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The concept of quantum coherence, including various ways to quantify the degree of coherence with respect to the prescribed basis, is currently the subject of active research. The complementarity of quantum coherence in different bases was…

Quantum Physics · Physics 2017-09-08 Alexey E. Rastegin

In this work we establish rigorously a measurement uncertainty relation (MUR) for three unbiased qubit observables, which was previously shown to hold true under some presumptions. The triplet MUR states that the uncertainty, which is…

Quantum Physics · Physics 2022-11-28 Sixia Yu , Ya-Li Mao , Chang Niu , Hu Chen , Zheng-Da Li , Jingyun Fan

Quantum sensing, using quantum properties of sensors, can enhance resolution, precision, and sensitivity of imaging, spectroscopy, and detection. An intriguing question is: Can the quantum nature (quantumness) of sensors and targets be…

Quantum Physics · Physics 2020-11-30 Ping Wang , Chong Chen , Renbao Liu

Readout error models for noisy quantum devices almost universally assume that measurement noise is classical: the measurement statistics are obtained from the ideal computational-basis populations by a column-stochastic assignment matrix…

Quantum Physics · Physics 2026-05-25 Zachariah Malik , Quinn Langfitt , Zain Saleem

Noise on quantum devices is much more complex than it is commonly given credit. Far from usual models of decoherence, nearly all quantum devices are plagued both by a continuum of environments and temporal instabilities. These induce noisy…

Quantum Physics · Physics 2025-08-27 Gregory A. L. White , Petar Jurcevic , Charles D. Hill , Kavan Modi

Given a large number N of copies of a qubit state of which we wish to estimate its purity, we prove that separable-measurement protocols can be as efficient as the optimal joint-measurement one if classical communication is used. This shows…

Quantum Physics · Physics 2015-06-26 E. Bagan , M. A. Ballester , R. Munoz-Tapia , O. Romero-Isart

We introduce the notion of incompatibility witness for quantum channels, defined as an affine functional that is non-negative on all pairs of compatible channels and strictly negative on some incompatible pair. This notion extends the…

Quantum Physics · Physics 2020-01-09 Claudio Carmeli , Teiko Heinosaari , Takayuki Miyadera , Alessandro Toigo

Learning problems involving quantum data are natural candidates for demonstrating an advantage in quantum machine learning. Recent results indicate that, for certain tasks and under noiseless conditions, coherent processing of quantum data…

We introduce a new way of quantifying the degrees of incompatibility of two ob- servables in a probabilistic physical theory and, based on this, a global measure of the degree of incompatibility inherent in such theories, across all…

Quantum Physics · Physics 2013-08-23 Paul Busch , Teiko Heinosaari , Jussi Schultz , Neil Stevens

Measurements in quantum theory can fail to be jointly measurable. Like entanglement, this incompatibility of measurements is necessary but not sufficient for violating Bell inequalities. The (in)compatibility relations among a set of…

Quantum Physics · Physics 2024-11-21 Shiv Akshar Yadavalli , Nikola Andrejic , Ravi Kunjwal

Recently a problem concerning the equivalence of joint measurability and coexistence of quantum observables was solved [15]. In this paper we generalize two known joint measurability results from sharp observables to the class of extreme…

Quantum Physics · Physics 2015-08-19 Erkka Haapasalo , Juha-Pekka Pellonpää , Roope Uola

Quantum instruments describe both the classical outcome and the updated state associated with a quantum measurement. We ask whether these processes can be simulated using only a natural subset of resources, namely projective measurements on…

Quantum Physics · Physics 2025-07-24 Shishir Khandelwal , Armin Tavakoli

A quantum observable and a channel are considered compatible if they form parts of the same measurement device, otherwise they are incompatible. Constrains on compatibility between observables and channels can be quantified via relations…

Quantum Physics · Physics 2018-02-28 T. Heinosaari , D. Reitzner , T. Rybár , M. Ziman

Nuclear Magnetic Resonance (NMR) was successfully employed to test several protocols and ideas in Quantum Information Science. In most of these implementations the existence of entanglement was ruled out. This fact introduced concerns and…

Quantum Physics · Physics 2012-09-14 D. O. Soares-Pinto , R. Auccaise , J. Maziero , A. Gavini-Viana , R. M. Serra , L. C. Céleri

We consider the problem of certifying measurement incompatibility in a prepare-and-measure (PM) scenario. We present different families of sets of qubit measurements which are incompatible, but cannot lead to any quantum over classical…

Quantum Physics · Physics 2025-09-22 Sophie Egelhaaf , Jef Pauwels , Marco Túlio Quintino , Roope Uola

The Fisher information of a quantum observable is shown to be proportional to both (i) the difference of a quantum and a classical variance, thus providing a measure of nonclassicality; and (ii) the rate of entropy increase under Gaussian…

Quantum Physics · Physics 2009-10-31 Michael J. W. Hall

We study two operational approaches to quantifying incompatibility that depart significantly from the well known entropic uncertainty relation (EUR) formalism. Both approaches result in incompatibility measures that yield non-zero values…

Quantum Physics · Physics 2015-10-15 Srijita Kundu , Kaustubh Wagh , Prabha Mandayam

A central result in the foundations of quantum mechanics is the Kochen-Specker theorem. In short, it states that quantum mechanics is in conflict with classical models in which the result of a measurement does not depend on which other…

We establish a lower bound on the quantum coherence of an arbitrary quantum state in arbitrary dimension, using a noncommutativity estimator of an arbitrary observable of sub-unit norm, where the estimator is the commutator of the…

Quantum Physics · Physics 2022-06-22 Tanaya Ray , Ahana Ghoshal , Arun Kumar Pati , Ujjwal Sen

We investigate entropic uncertainty relations for two or more binary measurements, for example spin-$\frac{1}{2}$ or polarisation measurements. We argue that the effective anti-commutators of these measurements, i.e. the anti-commutators…

Quantum Physics · Physics 2014-07-30 Jędrzej Kaniewski , Marco Tomamichel , Stephanie Wehner