Entanglement is one of the key features of quantum information and communications technology. The method that has been used most frequently to generate highly entangled pairs of photons is parametric down-conversion. Short-wavelength entangled photons are desirable for generating further entanglement between three or four photons, but it is difficult to use parametric down-conversion to generate suitably energetic entangled photon pairs. One method that is expected to be applicable for the generation of such photons is resonant hyper-parametric scattering (RHPS): a pair of entangled photons is generated in a semiconductor via an electronically resonant third-order nonlinear optical process. Semiconductor-based sources of entangled photons would also be advantageous for practical quantum technologies, but attempts to generate entangled photons in semiconductors have not yet been successful. Here we report experimental evidence for the generation of ultraviolet entangled photon pairs by means of biexciton resonant RHPS in a single crystal of the semiconductor CuCl. We anticipate that our results will open the way to the generation of entangled photons by current injection, analogous to current-driven single photon sources.
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http://dx.doi.org/10.1038/nature02838 | DOI Listing |
npj Quantum Inf
December 2024
ETH Zurich, Department of Physics, Institute for Quantum Electronics, Optical Nanomaterial Group, Auguste-Piccard-Hof, 1, 8093 Zurich, Switzerland.
Optical quantum communication technologies are making the prospect of unconditionally secure and efficient information transfer a reality. The possibility of generating and reliably detecting quantum states of light, with the further need of increasing the private data-rate is where most research efforts are focusing. The physical concept of entanglement is a solution guaranteeing the highest degree of security in device-independent schemes, yet its implementation and preservation over long communication links is hard to achieve.
View Article and Find Full Text PDFLight Sci Appl
January 2025
Department of Electrical Engineering, California Institute of Technology, Pasadena, CA, 91125, USA.
Sensors are indispensable tools of modern life that are ubiquitously used in diverse settings ranging from smartphones and autonomous vehicles to the healthcare industry and space technology. By interfacing multiple sensors that collectively interact with the signal to be measured, one can go beyond the signal-to-noise ratios (SNR) attainable by the individual constituting elements. Such techniques have also been implemented in the quantum regime, where a linear increase in the SNR has been achieved via using entangled states.
View Article and Find Full Text PDFJ Am Chem Soc
December 2024
Department of Chemistry at Brown University, 324 Brook Street, Providence, Rhode Island 02912, United States.
Biomacromolecular networks with multiscale fibrillar structures are characterized by exceptional mechanical properties, making them attractive architectures for synthetic materials. However, there is a dearth of synthetic polymeric building blocks capable of forming similarly structured networks. Bottlebrush polymers (BBPs) are anisotropic graft polymers with the potential to mimic and replace biomacromolecules such as tropocollagen for the fabrication of synthetic fibrillar networks; however, a longstanding limitation of BBPs has been the lack of rigidity necessary to access the lyotropic ordering that underpins the formation of collagenous networks.
View Article and Find Full Text PDFJ Chem Theory Comput
December 2024
Max Planck Institute for the Structure and Dynamics of Matter, Luruper Ch 149, Hamburg 22761, Germany.
High-harmonic generation (HHG) is a nonlinear process in which a material sample is irradiated by intense laser pulses, causing the emission of high harmonics of incident light. HHG has historically been explained by theories employing a classical electromagnetic field, successfully capturing its spectral and temporal characteristics. However, recent research indicates that quantum-optical effects naturally exist or can be artificially induced in HHG, such as entanglement between emitted harmonics.
View Article and Find Full Text PDFPhilos Trans A Math Phys Eng Sci
December 2024
Department of Electrical and Electronic Engineering and H. H. Wills Physics Laboratory, QET Labs and Photonics and Quantum Group, University of Bristol, Bristol BS8 1UB, UK.
This paper presents a short history of the discovery by Rodney Loudon and Heidi Fearn of the counter-intuitive destructive interference effect occurring when two indistinguishable photons meet at a beamsplitter. This effect, commonly known as the Hong Ou Mandel effect, underpins much of present day photonic quantum information processing. Here I try to review its development from inception to present day proposals of million qubit photonic quantum computers.
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