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The Schmidt number of a mixed state characterizes the minimum Schmidt rank of the pure states needed to construct it. We investigate the Schmidt number of an arbitrary mixed state by constructing a Schmidt number witness that detects it. We…

Quantum Physics · Physics 2009-11-06 Anna Sanpera , Dagmar Bruss , Maciej Lewenstein

High-dimensional entanglement, captured by the Schmidt number, underpins advantages in quantum information tasks, yet a unified resource-theoretic description across different Buscemi-type operational objects has been missing. Here we…

Quantum Physics · Physics 2025-12-30 Xian Shi

In the quest of completely describing entanglement in the general case of a finite number of parties sharing a physical system of finite dimensional Hilbert space a new entanglement magnitude is introduced for its pure and mixed states:…

Quantum Physics · Physics 2009-10-31 Guifre Vidal , Rolf Tarrach

A deep understanding of quantum entanglement is vital for advancing quantum technologies. The strength of entanglement can be quantified by counting the degrees of freedom that are entangled, which results in a quantity called Schmidt…

Quantum Physics · Physics 2024-02-21 Robin Krebs , Mariami Gachechiladze

The robustness of entanglement results of Vidal and Tarrach considered the problem whereby an entangled state is mixed with a separable state so that the overall state becomes non-entangled. In general it is known that there are also cases…

Quantum Physics · Physics 2009-11-10 Michael Steiner

We study the robustness of genuine multipartite entanglement and inseparability of multipartite pure states under superposition with product pure states. We introduce the concept of the maximal and the minimal Schmidt ranks for multipartite…

Quantum Physics · Physics 2025-04-17 Hui-Hui Qin , Shao-Shuai Zhao , Shao-Ming Fei

We show that two related measures of k-coherence, called the standard and generalized robustness of k-coherence, are equal to each other when restricted to pure states. As a direct application of the result, we establish an equivalence…

Quantum Physics · Physics 2018-08-29 Nathaniel Johnston , Chi-Kwong Li , Sarah Plosker , Yiu-Tung Poon , Bartosz Regula

Adding the maximally mixed state with some weight to the entanglement system leads to disentanglement of the latter. For each predefined entangled state there exists a minimal value of this weight for which the system loses its entanglement…

Quantum Physics · Physics 2021-09-01 Yu. S. Krynytskyi , A. R. Kuzmak

I consider deterministic distinguishability of a set of orthogonal, bipartite states when only a single copy is available and the parties are restricted to local operations and classical communication, but with the additional requirement…

Quantum Physics · Physics 2009-11-13 Scott M. Cohen

A profound comprehension of quantum entanglement is crucial for the progression of quantum technologies. The degree of entanglement can be assessed by enumerating the entangled degrees of freedom, leading to the determination of a parameter…

Quantum Physics · Physics 2025-04-16 Liang Xiong , Nung-sing Sze

We study the stability of NPT property of an arbitrary pure entangled state under the mixture of arbitrary pure separable states. For bipartite pure states with Schmidt number $n$ $(n>1)$ which is NPT, we show that this state is still NPT…

Quantum Physics · Physics 2015-09-04 Bobo Hua , Xiu-Hong Gao , Ming-Jing Zhao , Shao-Ming Fei

We study robustness of bipartite entangled states that are positive under partial transposition (PPT). It is shown that almost all PPT entangled states are unconditionally robust, in the sense, both inseparability and positivity are…

Quantum Physics · Physics 2009-11-13 Somshubhro Bandyopadhyay , Sibasish Ghosh , Vwani Roychowdhury

We analyze the properties of entangled random pure states of a quantum system partitioned into two smaller subsystems of dimensions $N$ and $M$. Framing the problem in terms of random matrices with a fixed-trace constraint, we establish,…

Statistical Mechanics · Physics 2016-05-11 Pierpaolo Vivo , Mauricio P. Pato , Gleb Oshanin

Motivated by the mathematical definition of entanglement we undertake a rigorous analysis of the separability and non-distillability properties in the neighborhood of those three-qubit mixed states which are entangled and completely…

Quantum Physics · Physics 2009-11-10 Roman Orus , Rolf Tarrach

Recent efforts have focused on characterizing the set of separable states that cannot be made entangled by any global unitary transformation. Here we characterize the set of states whose entanglement content cannot be increased under any…

Quantum Physics · Physics 2026-04-06 Jofre Abellanet-Vidal , Guillem Müller-Rigat , Albert Rico , Anna Sanpera

We consider distributionally robust optimization problems where the uncertainty is modeled via a structured Wasserstein ambiguity set. Specifically, the ambiguity is restricted to product measures $P^{\otimes N}$, where $P$ lies within a…

Optimization and Control · Mathematics 2026-04-14 Andrey Kharitenko , Marta Fochesato , Anastasios Tsiamis , Niklas Schmid , John Lygeros

There is an ongoing effort to quantify entanglement of quantum pure states for systems with more than two subsystems. We consider three approaches to this problem for three-qubit states: choosing a basis which puts the state into a standard…

Quantum Physics · Physics 2009-11-06 Todd A. Brun , Oliver Cohen

We introduce the notion of a Schmidt number of a bipartite density matrix, characterizing the minimum Schmidt rank of the pure states that are needed to construct the density matrix. We prove that Schmidt number is nonincreasing under local…

Quantum Physics · Physics 2009-10-31 Barbara M. Terhal , Pawel Horodecki

In this study, we enhance the understanding of entanglement transformations and their quantification by extending the concept of Schmidt vector from pure to mixed bipartite states, exploiting the lattice structure of majorization. The…

Quantum Physics · Physics 2024-07-25 F. Meroi , M. Losada , G. M. Bosyk

Genuine high-dimensional entanglement, i.e. the property of having a high Schmidt number, constitutes a resource in quantum communication, overcoming limitations of low-dimensional systems. States with a positive partial transpose (PPT), on…

Quantum Physics · Physics 2018-11-21 Marcus Huber , Ludovico Lami , Cécilia Lancien , Alexander Müller-Hermes
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