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A novel integrated optical source capable of emitting faint pulses with different polarization states and with different intensity levels at 100 MHz has been developed. The source relies on a single laser diode followed by four…

The linear constraint of secret key rate capacity is overcome by the tiwn-field quantum key distribution (QKD). However, the complex phase-locking and phase-tracking technique requirements throttle the real-life applications of twin-field…

Quantum Physics · Physics 2023-08-09 Jun-Lin Bai , Yuan-Mei Xie , Yao Fu , Hua-Lei Yin , Zeng-Bing Chen

Deterministic sources of high-fidelity entangled qubit pairs encoded in the dual-rail photonic basis, i.e., presence of a single photon in one of two orthogonal modes, are a key enabling technology of many applications of quantum…

Quantum Physics · Physics 2022-03-31 Prajit Dhara , Spencer J. Johnson , Christos N. Gagatsos , Paul G. Kwiat , Saikat Guha

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…

We present a theoretical and experimental investigation of the emission characteristics and the flux of photon pairs generated by spontaneous parametric downconversion in quasi-phase matched bulk crystals for the use in quantum…

Quantum Physics · Physics 2007-05-23 Daniel Ljunggren , Maria Tengner

Integrated photonics has recently become a leading platform for the realization and processing of optical entangled quantum states in compact, robust and scalable chip formats with applications in long-distance quantum-secured…

We demonstrate a polarization-entangled photon-pair source obtained via a type-II non-collinear quasi-phase-matched spontaneous parametric down-conversion process with a 10-mm periodically poled KTiOPO$_4$ crystal, which is as stable and…

Quantum Physics · Physics 2016-04-20 Sang Min Lee , Heonoh Kim , Myoungsik Cha , Han Seb Moon

Quantum key distribution (QKD) is a cryptographic protocol to enable two parties to share a secure key string, which can be used in one-time pad cryptosystem. There has been an ongoing surge of interest in implementing long-haul…

Quantum Physics · Physics 2022-08-22 Sourav Chatterjee , Kaumudibikash Goswami , Rishab Chatterjee , Urbasi Sinha

Chip-integrated photon-pair sources based on spontaneous parametric down-conversion (SPDC) have emerged as a promising solution for scalable quantum light generation. Thin-film lithium tantalate (TFLT) is a compelling $\chi^{(2)}$ platform,…

Optics · Physics 2026-05-26 Sakthi Sanjeev Mohanraj , Xiaodong Shi , Ran Yang , Lin Zhou , Di Zhu

Miniaturised entangled photon sources are highly demanded for the development of integrated quantum photonics. Since the invention of subwavelength optical metasurfaces and their successes at replacing bulky optical components, the…

Here, we present a proof-of-principle high-dimensional quantum key distribution (QKD) protocol utilizing the position and momentum entanglement of photon pairs. The protocol exploits the fact that position and momentum form mutually…

Quantum Physics · Physics 2026-03-09 Lukas Scarfe , Yingwen Zhang , Ebrahim Karimi

Entangled photon sources (EPS), the major building block for a variety of quantum communication protocols, are commonly developed by utilizing the spontaneous parametric down-conversion (SPDC) in $\chi^{2}$ nonlinear bulk optical materials.…

Quantum Physics · Physics 2022-07-14 Sandeep Singh , Vimlesh Kumar , Anirban Ghosh , G. K. Samanata

The practical roll-out of quantum communication technologies in optical networks and the adoption of novel quantum applications demand the distribution of single or entangled photons. Flexibility and dynamicity are paramount for the…

Entangled photon-pair sources are at the core of quantum applications like quantum key distribution, sensing, and imaging. Operation in space-limited and adverse environments such as in satellite-based and mobile communication requires…

We report on a simple but highly efficient source of polarization-entangled photon pairs at non-degenerate wavelengths. The fully collinear configuration of the source enables very high coupling efficiency into a single optical mode and…

Quantum Physics · Physics 2009-11-13 Pavel Trojek , Harald Weinfurter

Entangled photon pairs are crucial resources for quantum information processing protocols. Via the process of spontaneous parametric down-conversion (SPDC), we can generate these photon pairs using bulk nonlinear crystals. Traditionally,…

Quantum Physics · Physics 2024-04-12 Zi-Qi Zeng , Shi-Xin You , Zi-Xiang Yang , Chenzhi Yuan , Chenglong You , Rui-Bo Jin

We present an ultrabright polarization-entangled photon source that is optimally coupled into single-mode fibers (SMFs). This study theoretically and experimentally examines the characteristics of spontaneous parametric down-conversion…

Quantum Physics · Physics 2024-09-25 Kyungdeuk Park , Jungmo Lee , Dong-Gil Im , Dongkyu Kim , Yong Sup Ihn

We demonstrate a novel scheme for femto-second pulsed spontaneous parametric down-conversion in periodically poled KTP crystals. Our scheme is based on a crossed crystal configuration with collinear quasi-phase-matching. The non-degenerate…

Quantum key distribution (QKD) has convincingly been proven compatible with real life applications. Its wide-scale deployment in optical networks will benefit from an optical platform that allows miniature devices capable of encoding the…

Direct spectral characterization of a quantum photon-pair source usually involves cumbersome, costly, and time-consuming detection issues. In this study, we experimentally characterize the spectral properties of a type-II phase-matched…