scholarly journals Observation of frequency-uncorrelated photon pairs generated by counter-propagating spontaneous parametric down-conversion

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yi-Chen Liu ◽  
Dong-Jie Guo ◽  
Kun-Qian Ren ◽  
Ran Yang ◽  
Minghao Shang ◽  
...  

AbstractWe report the generation of frequency-uncorrelated photon pairs from counter-propagating spontaneous parametric down-conversion in a periodically-poled KTP waveguide. The joint spectral intensity of photon pairs is characterized by measuring the corresponding stimulated process, namely, the difference frequency generation process. The experimental result shows a clear uncorrelated joint spectrum, where the backward-propagating photon has a narrow bandwidth of 7.46 GHz and the forward-propagating one has a bandwidth of 0.23 THz like the pump light. The heralded single-photon purity estimated through Schmidt decomposition is as high as 0.996, showing a perspective for ultra-purity and narrow-band single-photon generation. Such unique feature results from the backward-wave quasi-phase-matching condition and does not has a strict limitation on the material and working wavelength, thus fascinating its application in photonic quantum technologies.

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Masayuki Hojo ◽  
Koichiro Tanaka

AbstractSpontaneous parametric down-conversion is an essential tool for a quantum light source in the infrared region ranging 2–5 µm for the purpose of material identification, chemical analysis, and gas sensing. So far, photon pairs from the process in a nonlinear crystal have low tunability and a narrow spectral range because of the phase-matching condition. Here, we propose a novel type of spontaneous parametric down-conversion processes that overcomes these challenges, where two photon pairs are simultaneously produced in the visible and infrared regions in periodically poled stoichiometric lithium tantalite. It allows broadband and tunable generation of infrared photon pairs that can be employed as an alternative light source for quantum infrared spectroscopy.


Nanoscale ◽  
2021 ◽  
Author(s):  
Boyuan Jin ◽  
Dhananjay Mishra ◽  
Christos Argyropoulos

Spontaneous parametric down-conversion (SPDC) is one of the most versatile nonlinear optical techniques for the generation of entangled and correlated single-photon pairs. However, it suffers from very poor efficiency leading...


2015 ◽  
Vol 13 (05) ◽  
pp. 1550032 ◽  
Author(s):  
X. Sánchez-Lozano ◽  
J. L. Lucio M.

We present a theoretical analysis of the process of spontaneous parametric down conversion (SPDC) in a nonlinear crystal characterized by a linearly-chirped χ(2) grating along the direction of propagation. Our analysis leads to an expression for the joint spectral amplitude, based on which we can derive various spectral–temporal properties of the photon pairs and of the heralded single photons obtained from the photon pairs, including: The single-photon spectrum (SPS), the chronocyclic Wigner function (CWF) and the Schmidt number. The simulations that we present are for the specific case of a collinear SPDC source based on a PPLN crystal with the signal and idler photons emitted close to the telecom window. We discuss the mechanism for spectral broadening due to the presence of a linearly chirped χ(2) grating, showing that not only the width but also to some extent the shape of the SPDC spectrum may be controlled. Also, we discuss how the fact that the different spectral components are emitted on different planes in the crystal leads to single-photon chirp.


2021 ◽  
Author(s):  
Bo-Yu Xu ◽  
Li-Kun Chen ◽  
Jintian Lin ◽  
Lan-Tian Feng ◽  
Rui Niu ◽  
...  

Abstract On-chip bright quantum sources with multiplexing ability are extremely high in demand for the integrated quantum networks with unprecedented scalability and complexity. Here, we demonstrate an ultrabright and broadband biphoton quantum source generated in a lithium niobate microresonator system. Without introducing the conventional domain poling, the on-chip microdisk produces entangled photon pairs covering a broad bandwidth promised by natural phase matching in spontaneous parametric down conversion. Experimentally, the multiplexed photon pairs are characterized by 30 nm bandwidth limited by the filtering system, which can be furthered enlarged. Meanwhile, the generation rate reaches 5.13 MHz/μW with a coincidence-to- accidental ratio up to 804. Besides, the quantum source manifests the prominent purity with heralded single photon correlation g(2)H(0)=0.0098±0.0021 and energy-time entanglement with excellent interference visibility of 96.5%±1.9%.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Byoung S. Ham

AbstractOver the last several decades, entangled photon pairs generated by spontaneous parametric down conversion processes in both second-order and third-order nonlinear optical materials have been intensively studied for various quantum features such as Bell inequality violation and anticorrelation. In an interferometric scheme, anticorrelation results from photon bunching based on randomness when entangled photon pairs coincidently impinge on a beam splitter. Compared with post-measurement-based probabilistic confirmation, a coherence version has been recently proposed using the wave nature of photons. Here, the origin of quantum features in a coupled interferometric scheme is investigated using pure coherence optics. In addition, a deterministic method of entangled photon-pair generation is proposed for on-demand coherence control of quantum processing.


2001 ◽  
Vol 56 (1-2) ◽  
pp. 178-181 ◽  
Author(s):  
Alberto Casado ◽  
Ramón Risco-Delgado ◽  
Emilio Santos

Abstract In this article we present a local hidden variables model for all experiments involving photon pairs produced in parametric down conversion, based on the Wigner representation of the radiation field. A modification of the standard quantum theory of detection is made in order to give a local realistic explanation of the counting rates in photodetectors. This model involves the existence of a real zeropoint field, such that the vacumm level of radiation lies below the threshold of the detectors.


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