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As a key method in dealing with uncertainties, feedback has been understood fairly well in classical control theory. But for quantum control systems, the capability of measurement-based feedback control (MFC) has not been investigated…

Quantum Physics · Physics 2010-11-16 Bo Qi , Hao Pan , Lei Guo

We present a loop-shaping approach to coherent feedback (CF) control. By formulating the coupling between a quantum system and its environment in terms of the noise power spectrum, our method enables direct manipulation of the effective…

Quantum Physics · Physics 2026-04-03 Aoi Fujimoto , Hiroyuki Ichihara , Rina Kanamoto

In quantum metrology, one of the major applications of quantum technologies, the ultimate precision of estimating an unknown parameter is often stated in terms of the Cram\'er-Rao bound. Yet, the latter is no longer guaranteed to carry an…

We examine transmission through a quantum graph vertex to which auxiliary edges with constant potentials are attached. We find a characterization of vertex couplings for which the transmission probability from a given "input" line to a…

Mathematical Physics · Physics 2016-01-01 Ondřej Turek

We consider the role of quantum mechanics in a specific coherent control scenario, designing a "coherent control interferometer" as the essential tool that links coherent control to quantum fundamentals. Building upon this allows us to…

Quantum Physics · Physics 2014-11-27 Torsten Scholak , Paul Brumer

We use Dirac's method for the quantization of constrained systems in order to quantize a spatially flat Friedmann-Lema\^{i}tre-Robertson-Walker spacetime in the context of $f(Q)$ cosmology. When the coincident gauge is considered, the…

General Relativity and Quantum Cosmology · Physics 2021-10-22 N. Dimakis , A. Paliathanasis , T. Christodoulakis

The past few years have seen a revived interest in quantum geometrical characterizations of band structures due to the rapid development of topological insulators and semi-metals. Although the metric tensor has been connected to many…

Mesoscale and Nanoscale Physics · Physics 2023-03-07 Adrien Bouhon , Abigail Timmel , Robert-Jan Slager

We investigate nano scanning in tapping mode atomic force microscopy (AFM) under quality (Q) control via numerical simulations performed in SIMULINK. We focus on the simulation of whole scan process rather than the simulation of cantilever…

Atomic Physics · Physics 2015-06-04 Aydin Varol , Ihsan Gunev , Bilal Orun , Cagatay Basdogan

We investigate the advantage of coherent superposition of two different coded channels in quantum metrology. In a continuous variable system, we show that the Heisenberg limit $1/N$ can be beaten by the coherent superposition without the…

Quantum Physics · Physics 2021-12-15 Dong Xie , Chunling Xu , An Min Wang

This paper is concerned with constructing an optimal controller in the coherent quantum Linear Quadratic Gaussian problem. A coherent quantum controller is itself a quantum system and is required to be physically realizable. The use of…

Quantum Physics · Physics 2012-05-21 Igor G. Vladimirov , Ian R. Petersen

We analyze a quantum computer (QC) design based on nuclear spin qubits in a quasi-one-dimensional (1D) chain of non-Kramers doublet atoms. We explore the use of spatial symmetry breaking to obtain control over the local dynamics of a qubit.…

Other Condensed Matter · Physics 2009-11-10 E. Novais , A. H. Castro Neto

Information science is entering into a new era in which certain subtleties of quantum mechanics enables large enhancements in computational efficiency and communication security. Naturally, precise control of quantum systems required for…

Quantum Physics · Physics 2007-05-23 Hwang Lee , Pavel Lougovski , Jonathan P. Dowling

We develop a framework to simulate quantum field theories (QFTs) with boundaries in $(1+1)$-dimenmsional curved spacetimes by employing open spin systems. Building upon our previous work that established a mapping from spin systems to QFTs…

High Energy Physics - Theory · Physics 2026-02-23 Shunichiro Kinoshita , Keiju Murata , Daisuke Yamamoto , Ryosuke Yoshii

In physics, experiments ultimately inform us as to what constitutes a good theoretical model of any physical concept: physical space should be no exception. The best picture of physical space in Newtonian physics is given by the…

Quantum Physics · Physics 2017-09-14 Chuan Sheng Chew , Otto C. W. Kong , Jason Payne

The mathematical formalism of Quantum Mechanics is derived or "reconstructed" from more basic considerations of probability theory and information geometry. The starting point is the recognition that probabilities are central to QM: the…

Quantum Physics · Physics 2021-09-14 Ariel Caticha

Motivated by the recently demonstrated ability to attach quantum dots to polymers at well defined locations, we propose a condensed phase analog of the ion trap quantum computer: a scheme for quantum computation using chemically assembled…

Quantum Physics · Physics 2009-11-07 K. R. Brown , D. A. Lidar , K. B. Whaley

Conventional approaches for controlling open quantum systems use coherent control which affects the system's evolution through the Hamiltonian part of the dynamics. Such control, although being extremely efficient for a large variety of…

Quantum Physics · Physics 2009-05-04 Alexander Pechen , Herschel Rabitz

This paper proposes a new robust control method for quantum systems with uncertainties involving sliding mode control (SMC). Sliding mode control is a widely used approach in classical control theory and industrial applications. We show…

Quantum Physics · Physics 2009-11-03 Daoyi Dong , Ian R. Petersen

We study the transmission of a quantum particle along a straight input--output line to which a graph $\Gamma$ is attached at a point. In the point of contact we impose a singularity represented by a certain properly chosen scale-invariant…

Quantum Physics · Physics 2013-03-22 Ondřej Turek , Taksu Cheon

The Cosmic Microwave Background (CMB) data analysis and the map-making process rely heavily on the use of spherical harmonics. For suitable pixelizations of the sphere, the (forward and inverse) Fourier transform plays a crucial role in…