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Remote spatial indistinguishability of identical subsystems as a direct controllable quantum resource at distant sites has not been yet experimentally proven. We design a setup capable to tune the spatial indistinguishability of two photons…

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

Networking superconducting quantum computers is a longstanding challenge in quantum science. The typical approach has been to cascade transducers: converting to optical frequencies at the transmitter and to microwave frequencies at the…

We theoretically evaluate establishing remote entanglement between distinguishable matter qubits through interference and detection of two emitted photons. The fidelity of the entanglement operation is analyzed as a function of the temporal…

Quantum Physics · Physics 2016-12-02 A. M. Dyckovsky , S. Olmschenk

We report the first experimental realization of entanglement swapping over large distances in optical fibers. Two photons separated by more than two km of optical fibers are entangled, although they never directly interacted. We use two…

Quantum Physics · Physics 2009-11-10 H. de Riedmatten , I. Marcikic , J. A. W. van Houwelingen , W. Tittel , H. Zbinden , N. Gisin

Quantum entanglement is recognized as a fundamental resource in quantum information processing and is essential for understanding quantum many-body physics. However, experimentally detecting entanglement, particularly in many-particle…

Quantum Physics · Physics 2025-08-13 Hao-Yue Qi , Wei Zheng

We present two protocols for the single-photon entanglement concentration. With the help of the 50:50 beam splitter, variable beam splitter and an auxiliary photon, we can concentrate a less-entangled single-photon state into a maximally…

Quantum Physics · Physics 2012-10-01 Lan Zhou

The use of multidimensional entanglement opens new perspectives for quantum information processing. However, an important challenge in practice is to certify and characterize multidimensional entanglement from measurement data that are…

Exploiting semiconductor fabrication techniques, natural carriers of quantum information such as atoms, electrons, and photons can be embedded in scalable integrated devices. Integrated optics provides a versatile platform for large-scale…

Sensors for mapping the trajectory of an incoming particle find important utility in experimental high energy physics and searches for dark matter. For a quantum sensing protocol that uses projective measurements on a multi-qubit sensor…

Quantum Physics · Physics 2024-10-10 Zachary E. Chin , David R. Leibrandt , Isaac L. Chuang

Quantum entanglement is an essential resource for quantum science and technology. However, entanglement detection and quantification, via typical entanglement measures such as linear entanglement entropy or negativity, can be a very…

Quantum Physics · Physics 2025-06-17 Diego Fallas Padilla , Mingjian Zhu , Han Pu

Spatially entangled photon pairs (biphotons) generated by spontaneous parametric down-conversion offer unique opportunities for quantum imaging, but image-plane biphoton correlations are difficult to observe with camera-based detectors.…

Quantum Physics · Physics 2026-01-01 David McFadden , Rainer Heintzmann

We report the efficient creation and detection of hybrid entanglement between one photon's polarization and another photon's complex transverse polarization pattern. The polarization measurement of the first photon triggers a polarization…

Quantum Physics · Physics 2014-06-18 Robert Fickler , Radek Lapkiewicz , Sven Ramelow , Anton Zeilinger

We show how to detect and quantify entanglement of atoms in optical lattices in terms of correlations functions of the momentum distribution. These distributions can be measured directly in the experiments. We introduce two kinds of…

Quantum Physics · Physics 2009-11-13 K. G. H. Vollbrecht , J. I. Cirac

When shared between remote locations, entanglement opens up fundamentally new capabilities for science and technology [1, 2]. Envisioned quantum networks distribute entanglement between their remote matter-based quantum nodes, in which it…

Quantum Physics · Physics 2019-12-20 V. Krutyanskiy , M. Meraner , J. Schupp , V. Krcmarsky , H. Hainzer , B. P. Lanyon

When a photon is detected after passing through an interferometer one might wonder which path it took, and a meaningful answer can only be given if one has the means of monitoring the photon's whereabouts. We report the realization of a…

Quantum Physics · Physics 2018-08-09 Yink Loong Len , Jibo Dai , Berthold-Georg Englert , Leonid A. Krivitsky

We report on the first experimental realization of the entanglement witness for polarization entangled photons. It represents a recently discovered significant quantum information protocol which is based on few local measurements. The…

Quantum Physics · Physics 2013-05-29 M. Barbieri , F. De Martini , G. Di Nepi , P. Mataloni , G. M. D'Ariano , C. Macchiavello

We prove the unconditional security of an entanglement-based quantum-key-distribution protocol using detectors that respond to multiple modes of light and cannot distinguish between one from two or more photons. Even with such practical…

Quantum Physics · Physics 2008-04-08 Masato Koashi , Yoritoshi Adachi , Takashi Yamamoto , Nobuyuki Imoto

We propose an optimal nonlocal entanglement concentration protocol (ECP) for multi-photon systems in a partially entangled pure state, resorting to the projection measurement on an additional photon. One party in quantum communication first…

Quantum Physics · Physics 2012-02-10 Fu-Guo Deng

The possibility of nonlocal quantum communication is considered. We investigate three $gedankenexperiments$ that have variable entanglement: (1) a 4-detector polarization-entangled system, (2) a 4-detector path-entangled system, and (3) a…

Quantum Physics · Physics 2015-02-17 John G. Cramer , Nick Herbert