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Quantum-cryptography key distribution (QCKD) experiments have been recently reported using polarization-entangled photons. However, in any practical realization, quantum systems suffer from either unwanted or induced interactions with the…

Quantum Physics · Physics 2009-11-07 S. Castelletto , I. P. Degiovanni , M. L. Rastello

We propose an efficient quantum key distribution protocol based on the photon-pair generation from parametric down-conversion (PDC). It uses the same experimental setup as the conventional protocol, but a refined data analysis enables…

Quantum Physics · Physics 2009-11-13 Yoritoshi Adachi , Takashi Yamamoto , Masato Koashi , Nobuyuki Imoto

Cavity-enhanced Spontaneous parametric down-conversion (SPDC) is capable of efficient generation of single photons with suitable spectral properties for interfacing with the atoms. However, beside the remarkable progress of this technique,…

Quantum Physics · Physics 2019-10-29 Amir Moqanaki , Francesco Massa , Philip Walther

We demonstrate a point-to-point clock synchronization protocol based on bidirectionally exchanging photons produced in spontaneous parametric down conversion (SPDC). The technique exploits tight timing correlations between photon pairs to…

Polarization-entangled photon pairs can be efficiently prepared into pure Bell states with a high fidelity via type-II spontaneous parametric down-conversion (SPDC) of narrow-band pump light. However, the use of femtosecond pump pulses to…

Quantum Physics · Physics 2007-05-23 Hou Shun Poh , Chune Yang Lum , Ivan Marcikic , Antia Lamas-Linares , Christian Kurtsiefer

Quantum entanglement of two photons created by spontaneous parametric downconversion (SPDC) can be used to probe quantum optical phenomena during a single cycle of light. Harris [Phys. Rev. Lett. 98, 063602 (2007)] suggested using…

Cavity-assisted spontaneous parametric down-conversion (SPDC) and spontaneous four-wave mixing (SFWM) in nonlinear optical materials are practical and versatile methods to generate narrowband time-energy entangled photon pairs. Time-energy…

Chromatic dispersion is one of the main limitations to the security of quantum communication protocols that rely on the transmission of single photons in single mode fibers. This phenomenon forces the trusted parties to define longer…

Quantum Physics · Physics 2017-02-14 Karolina Sedziak , Mikołaj Lasota , Piotr Kolenderski

A theoretical study of the performance of single-mode coupled spontaneous parametric downconversion sources is proposed, which only requires very few assumptions of practical interest : narrow-bandwidth and quasi-degenerate collinear…

Modeling and simulations of entanglement-based quantum-networking protocols commonly assume perfect entangled states. Some investigations have been performed which show how imperfections cause the efficiency of the protocols to rapidly…

Quantum Physics · Physics 2022-06-28 Randy Lafler , R. Nicholas Lanning

Entanglement-based QKD protocols require robust and stable photon pair sources in terms of high heralding efficiencies or photon pair generation rates even under harsh environmental conditions, e.g. when operated in the field. In this…

Implementations of many quantum communication protocols require sources of photon pairs. However, optimization of the properties of these photons for specific applications is an open problem. We theoretically demonstrate the possibility of…

Quantum Physics · Physics 2018-12-11 Mikołaj Lasota , Piotr Kolenderski

The process of spontaneous parametric down-conversion (SPDC) in nonlinear crystals makes it fairly easy to generate entangled photon states. It has been known for some time that the conversion efficiency can be improved by employing…

Quantum Physics · Physics 2017-08-23 Jonas Soderholm , Keiichi Hirano , Shigehiko Mori , Shuichiro Inoue , Sunao Kurimura

Spontaneous parametric down conversion (SPDC) has proven to be a robust and prominent method for creating non-classical light sources of entangled single-photon pairs. However, such sources suffer from low efficiency due to the inherent…

Optics · Physics 2025-08-27 Sky Semone , Matthew J. Brandsema , Christos Argyropoulos

Generation of entangled photons through spontaneous parametric down-conversion (SPDC) from ultrasmall sources like thin films, metasurfaces, or nanoantennas, offers unprecedented freedom in quantum state engineering. However, as the source…

Quantum Physics · Physics 2024-02-28 Vitaliy Sultanov , Maria Chekhova

Entangled photon-pairs are a critical resource in quantum communication protocols ranging from quantum key distribution to teleportation. The current workhorse technique for producing photon-pairs is via spontaneous parametric down…

Partially spatially coherent qubits are more immune to turbulent atmospheric conditions than coherent qubits, which makes them excellent candidates for free-space quantum communication. In this article, we report the generation of partially…

Quantum Physics · Physics 2023-07-26 Preeti Sharma , Sakshi Rao , Bhaskar Kanseri

The future of quantum photonic technology depends on the realization of efficient sources of single photons, the ideal carriers of quantum information. Parametric downconversion (PDC) is a promising route to create highly coherent,…

Photons generated by spontaneous parametric down conversion (SPDC) are one of the most useful resources in quantum information science. Two of their most important characteristics are the purity and the indistinguishability, which determine…

Quantum Physics · Physics 2013-02-28 C. I. Osorio , N. Sangouard , R. T. Thew

Photon modes have an important role in characterizing the quantum sources of light. Proper coupling of various photon modes obtained in spontaneous parametric down conversion (SPDC) process in optical fibers is essential to generate an…

Quantum Physics · Physics 2016-03-03 Ali Anwar , Chithrabhanu P , Salla Gangi Reddy , Nijil Lal , R. P. Singh