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Quantum state tomography is a fundamental task in quantum information science, enabling detailed characterization of correlations, entanglement, and electronic structure in quantum systems. However, its exponential measurement and…

Due to the exponential complexity of the resources required by quantum state tomography (QST), people are interested in approaches towards identifying quantum states which require less effort and time. In this paper, we provide a tailored…

Information Theory · Computer Science 2017-08-02 K. Li , J. Zhang , S. Cong

Integrated photonics is a leading platform for quantum technologies including nonclassical state generation \cite{Vergyris:2016-35975:SRP, Solntsev:2014-31007:PRX, Silverstone:2014-104:NPHOT, Solntsev:2016:RPH}, demonstration of quantum…

New algorithm for quantum state estimation based on the maximum likelihood estimation is proposed. Existing techniques for state reconstruction based on the inversion of measured data are shown to be overestimated since they do not…

Quantum Physics · Physics 2009-10-30 Zdenek Hradil

Accurately establishing the state of large-scale quantum systems is an important tool in quantum information science; however, the large number of unknown parameters hinders the rapid characterisation of such states, and reconstruction…

Quantum Physics · Physics 2014-07-30 Francesco Tonolini , Susan Chan , Megan Agnew , Alan Lindsay , Jonathan Leach

Negativities in quasiprobability distributions, a foundational concept originating in quantum optics, serve as a fundamental signature of quantum nonclassicality, with entanglement quasiprobabilities offering a necessary and sufficient…

Quantum Physics · Physics 2026-03-20 Yu-Zhuo Li , Li-Chao Peng , Ke-Mi Xu

State discrimination is a key challenge in the implementation of quantum communication protocols. Most optical communication protocols rely on either coherent states of light or fragile single-photon states, making it often difficult to…

Quantum Physics · Physics 2025-09-22 Luca Razzoli , Alex Pozzoli , Alessia Allevi

The hybrid interferometer integrating an optical parametric amplifier and a beam splitter has the potential to outperform the SU(1,1) interferometer. However, photon loss remains a critical limitation for practical implementation. To…

Quantum Physics · Physics 2025-10-21 Qisi Zhou , Tao Jiang , Qingqian Kang , Teng Zhao , Xin Su , Cunjin Liu , Liyun Hu

Quantum states are successfully reconstructed using the maximum likelihood estimation on the subspace where the measured projectors reproduce the identity operator. Reconstruction corresponds to normalization of incompatible observations.…

Quantum Physics · Physics 2008-11-26 Z. Hradil , J. Summhammer , H. Rauch

Waves propagating in certain one-dimensional quasiperiodic lattices are known to exhibit a sharp localization transition. We theoretically predict and experimentally observe that the localization of light in one-dimensional photonic…

Thermal states of light are widely used in quantum optics due to their correlation properties. As is well known, their correlation properties and the photon number distribution as a whole are strongly dependent on the mode number selected…

Quantum Physics · Physics 2020-01-22 K. G. Katamadze , G. V. Avosopiants , N. A. Bogdanova , Yu. I. Bogdanov , S. P. Kulik

We investigate quantum repeater protocols based upon atomic qubit-entanglement distribution through optical coherent-state communication. Various measurement schemes for an optical mode entangled with two spatially separated atomic qubits…

Quantum Physics · Physics 2010-12-14 Peter van Loock , Norbert Lütkenhaus , W. J. Munro , Kae Nemoto

We show how group symmetries can be used to reconstruct quantum states. In our scheme for SU(1,1) states, the input field passes through a non-degenerate parametric amplifier and one measures the probability of finding the output state with…

Quantum Physics · Physics 2009-11-06 G. S. Agarwal , J. Banerji

We implement the direct sampling of negative phase-space functions via unbalanced homodyne measurement using click-counting detectors. The negativities significantly certify nonclassical light in the high-loss regime using a small number of…

Quantum Physics · Physics 2018-02-14 M. Bohmann , J. Tiedau , T. Bartley , J. Sperling , C. Silberhorn , W. Vogel

A bipartite multiphoton entangled state is created through stimulated parametric down-conversion of strong laser pulses in a nonlinear crystal. It is shown how detectors that do not resolve photon number can be used to analyze such…

Quantum Physics · Physics 2007-05-23 H. S. Eisenberg , G. Khoury , G. A. Durkin , C. Simon , D. Bouwmeester

We develop a unified theoretical framework for the efficient description of multiphoton states generated and propagating in loop-based optical networks which contain nonlinear elements. These active optical components are modeled as…

Quantum Physics · Physics 2020-08-24 M. Engelkemeier , L. Lorz , Syamsundar De , B. Brecht , I. Dhand , M. B. Plenio , C. Silberhorn , J. Sperling

This work provides a mathematical derivation of a quasi-stationary model for multimode parametric down-conversion, which was presented in [Gatti et al., Sci. Rep. 13, 16786] with heuristic arguments. The model is here derived from the 3D+1…

Quantum Physics · Physics 2024-10-04 Alessandra Gatti , Enrico Brambilla , Ottavia Jedrkiewicz

We propose a combined reconstruction-classification method for simultaneously recovering absorption and scattering in turbid media from images of absorbed optical energy. This method exploits knowledge that optical parameters are determined…

Medical Physics · Physics 2016-01-20 Emma Malone , Samuel Powell , Ben T. Cox , Simon R. Arridge

Extended phase-matching conditions for spontaneous parametric down-conversion are examined. By augmenting the conventional phase-matching conditions, they permit the creation of a class of frequency-entangled states that generalizes the…

Quantum Physics · Physics 2009-11-07 Vittorio Giovannetti , Lorenzo Maccone , Jeffrey H. Shapiro , Franco N. C. Wong

Techniques to control the quantum state of light play a crucial role in a wide range of fields, from quantum information science to precision measurements. While for electrons in solid state materials complex quantum states can be created…

Quantum Gases · Physics 2019-11-18 Christian Kurtscheid , David Dung , Erik Busley , Frank Vewinger , Achim Rosch , Martin Weitz