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Entanglement is at the heart of most quantum information tasks, and therefore considerable effort has been made to find methods of deciding the entanglement content of a given bipartite quantum state. Here, we prove a fundamental limitation…

Quantum Physics · Physics 2016-06-15 Claudio Carmeli , Teiko Heinosaari , Antti Karlsson , Jussi Schultz , Alessandro Toigo

We study efficient quantum certification algorithms for quantum state set and unitary quantum channel. We present an algorithm that uses $O(\varepsilon^{-4}\ln |\mathcal{P}|)$ copies of an unknown state to distinguish whether the unknown…

Quantum Physics · Physics 2021-03-05 Wei Xie

The separability detecting problem of mixed states is one of the fundamental problems in quantum information theory. In the last 20 years, almost all methods are based on the sufficient or necessary conditions for entanglement. However, in…

Quantum Physics · Physics 2020-07-15 Ying Li , Guyan Ni

Quantum state tomography, the task of learning an unknown quantum state, is a fundamental problem in quantum information. In standard settings, the complexity of this problem depends significantly on the type of quantum state that one is…

Quantum Physics · Physics 2025-11-06 Maxime Meyer , Soumik Adhikary , Naixu Guo , Patrick Rebentrost

We study the identification of quantum phases of matter, at zero temperature, when only part of the phase diagram is known in advance. Following a supervised learning approach, we show how to use our previous knowledge to construct an…

Quantum Physics · Physics 2024-09-10 Mehran Khosrojerdi , Jason L. Pereira , Alessandro Cuccoli , Leonardo Banchi

Unambiguous discrimination and exact cloning reduce the square-overlap between quantum states, exemplifying the more general type of procedure we term state separation. We obtain the maximum probability with which two equiprobable quantum…

Quantum Physics · Physics 2008-11-26 Anthony Chefles , Stephen M. Barnett

Quantum computing is seeking to realize hardware-optimized algorithms for application-related computational tasks. NP (nondeterministic-polynomial-time) is a complexity class containing many important but intractable problems like the…

Quantum Physics · Physics 2021-08-27 Aonan Zhang , Hao Zhan , Junjie Liao , Kaimin Zheng , Tao Jiang , Minghao Mi , Penghui Yao , Lijian Zhang

In the present study, we use cross-domain classification using quantum machine learning for quantum advantages to readdress the entanglement versus separability paradigm. The inherent structure of quantum states and its relation to a…

Quantum Physics · Physics 2025-04-09 Diksha Sharma , Vivek Balasaheb Sabale , Parvinder Singh , Atul Kumar

Probabilistically creating n perfect clones from m copies for one of N priori known quantum states with minimum failure probability is a long-standing problem. We provide a rigorous proof for the geometric approach to this probabilistic…

Quantum Physics · Physics 2019-05-07 Haixin Liu , Heng Fan

The complete learning of an $n$-qubit quantum state requires samples exponentially in $n$. Several works consider subclasses of quantum states that can be learned in polynomial sample complexity such as stabilizer states or high-temperature…

Quantum Physics · Physics 2023-09-19 Liming Zhao , Naixu Guo , Ming-Xing Luo , Patrick Rebentrost

We focus on determining the separability of an unknown bipartite quantum state $\rho$ by invoking a sufficiently large subset of all possible entanglement witnesses given the expected value of each element of a set of mutually orthogonal…

Quantum Physics · Physics 2009-11-13 Lawrence M. Ioannou , Benjamin C. Travaglione

We introduce $k$-local quasi-quantum states: a superset of the regular quantum states, defined by relaxing the positivity constraint. We show that a $k$-local quasi-quantum state on $n$ qubits can be 1-1 mapped to a distribution of…

Quantum Physics · Physics 2025-01-27 Itai Arad , Miklos Santha

The linearity of quantum operations puts many fundamental constraints on the information processing tasks we can achieve on a quantum system whose state is not exactly known, just as we observe in quantum cloning and quantum discrimination.…

Quantum Physics · Physics 2009-11-11 Yuan Feng , Runyao Duan , Zhengfeng Ji

We experimentally implement a machine-learning method for accurately identifying unknown pure quantum states. The method, called single-shot measurement learning, achieves the theoretical optimal accuracy for $\epsilon = O(N^{-1})$ in state…

Quantum Physics · Physics 2021-05-05 Sang Min Lee , Hee Su Park , Jinhyoung Lee , Jaewan Kim , Jeongho Bang

The application of quantum computation to accelerate machine learning algorithms is one of the most promising areas of research in quantum algorithms. In this paper, we explore the power of quantum learning algorithms in solving an…

Quantum Physics · Physics 2023-04-19 Yusen Wu , Bujiao Wu , Jingbo Wang , Xiao Yuan

Experimental determination of an unknown quantum state usually requires several incompatible measurements. However, it is also possible to determine the full quantum state from a single, repeated measurement. For this purpose, the quantum…

Quantum Physics · Physics 2008-03-25 Xinhua Peng , Jiangfeng Du , Dieter Suter

To obtain a complete description of a quantum system, one usually employs standard quantum state tomography, which however requires exponential number of measurements to perform and hence is impractical when the system's size grows large.…

Quantum Physics · Physics 2020-01-17 Tao Xin , Xinfang Nie , Xiangyu Kong , Jingwei Wen , Dawei Lu , Jun Li

We present a review of the problem of finding out whether a quantum state of two or more parties is entangled or separable. After a formal definition of entangled states, we present a few criteria for identifying entangled states and…

Quantum Physics · Physics 2017-01-10 Sreetama Das , Titas Chanda , Maciej Lewenstein , Anna Sanpera , Aditi Sen De , Ujjwal Sen

Quantum steering can be detected via the violation of steering inequalities, which provide sufficient conditions for the steerability of quantum states. Here we discuss the converse problem, namely ensuring that a state is unsteerable, and…

Quantum Physics · Physics 2016-03-21 Joseph Bowles , Flavien Hirsch , Marco Túlio Quintino , Nicolas Brunner

Methods of processing quantum data become more important as quantum computing devices improve their quality towards fault tolerant universal quantum computers. These methods include discrimination and filtering of quantum states given as an…

Quantum Physics · Physics 2020-02-18 D. V. Babukhin , A. A. Zhukov , W. V. Pogosov