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In this paper the coherence and crossing symmetry of the electromagnetic interaction of photons involved in the spontaneous parametric down conversion (SPDC) phenomena in nonlinear crystals, are investigated. On this basis a new…

Quantum Physics · Physics 2008-10-23 D. B. Ion , P. Constantin , M. L. Ion

Besides many interesting application to the study of foundations of quantum mechanics, entangled state are now assuming a large relevance for some practical application. In particular, we discuss most recent results obtained in our…

Quantum Physics · Physics 2015-06-26 G. Brida , M. Genovese , C. Novero

In this work, we demonstrate the effect of self-splitting spatial quantum correlations induced by Gouy phase engineering. In the process of spontaneous parametric down conversion the pump beam is structured with a mode superposition that…

We report a controllable method for producing mixed two-photon states via Spontaneous Parametric Down-Conversion with a two-type-I crystal geometry. By using variable polarization rotators (VPRs), one obtains mixed states of various…

Quantum Physics · Physics 2015-10-16 Jibo Dai , Yink Loong Len , Yong Siah Teo , Leonid A. Krivitsky , Berthold-Georg Englert

In this article we investigate the orbital angular momentum spectrum of photons produced in parametric down conversion process. We study how the transverse profile of the pump mode affects the spectrum as compared to a gaussian pump beam.…

Quantum Physics · Physics 2019-05-08 Anindya Banerji , Ali Anwar , Hrushikesh Sable , Nijil Lal , Ravindra P. Singh

Versatile and high-brightness sources of high-dimensional entangled photon pairs are important for emerging quantum technologies such as secure quantum communication. Here, we experimentally demonstrate a new scalable method to create…

Quantum Physics · Physics 2020-10-28 Jaroslav Kysela , Manuel Erhard , Armin Hochrainer , Mario Krenn , Anton Zeilinger

The first direct measurement of photon bunching (g2 correlation function) in one output arm of a spontaneous-parametric-down-conversion source operated with a continuous pump laser in the single-photon regime is demonstrated. The result is…

A theory of spontaneous parametric down-conversion, which gives rise to a quantum state that is entangled in multiple parameters, such as three-dimensional wavevector and polarization, allows us to understand the unusual characteristics of…

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 present a source of polarization entangled photon pairs based on spontaneous parametric downconversion engineered for frequency uncorrelated telecom photon generation. Our source provides photon pairs that display, simultaneously, the…

We describe a scheme for the efficient generation of microwave photon pairs by parametric downconversion in a superconducting transmission line resonator coupled to a Cooper pair box serving as an artificial atom. By properly tuning the…

Mesoscale and Nanoscale Physics · Physics 2008-07-22 Florian Marquardt

In this paper, the crossing symmetry of the photons, from spontaneous parametric down conversion (SPDC) phenomena in nonlinear crystals, is used for the development of a new geometric optics based on quantum kinematic correlations. On this…

Optics · Physics 2008-10-21 D. B. Ion , P. Constantin , M. L. Ion

We describe a method to detect twin-beam multiphoton entanglement based on a beam splitter and weak nonlinearities. For the twin-beam four-photon entanglement, we explore a symmetry detector. It works not only for collecting two-pair…

Quantum Physics · Physics 2020-08-04 Yingqiu He , Dong Ding , Fengli Yan , Ting Gao

Entangled photon sources are crucial for quantum optics, quantum sensing and quantum communication. Semiconductor quantum dots generate on-demand entangled photon pairs via the biexciton-exciton cascade. However, the pair of photons are…

Quantum Physics · Physics 2019-07-09 Mohd Zeeshan , Nachiket Sherlekar , Arash Ahmadi , Robin L Williams , Michael E Reimer

Encoding continuous-variable quantum information in the optical domain has recently enabled the generation of large entangled states, yet robust implementation remains a challenge. Here, we present a straightforward protocol for generating…

Quantum Physics · Physics 2026-03-27 Sugar Singh Meena , David Barral , Ankan Das Roy , Sunita Meena , Amit Rai

The need for spatial and spectral filtering in the generation of polarization entanglement is eliminated by combining two coherently-driven type-II spontaneous parametric downconverters. The resulting ultrabright source emits photon pairs…

We introduce a scalable photonic platform that enables efficient generation of entangled photon pairs from a semiconductor quantum dot. Our system, which is based on a self-aligned quantum dot-micro-cavity structure, erases the need for…

The ability to generate quantum entangled photon pairs through spontaneous parametric down conversion (SPDC) is playing a pivotal role in many applications in quantum technologies, including quantum communications, quantum computation, and…

Optics · Physics 2025-06-24 Tongmiao Fan , Jihua Zhang , Andrey A. Sukhorukov

Pairs of entangled photons are crucial for photonic quantum technologies. The demand for integrability and multi-functionality suggests 'flat' platforms - ultrathin layers and metasurfaces - as sources of photon pairs. With the success in…

Optics · Physics 2026-02-02 Changjin Son , Maria Chekhova

Pairs of entangled photons are crucial for photonic quantum technologies. The demand for integrability and multi-functionality suggests 'flat' platforms - ultrathin layers and metasurfaces - as sources of photon pairs. Despite the success…