instrumental in achieving the best accuracy in quantum parameter estimation, which is…

Quantum Physics · Physics 2015-06-18 Shibdas Roy , Ian R. Petersen , Elanor H. Huntington

The thermodynamic uncertainty relation posits that higher thermodynamic costs are essential for a system to function with greater precision. Recent discussions have expanded thermodynamic uncertainty relations beyond classical…

Quantum Physics · Physics 2023-12-13 Yoshihiko Hasegawa

Critical quantum metrology relies on the extreme sensitivity of a system's eigenstates near the critical point of a quantum phase transition to Hamiltonian perturbations. This means that these eigenstates are extremely sensitive to all the…

Quantum Physics · Physics 2025-06-12 George Mihailescu , Steve Campbell , Karol Gietka

Most studies in multiparameter estimation assume the dynamics is fixed and focus on identifying the optimal probe state and the optimal measurements. In practice, however, controls are usually available to alter the dynamics, which provides…

Quantum Physics · Physics 2017-10-30 Jing Liu , Haidong Yuan

Quantum control in large dimensional Hilbert spaces is essential for realizing the power of quantum information processing. For closed quantum systems the relevant input/output maps are unitary transformations, and the fundamental challenge…

Quantum Physics · Physics 2014-10-17 B. E. Anderson , H. Sosa-Martinez , C. A. Riofrío , I. H. Deutsch , P. S. Jessen

Many optimally scaling quantum simulation algorithms employ controlled time evolution of the Hamiltonian, which is typically the major bottleneck for their efficient implementation. This work establishes a compression protocol for encoding…

Quantum Physics · Physics 2026-04-09 Erenay Karacan

High precision measurements are essential to solve major scientific and technological challenges, from gravitational wave detection to healthcare diagnostics. Quantum sensing delivers greater precision, but an in-depth optimisation of…

In order to unitarily evolve a quantum system, an agent requires knowledge of time, a parameter which no physical clock can ever perfectly characterise. In this letter, we study how limitations on acquiring knowledge of time impact…

Quantum Physics · Physics 2023-10-24 Jake Xuereb , Florian Meier , Paul Erker , Mark T. Mitchison , Marcus Huber

Precision sensing, and in particular high precision magnetometry, is a central goal of research into quantum technologies. For magnetometers, often trade-offs exist between sensitivity, spatial resolution, and frequency range. The…

Quantum Physics · Physics 2016-06-22 I. Baumgart , J. -M. Cai , A. Retzker , M. B. Plenio , Ch. Wunderlich

Quantum optimal control theory is becoming increasingly crucial as quantum devices become more precise, but the need to quickly optimize these systems classically remains a significant bottleneck in their operation. Here we present a new…

Quantum Physics · Physics 2022-05-11 Mogens Dalgaard , Felix Motzoi

Optical frequency combs combine ultrashort pulse duration and phase stability, making them powerful resources for high-precision ranging even when affected by atmospheric dispersion. It has been established that by classical modal…

Quantum Physics · Physics 2026-04-08 Mylenne Manrique , Ilaria Gianani , Marco Barbieri , Valentina Parigi , Nicolas Treps

With the advent of gravitational wave detectors employing squeezed light, quantum waveform estimation---estimating a time-dependent signal by means of a quantum-mechanical probe---is of increasing importance. As is well known, backaction of…

Quantum Physics · Physics 2021-06-30 Sami Boulebnane , Mischa P. Woods , Joseph M. Renes

This paper concerns a class of uncertain linear quantum systems subject to quadratic perturbations in the system Hamiltonian. A small gain approach is used to evaluate the performance of the given quantum system. In order to get improved…

Systems and Control · Computer Science 2015-08-12 Chengdi Xiang , Ian R. Petersen , Daoyi Dong

Recent advancements in quantum technologies have highlighted the importance of mitigating system imperfections, including parameter uncertainties and decoherence effects, to improve the performance of experimental platforms. However, most…

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