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We simulate the dynamics of systems with $N$ = 1-20 qubits coupled to a cavity in order to assess their potential for quantum metrology of a parameter in the open systems limit. The qubits and the cavity are both allowed to have losses and…

Quantum Physics · Physics 2026-03-19 Quinn Langfitt , Zain H. Saleem , Tian Zhong , Anil Shaji , Stephen K. Gray

Multipartite quantum states constitute the key resource for quantum computation. The understanding of their internal structure is thus of great importance in the field of quantum information. This paper aims at examining the structure of…

Quantum Physics · Physics 2023-08-09 Arthur Vesperini

We establish a quantitative relation between local spin polarization and quantum entanglement in two-qubit systems by deriving an upper bound on the concurrence at fixed local polarizations, showing that increasing polarization constrains…

High Energy Physics - Phenomenology · Physics 2026-05-25 Yu-Xuan Liu , Wei Qi , Luo-Ting He , Bo-Wen Xiao

Entanglement in incoherent mixtures of pure states of two qubits is considered via the concurrence measure. A set of pure states is optimal if the concurrence for any mixture of them is the weighted sum of the concurrences of the generating…

Quantum Physics · Physics 2011-08-11 K. V. Shuddhodan , M. S. Ramkarthik , Arul Lakshminarayan

We present a protocol that allows us to obtain the concurrence of any two qubit pure state by performing a minimal and optimal tomography of one of the subsystems through measuring a single observable of an ancillary four dimensional qudit.…

Quantum Physics · Physics 2009-11-13 A. Salles , F. de Melo , J. C. Retamal , R. L. de Matos Filho , N. Zagury

Quantum entanglement is a crucial resource in quantum information processing, advancing quantum technologies. The greater the uncertainty in subsystems' pure states, the stronger the quantum entanglement between them. From the dual form of…

Quantum Physics · Physics 2026-01-01 Dong-Ping Xuan , Zhong-Xi Shen , Wen Zhou , Zhi-Xi Wang , Shao-Ming Fei

Enhancing the quantum correlations in realistic quantum systems interacting with the environment of finite temperature is an important subject in quantum information processing. In this paper, we use weak measurement and measurement…

Quantum Physics · Physics 2014-06-25 Nasibollah Doustimotlagh , Shuhao Wang , Chenglong You , Gui-Lu Long

Since entanglement is not an observable per se, measuring its value in practice is a difficult task. Here we propose a protocol for quantifying a particular entanglement measure, namely concurrence, of an arbitrary two-qubit pure state via…

Quantum Physics · Physics 2017-05-10 Mikko Tukiainen , Hirokazu Kobayashi , Yutaka Shikano

Entanglement is a fundamental feature of quantum mechanics and holds great promise for enhancing metrology and communications. Much of the focus of quantum metrology so far has been on generating highly entangled quantum states that offer…

We propose a general framework to compare the values of a physical quantity pertaining to two - or more - physical setups, in the finite-precision scenario. Such a situation requires us to compare between two "patches" on the real line…

Quantum Physics · Physics 2025-10-29 Anindita Sarkar , Paranjoy Chaki , Priya Ghosh , Ujjwal Sen

We examine the complementarity among coherence (visibility), predictability, and entanglement for qubit and qutrit systems subjected to noisy quantum channels. Using the system-path entanglement framework, analytical expressions for all…

Quantum Physics · Physics 2025-12-01 Pratidhwani Swain , Ramita Sarkar , Sukanta K. Tripathy , Prasanta K. Panigrahi

Peculiarities of multiqubit measurement are for the most part similar to peculiarities of measurement for qudit -- quantum object with finite-dimensional Hilbert space. Three different interpretations of measurement concept are analysed.…

Quantum Physics · Physics 2024-06-13 Constantin Usenko

We present a quantum circuit that implements a non-demolition measurement of complementary single- and bi-partite properties of a two-qubit system: entanglement and single-partite visibility and predictability. The system must be in a pure…

Quantum Physics · Physics 2007-06-20 F. de Melo , S. P. Walborn , János A. Bergou , L. Davidovich

We investigate optimal discrimination between two projective single-qubit measurements in a scenario where the measurement can be performed only once. We consider general setting involving a tunable fraction of inconclusive outcomes and we…

Quantum Physics · Physics 2014-12-01 M. Mikova , M. Sedlak , I. Straka , M. Micuda , M. Ziman , M. Jezek , M. Dusek , J. Fiurasek

We investigate entanglement sharing in a two-qubit sequential measurement scenario using three complementary classical correlation metrics: mutual information (I), sum of conditional probabilities (S), and the Pearson correlation…

Quantum Physics · Physics 2025-10-06 Zinuo Cai , Changliang Ren

Quantitative characterization of two-qubit entanglement purification protocols is introduced. Our approach is based on the concurrence and the hit-and-run algorithm applied to the convex set of all two-qubit states. We demonstrate that…

Quantum Physics · Physics 2024-09-04 Francesco Preti , József Zsolt Bernád

Measuring entanglement is a demanding task that usually requires full tomography of a quantum system, involving a number of observables that grows exponentially with the number of parties. Recently, it was suggested that adding a single…

Local or nonlocal character of quantum states can be quantified and is subject to various bounds that can be formulated as complementarity relations. Here, we investigate the local vs. nonlocal character of pure three-qubit states by a…

Quantum Physics · Physics 2008-11-19 Xinhua Peng , Jingfu Zhang , Jiangfeng Du , Dieter Suter

We study the entanglement between a certain qubit and the remaining system in rank- 2 mixed states prepared on the quantum computer. The protocol, which we propose for this purpose, is based on the relation of geometric measure of…

Quantum Physics · Physics 2021-05-24 A. R. Kuzmak , V. M. Tkachuk

As the fundamental tool in quantum information science, the uncertainty principle is essential for manifesting nonclassical properties of quantum systems. Plenty of efforts on the uncertainty principle with two observables have been…