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The characterization of quantum states is a fundamental step of any application of quantum technologies. Nowadays there exist several approaches addressing this problem, also based on machine and deep learning techniques. However, all these…

Quantum Physics · Physics 2025-03-07 Diego Maragnano , Claudio Cusano , Marco Liscidini

We address a problem of identifying a given pure state with one of two reference pure states, when no classical knowledge on the reference states is given, but a certain number of copies of them are available. We assume the input state is…

Quantum Physics · Physics 2009-11-11 A. Hayashi , M. Horibe , T. Hashimoto

We show how to perform measurement-based quantum computing on qudits (high-dimensional quantum systems) using alternative resource states beyond the cluster state. Estimating overheads for gate decomposition, we find that generalizing…

Quantum Physics · Physics 2026-02-13 Alena Romanova , Wolfgang Dür

Photonic quantum technologies utilize various degrees of freedom (DOFs) of light, such as polarization, frequency, and spatial modes, to encode quantum information. In the effort of further improving channel capacity of quantum…

Quantum Physics · Physics 2026-04-30 Roey Shafran , Ron Ziv , Mordechai Segev

Practical quantum state tomography is usually performed by carrying out repeated measurements on many copies of a given state. The accuracy of the reconstruction depends strongly on the dimensionality of the system and the number of copies…

Quantum Physics · Physics 2008-07-08 Alex Ling , Antia Lamas-Linares , Christian Kurtsiefer

A longstanding belief in quantum tomography is that estimating a mixed state is far harder than estimating a pure state. This is borne out in the mathematics, where mixed state algorithms have always required more sophisticated techniques…

Quantum Physics · Physics 2025-11-21 Angelos Pelecanos , Jack Spilecki , Ewin Tang , John Wright

Quantum state smoothing is a technique for assigning a valid quantum state to a partially observed dynamical system, using measurement records both prior and posterior to an estimation time. We show that the technique is greatly simplified…

Quantum Physics · Physics 2025-09-09 Kiarn T. Laverick , Areeya Chantasri , Howard M. Wiseman

We study the distinguishability of bipartite quantum states by Positive Operator-Valued Measures with positive partial transpose (PPT POVMs). The contributions of this paper include: (1). We give a negative answer to an open problem of [M.…

Quantum Physics · Physics 2014-04-02 Nengkun Yu , Runyao Duan , Mingsheng Ying

Qubit-resolved operations and measurements are required for most current quantum information processing schemes. However, these operations can be experimentally costly due to the need for local addressing, demanding significant classical…

Quantum Physics · Physics 2026-05-26 Liang Mao , Yifei Wang , Yingfei Gu , Chengshu Li

The experimental realization of increasingly complex quantum states underscores the pressing need for new methods of state learning and verification. In one such framework, quantum state tomography, the aim is to learn the full quantum…

Quantum Physics · Physics 2025-01-30 Antonio Anna Mele , Yaroslav Herasymenko

Suppose you receive a sequence of qubits where each qubit is guaranteed to be in one of two pure states, but you do not know what those states are. Your task is to determine the states. This can be viewed as a kind of quantum state learning…

Self-testing is a powerful device-independent technique that enables one to deduce the forms of both the quantum state and the measurements involved in a physical experiment based solely on observed correlations. Although numerous schemes…

Quantum Physics · Physics 2025-08-22 Arturo Konderak , Wojciech Bruzda , Remigiusz Augusiak

We propose a quantum tomography scheme for pure qudit systems which adopts random base measurements and generative learning methods, along with a built-in fidelity estimation approach to assess the reliability of the tomographic states. We…

Quantum Physics · Physics 2020-03-25 Jun Wang , Zhao-Yu Han , Song-Bo Wang , Zeyang Li , Liang-Zhu Mu , Heng Fan , Lei Wang

The efficient and reliable verification of quantum states plays a crucial role in various quantum information processing tasks. We consider the task of verifying entangled states using one-way and two-way classical communication and…

Quantum Physics · Physics 2019-12-09 Xiao-Dong Yu , Jiangwei Shang , Otfried Gühne

The deployment of intermediate- and large-scale quantum devices necessitates the development of efficient full state tomographical techniques for quantum benchmarks. Here, we introduce a matrix filling-based method for tomography of pure…

Quantum Physics · Physics 2021-11-23 Ahmad Farooq , Junaid ur Rehman , Hyundong Shin

Quantum tomography is an essential method of the photonic technology toolbox and is routinely used for evaluation of experimentally prepared states of light and characterization of devices transforming such states. The tomography procedure…

Quantum Physics · Physics 2018-12-18 Radim Hošák , Robert Stárek , Miroslav Ježek

An arbitrary quantum-optical process (channel) can be completely characterized by probing it with coherent states using the recently developed coherent-state quantum process tomography (QPT) [Lobino et al., Science 322, 563 (2008)]. In…

Quantum Physics · Physics 2013-08-09 Xiang-Bin Wang , Zong-Wen Yu , Jia-Zhong Hu , Adam Miranowicz , Franco Nori

The reconstruction of density matrices from measurement data (quantum state tomography) is the most comprehensive method for assessing the accuracy and performance of quantum devices. Existing methods to reconstruct two-photon density…

Quantum Physics · Physics 2025-03-12 Salini Rajeev , Mayukh Lahiri

Quantum state smoothing is a technique for estimating the quantum state of a partially observed quantum system at time $\tau$, conditioned on an entire observed measurement record (both before and after $\tau$). However, this smoothing…

Quantum Physics · Physics 2020-04-14 Kiarn T. Laverick , Areeya Chantasri , Howard M. Wiseman

We investigate local distinguishability of quantum states by use of the convex analysis about joint numerical range of operators on a Hilbert space. We show that any two orthogonal pure states are distinguishable by local operations and…

Quantum Physics · Physics 2009-11-11 Yoshiko Ogata