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We consider the phase sensing via weak optical coherent state at quantum limit precision. A new detection scheme for the phase estimation is proposed which is inspired by the suboptimal quantum measurement in coherent optical communication.…

Quantum Physics · Physics 2016-09-28 Shuro Izumi , Masahiro Takeoka , Kentaro Wakui , Mikio Fujiwara , Kazuhiro Ema , Masahide Sasaki

This work proposes a detectability condition for linear time-varying systems based on the exponential dichotomy spectrum. The condition guarantees the existence of an observer, whose gain is determined only by the unstable modes of the…

Systems and Control · Electrical Eng. & Systems 2022-09-20 Markus Tranninger , Richard Seeber , Martin Steinberger , Martin Horn , Christian Pötzsche

The quantum nondemolition (QND) measurement is one of the most studied quantum measurement procedures. Usually, such process involves the coupling of a single system of interest, called signal, with a single probe system, so that the…

Quantum Physics · Physics 2025-05-09 Vinícius V. Seco , Alencar J. de Faria

Information-theoretic uncertainty relations formulate the joint immeasurability of two non-commuting observables in terms of information entropies. The trade-off of the accuracy in the outcome of two successive measurements manifests in…

Quantum Physics · Physics 2021-06-08 Stephan Sponar , Armin Danner , Vito Pecile , Nico Einsidler , Buelent Demirel , Yuji Hasegawa

We present a quantum thermometric protocol for the estimation of multiple temperatures within the collisional model framework. Employing the formalism of multiparameter quantum metrology, we develop a systematic strategy to estimate the…

Quantum Physics · Physics 2025-11-26 Srijon Ghosh , Sagnik Chakraborty , Rosario Lo Franco

Gaussian quantum states and channels are pivotal across many branches of quantum science and their applications, including the processing and storage of quantum information, the investigation of thermodynamics in the quantum regime, and…

Quantum Physics · Physics 2025-11-18 Alice P. G. Hall , Carlos H. S. Vieira , Jonas F. G. Santos

We derive the form of the quantum filter equation describing the continuous observation of the phase of a quantum system in an arm of an interferometer via non-demolition measurements when the statistics of an input field used for the…

Quantum Physics · Physics 2016-01-19 John Gough

Quantum non-demolition measurements facilitate various quantum technologies, including quantum communication. Notably, their operational structure can be replicated by a classical model--referred to as a noncontextual model--making it…

Quantum Physics · Physics 2026-03-31 Min Namkung , Ilhwan Kim , Hyang-Tag Lim

This paper studies an optimization-based state estimation approach for discrete-time nonlinear systems under bounded process and measurement disturbances. We first introduce a full information estimator (FIE), which is given as a solution…

Dynamical Systems · Mathematics 2015-03-18 Wuhua Hu , Lihua Xie , Keyou You

Estimation of physical observables for unknown quantum states is an important problem that underlies a wide range of fields, including quantum information processing, quantum physics, and quantum chemistry. In the context of quantum…

Quantum Physics · Physics 2024-05-21 Yuma Nakamura , Yoshichika Yano , Nobuyuki Yoshioka

A simultaneous input and state interval observer is presented for Lipschitz continuous nonlinear systems with unknown inputs and bounded noise signals for the case when the direct feedthrough matrix has full column rank. The observer…

Systems and Control · Electrical Eng. & Systems 2020-02-13 Mohammad Khajenejad , Sze Zheng Yong

We report an experimental investigation of the role of measurement in quantum metrology when the states of the probes are mixed. In particular, we investigated optimized local measurements and general global projective measurements,…

Quantum Physics · Physics 2021-02-22 R. S. Piera , S. P. Walborn , G. H. Aguilar

Phase estimation, at the heart of many quantum metrology and communication schemes, can be strongly affected by noise, whose amplitude may not be known, or might be subject to drift. Here, we investigate the joint estimation of a phase…

We develop a novel framework for costly information acquisition in which a decision-maker learns about an unobserved state by choosing a signal distribution, with the cost of information determined by the distribution of noise in the…

Theoretical Economics · Economics 2025-03-27 Peter Achim , Kemal Ozbek

We address the problem of designing simultaneous input and state interval observers for Lipschitz continuous nonlinear systems with rank-deficient feedthrough, unknown inputs and bounded noise signals. Benefiting from the existence of…

Systems and Control · Electrical Eng. & Systems 2020-12-22 Mohammad Khajenejad , Sze Zheng Yong

This work deals with the problem of designing disturbance decupled observers for the estimation of a function of the states in nonlinear systems. Necessary and sufficient conditions for the existence of lower order disturbance decoupled…

Optimization and Control · Mathematics 2023-07-19 Sunjeev Venkateswaran , Costas Kravaris

A quantum trajectory describes the evolution of a quantum system undergoing indirect measurement. In the discrete-time setting, the state of the system is updated by applying Kraus operators according to the measurement results. From an…

Quantum Physics · Physics 2022-04-04 Maël Bompais , Nina H. Amini , Clément Pellegrini

In the last years the exploitation of specific properties of quantum states has disclosed the possibility of realising tasks beyond classical limits, creating the new field of quantum technologies [1, 2, 3, 4, 5, 6, 7, 8, 9]. Among them,…

Quantum Physics · Physics 2015-06-16 E. D. Lopaeva , I. Ruo Berchera , S. Olivares , G. Brida , I. P. Degiovanni , M. Genovese

A general quantum measurement on an unknown quantum state enables us to estimate what the state originally was. Simultaneously, the measurement has a destructive effect on a measured quantum state which is reflected by the decrease of the…

Quantum Physics · Physics 2016-08-16 Ladislav Mišta , Radim Filip

A trade-off relation on our knowledge about two noncommuting observables of a qubit system in simultaneous measurement is formulated. The obtained inequality offers a quantitative information-theoretic representation of Bohr's principle of…

Quantum Physics · Physics 2009-11-13 Yuji Kurotani , Takahiro Sagawa , Masahito Ueda