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Quantum Technology: Driving Commercialisation of an Enabling Science

Generation and characterization of two-photon entanglement in the mid infrared

Adetunmise C. Dada, Taylor Shields, Shashi Prabhakar, Mehdi Haji Ebrahim, Gregor G. Taylor, D. Morozov, Kleanthis Erotokritou, Shigehito Miki, Masahiro Yabuno, Hirotaka Terai, Corin B. E. Gawith, Michael Kues, Lucia Caspani, Robert H. Hadfield, Matteo Clerici

Published Oct 6, 2021• 0 citations
Publisher

Abstract

We demonstrate two-photon interference and polarization entanglement at 2090 nm, constituting a crucial leap towards free-space mid-infrared quantum communication systems in a spectral region with high atmospheric transparency and reduced solar background.
DOI
10.1117/12.2598998

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Quantum-enhanced optical technologies operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. Currently, sources of entangled photons are available at visible, near-infrared and telecom wavelengths but are strongly underdeveloped at longer wavelengths. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-μm mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.
Quantum-enhanced optical systems operating within the 2- to 2.5-μm spectral region have the potential to revolutionize emerging applications in communications, sensing, and metrology. However, to date, sources of entangled photons have been realized mainly in the near-infrared 700- to 1550-nm spectral window. Here, using custom-designed lithium niobate crystals for spontaneous parametric down-conversion and tailored superconducting nanowire single-photon detectors, we demonstrate two-photon interference and polarization-entangled photon pairs at 2090 nm. These results open the 2- to 2.5-μm mid-infrared window for the development of optical quantum technologies such as quantum key distribution in next-generation mid-infrared fiber communication systems and future Earth-to-satellite communications.
Photon entanglement is essential for quantum communication, sensing, and computing. While research on frequency-degenerate entangled photons in the near-infrared (NIR) region has advanced significantly, entangled light spanning mid-infrared (MIR) and visible (VIS) frequencies remains under development [1]. For instance, in the MIR region, chiral collective lattice vibration modes that exhibit selectivity for circularly polarized light have been observed in two-dimensional layered materials [2], suggesting the existence of quantum entanglement with electronic states [3]. This entanglement could lead to the conservation of quantum states. For this purpose, it is necessary to generate quantum entangled states of photons in the MIR and VIS regions with high fidelity.
Given the important advantages of the mid-infrared optical range (2.5 to 25 μm) for biomedical sensing, optical communications, and molecular spectroscopy, extending quantum information technology to this region is highly attractive. However, the development of mid-infrared quantum information technology is still in its infancy. Here, we report on the generation of a time-energy entangled photon pair in the mid-infrared wavelength band. By using frequency upconversion detection technology, we observe the two-photon Hong-Ou-Mandel interference and demonstrate the time-energy entanglement between twin photons at 3082 nm via the Franson-type interferometer, verifying the indistinguishability and nonlocality of the photons. This work is very promising for future applications of optical quantum technology in the mid-infrared band, which will bring more opportunities in the fields of quantum communication, precision sensing, and imaging.