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Classical measurement strategies in many areas are approaching their maximum resolution and sensitivity levels, but these levels often still fall far short of the ultimate limits allowed by the laws of physics. To go further, strategies…

Quantum Physics · Physics 2015-12-09 David S. Simon

We propose a new measure of relative incompatibility for a quantum system with respect to two non-commuting observables, and call it quantumness of relative incompatibility. In case of a classical state, order of observation is…

Quantum Physics · Physics 2019-09-30 Manish Kumar Shukla , Rounak Mundra , Arun K Pati , Indranil Chakrabarty , Junde Wu

Whereas complementarity manifests itself via two incompatible observables, quantum contextuality can only be revealed via the joint measurements among at least three observables. By incorporating unsharp measurements and joint measurements…

Quantum Physics · Physics 2013-12-24 Sixia Yu , C. H. Oh

In quantum mechanics, joint measurements of non-commuting observables are only possible if a minimal unavoidable measurement uncertainty is accepted. On the other hand, correlations between non-commuting observables can exceed classical…

Quantum Physics · Physics 2019-07-24 Holger F. Hofmann

In the standard von Neumann interaction used in Quantum measurements, the chosen observable to which the environment (apparatus) entangles is exactly reproduced in the state of the environment, thereby decohering the quantum system in the…

Quantum Physics · Physics 2024-01-11 Adarsh S , P. N. Bala Subramanian , T. P. Sreeraj

Quantifying quantum mechanical uncertainty is vital for the increasing number of experiments that reach the uncertainty limited regime. We present a method for computing tight variance uncertainty relations, i.e., the optimal…

Quantum Physics · Physics 2017-11-01 René Schwonnek , Lars Dammeier , Reinhard F. Werner

Conventionally, unknown quantum states are characterized using quantum-state tomography based on strong or weak measurements carried out on an ensemble of identically prepared systems. By contrast, the use of protective measurements offers…

Quantum Physics · Physics 2016-01-25 Maximilian Schlosshauer

Quantum incompatibility, referred as the phenomenon that some quantum measurements cannot be performed simultaneously, is necessary for various quantum information processing tasks, such as nonlocality and steering. When these applications…

Quantum Physics · Physics 2024-11-19 Xiaolin Zhang , Rui Qu , Zehong Chang , Yunlong Wang , Zhenyu Guo , Min An , Hong Gao , Fuli Li , Pei Zhang

The measurement of quantum states is one of the most important problems in quantum mechanics. We introduce a quantum state tomography technique in which the state of a qubit is reconstructed, while the qubit remains undetected. The key…

Heisenberg's uncertainty principle has recently led to general measurement uncertainty relations for quantum systems: incompatible observables can be measured jointly or in sequence only with some unavoidable approximation, which can be…

Quantum Physics · Physics 2017-06-27 Alberto Barchielli , Matteo Gregoratti , Alessandro Toigo

The optimal quantum measurements for estimating different unknown parameters in a parameterized quantum state are usually incompatible with each other. Traditional approaches to addressing the measurement incompatibility issue, such as the…

Quantum Physics · Physics 2026-02-03 Sisi Zhou , Senrui Chen

Current quantum computer technology is sufficient to realize weak measurements and the corresponding concept of weak values. We demonstrate how the weak value anomaly can be tested, along with consistency and simultaneity of weak values,…

Quantum Physics · Physics 2010-02-20 Todd A. Brun , Lajos Diosi , Walter T. Strunz

In quantum theory, it is known for a pair of noncommutative observables that there is no state on which they take simultaneously definite values, and that there is no joint measurement of them. They are called preparation uncertainty and…

Quantum Physics · Physics 2020-09-02 Ryo Takakura , Takayuki Miyadera

Quantum-enhanced measurements exploit quantum mechanical effects for increasing the sensitivity of measurements of certain physical parameters and have great potential for both fundamental science and concrete applications. Most of the…

Heisenberg's uncertainty principle is one of the main tenets of quantum theory. Nevertheless, and despite its fundamental importance for our understanding of quantum foundations, there has been some confusion in its interpretation: although…

Quantum Physics · Physics 2013-05-06 Cyril Branciard

We consider the question of characterising the incompatibility of sets of high-dimensional quantum measurements. We introduce the concept of measurement incompatibility in subspaces. That is, starting from a set of measurements that is…

Indirect measurement can be used to read out the outcome of a quantum system without resorting to a straightforward approach, and it is the foundation of the measurement uncertainty relations that explain the incompatibility of conjugate…

Quantum Physics · Physics 2022-08-09 Ryo Mihashi , Yoshihiko Hasegawa

Historically, the element of uncertainty in quantum mechanics has been expressed through mathematical identities called uncertainty relations, a great many of which continue to be discovered. These relations use diverse measures to quantify…

Quantum Physics · Physics 2016-03-16 Varun Narasimhachar , Alireza Poostindouz , Gilad Gour

In quantum information theory, the reliable and effective detection of entanglement is of paramount importance. However, given an unknown state, assessing its entanglement is a challenging task. To attack this problem, we investigate the…

Quantum Physics · Physics 2015-12-09 Jochen Szangolies , Hermann Kampermann , Dagmar Bruß

Quantum state tomography (QST) aims at estimating a quantum state from averaged quantum measurements made on copies of the state. Most quantum algorithms rely on QST at some point and it is a well explored topic in the literature, mostly…

Quantum Physics · Physics 2023-01-18 François Verdeil , Yannick Deville