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We demonstrate a new class of frequency-entangled states generated via spontaneous parametric down-conversion under extended phase matching conditions. Biphoton entanglement with coincident signal and idler frequencies is observed over a…

Quantum Physics · Physics 2009-11-10 Onur Kuzucu , Marco Fiorentino , Marius A. Albota , Franco N. C. Wong , Franz X. Kaertner

Multiqubit entanglement is an indispensable resource for quantum information science. In particular, the entanglement of photons is of conceptual interest due to its implications in measurement-based quantum computing, communication, and…

Quantum Physics · Physics 2025-04-08 Chao-Wei Yang , Yong Yu , Jun Li , Bo Jing , Xiao-Hui Bao , Jian-Wei Pan

Proper characterization of quantum correlations in a multimode optical state is critical for applications in quantum information science; however, the most common entanglement measurements can lead to an incomplete state reconstruction.…

Ultrastrong light-matter coupling opens exciting possibilities to generate squeezed quantum states and entanglement. Here we propose a way to achieve this regime in superconducting hybrid nanostructures with ferromagnetic interlayers.…

Mesoscale and Nanoscale Physics · Physics 2023-06-07 Mikhail Silaev

Distributed quantum metrology can enhance the sensitivity for sensing spatially distributed parameters beyond the classical limits. Here we demonstrate distributed quantum phase estimation with discrete variables to achieve Heisenberg limit…

Multi-photon states from parametric down-conversion can be entangled both in polarization and photon number. Maximal high-dimensional entanglement can be concentrated from these states via photon counting. This makes them natural candidates…

Quantum Physics · Physics 2009-11-07 Gabriel A. Durkin , Christoph Simon , Dik Bouwmeester

We develop theory of realization of hybrid entanglement between discrete-variable (single photon) and continuous-variable states (coherent states). A highly transmissive beam splitter (HTBS) is used for interaction of the ingredients.…

Quantum Physics · Physics 2018-05-22 Sergey A. Podoshvedov

We analyze the nonlinear optical response of a five-level system under a novel configuration of electro-magnetically induced transparency. We show that a giant Kerr nonlinearity with a relatively large cross-phase modulation coefficient…

Quantum Physics · Physics 2009-11-11 Yun Li , Chao Hang , Lei Ma , Guoxiang Huang

The state of a two-particle system is called entangled when its quantum mechanical wave function cannot be factorized in two single-particle wave functions. Entanglement leads to the strongest counter-intuitive feature of quantum mechanics,…

Quantum Physics · Physics 2009-11-07 E. Altewischer , M. P. van Exter , J. P. Woerdman

We report on theoretical and experimental demonstration of high-efficiency coupling of two-photon entangled states produced in the nonlinear process of spontaneous parametric down conversion into a single-mode fiber. We determine…

Quantum Physics · Physics 2015-06-26 F. A. Bovino , P. Varisco , A. M. Colla , G. Castagnoli , G. Di Giuseppe , A. V. Sergienko

Entanglement, a key resource of emerging quantum technologies, describes correlations between particles that defy classical physics. It has been studied extensively on various platforms, but has remained elusive in electron microscopy.…

We show that the effect of measurement back-action results in the generation of multiple many-body spatial modes of ultracold atoms trapped in an optical lattice, when scattered light is detected. The multipartite mode entanglement…

Implementations of solid state quantum optics provide us with devices where qubits are placed at fixed positions in photonic or plasmonic one dimensional waveguides. We show that solely by controlling the position of the qubits and with the…

Mesoscale and Nanoscale Physics · Physics 2013-02-21 A. Gonzalez-Tudela , D. Porras

Entanglement between large numbers of quantum modes is the quintessential resource for future technologies such as the quantum internet. Conventionally the generation of multimode entanglement in optics requires complex layouts of…

We investigate how the entanglement properties of a two-mode state can be improved by performing a coherent superposition operation of photon subtraction and addition, proposed by Lee and Nha [Phys. Rev. A 82, 053812 (2010)], on each mode.…

Quantum Physics · Physics 2015-05-28 Su-Yong Lee , Se-Wan Ji , Ho-Joon Kim , Hyunchul Nha

The phenomenon of quantum entanglement marks one of the furthest departures from classical physics and is indispensable for quantum information processing. Despite its fundamental importance, the distribution of entanglement over long…

Quantum Physics · Physics 2021-07-27 Sebastian Ecker , Philipp Sohr , Lukas Bulla , Marcus Huber , Martin Bohmann , Rupert Ursin

The ability to efficiently characterize the spatial correlations of entangled states of light is critical for applications of many quantum technologies such as quantum imaging. Here, we demonstrate highly efficient theoretical and…

Quantum Physics · Physics 2024-10-08 Mahtab Amooei , Girish Kulkarni , Jeremy Upham , Robert W. Boyd

We propose a method that enables efficient frequency conversion of quantum information based on recently demonstrated strong parametric coupling between two single-photon pulses propagating in a slow-light atomic medium at different group…

Quantum Physics · Physics 2015-05-14 A. Gogyan , Yu. Malakyan

For entangled states of light both the amount of entanglement and the sensitivity to noise generally increase with the number of photons in the state. The entanglement-sensitivity tradeoff is investigated for a particular set of states,…

Quantum Physics · Physics 2009-11-11 S. J. van Enk

Integrated single-photon detectors open new possibilities for monitoring inside quantum photonic circuits. We present a concept for the in-line measurement of spatially-encoded multi-photon quantum states, while keeping the transmitted ones…