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Generation and detection of polarization entanglement at 2.1 micron

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

Published Oct 29, 2020• 0 citations
OpenAlex

Abstract

Quantum-enhanced optical systems operating within the 2-2.5 µm spectral region have the potential to revolutionize emerging applications in communications, sensing and metrology. However, until now, sources of entangled photons have been realized mainly in the near-infrared 700-1550 nm spectral window. Above 2 µm lies an atmospheric transparency window with nearly one-third of the solar blackbody radiation as what is typical at telecom wavelengths. There is, therefore, a growing interest to deliver sources and detectors operating in this wavelength range for free-space optical communications and in emerging fields of high-sensitivity metrology, specifically, gravitational wave detection [1,2]. Here, using a 130 fs pulsed laser at wavelength 1.05 μm to pump custom-designed non-linear crystals for spontaneous parametric down-conversion (SPDC) process and tailored superconducting nanowire single-photon detectors (SNSPD), we demonstrate for the first-time two-photon quantum interference and polarization entanglement in the mid-infrared, at ≃ 2.1 μm.

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Quantum-enhanced optical systems operating within the 2-2.5 µm spectral region have the potential to revolutionize emerging applications in communications, sensing and metrology. However, until now, sources of entangled photons have been realized mainly in the near-infrared 700-1550 nm spectral window. Above 2 µm lies an atmospheric transparency window with nearly one-third of the solar blackbody radiation as what is typical at telecom wavelengths. There is, therefore, a growing interest to deliver sources and detectors operating in this wavelength range for free-space optical communications and in emerging fields of high-sensitivity metrology, specifically, gravitational wave detection [1,2]. Here, using a 130 fs pulsed laser at wavelength 1.05 μm to pump custom-designed non-linear crystals for spontaneous parametric down-conversion (SPDC) process and tailored superconducting nanowire single-photon detectors (SNSPD), we demonstrate for the first-time two-photon quantum interference and polarization entanglement in the mid-infrared, at ≃ 2.1 μm.
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.
Single-photon counting has become an essential tool in quantum optics experiments, as well as remote sensing and life science applications. However conventional technologies such as single-photon avalanche diodes, as well as the availability of standard telecom optical components, has limited much of this work to the near infrared/telecom wavelength range. Superconducting nanowire single photon detectors (SNSPDs) have emerged in recent years as the gold standard in photon counting applications due to their low dark count rates, fast timing resolution and high efficiency [1]. SNSPDs have also demonstrated photon counting efficiency out to much greater wavelengths which enables us to explore new experimental possibilities in the mid-infrared [2]. In this work we design and fabricate mid-infrared SNSPDs and deploy them in a variety of photon counting experiments [3,4]. The devices are based on a NbTiN superconducting film integrated into an optical cavity to enhance absorption in the mid-infrared. We characterise these devices using an optical parametric oscillator, tuneable between 1.5 m and 4.2 m. We then deploy these in a proof-of-principle tabletop light detection and ranging (LIDAR) experiment at 2.3 m. LIDAR in the mid-infrared is attractive due to spectral regions of low atmospheric absorption and reduced solar background photon flux, when compared to telecom wavelengths. We also present results from a photon-pair source operating at 2 m. This is a key resource for extending quantum optics and quantum secure communications to the mid infrared domain. Pairs are generated using a custom lithium niobate crystal and detected using SNSPDs. We demonstrate two-photon interference and polarisation entanglement of the photon pairs at 2 m. This work opens the pathway to future development of quantum optics and quantum technologies in the mid-infrared spectral region. References [1] Gol’tsman et al Applied Physics Letters 79 705 (2001) [2] Marisli et al Nano Letters 12 (9) 4799 (2012) [3] G. G. Taylor et al Optics Express 26 (27) 38147 (2018) [4] S. Prabhakar et al Science Advances 6 (13) eaay5195 (2019)
Quantum-optical technologies are transforming communication and metrology by enabling security and sensitivity beyond classical limits. Currently, these technologies are available at visible, near-infrared (NIR) and telecom wavelengths but are strongly underdeveloped at longer wavelengths. There is a growing demand for quantum sources operating in the 2 μm region for various applications. For example, such sources can enable daylight satellite-to-ground based quantum communications by taking advantage of an atmospheric transparency window with reduced solar blackbody radiation compared to telecom wavelengths [1,2,3]. Moreover, squeezed 2 μm sources are expected to have an impact on quantum metrology. For example, in gravitational wave detectors (eg. LIGO), such long wavelengths could reduce the quantum noise and scattering loss from crystalline silicon test masses [4]. Here, we report the generation and characterisation of a photon pair source at 2.080 μm with coincidence-to-accidental ratio (CAR) exceeding 10.
Extending single-photon detection capabilities into the mid- infrared is expected to have far-reaching implications for long-wavelength quantum optics, quantum and free-space communication, astronomy, environmental monitoring, and fundamental molecular sciences. We showcase the development of short-wave infrared (2.2-2.3 µm) and mid- wave infrared (3.0 µm) superconducting nanowire single-photon detectors (SNSPDs). In both wavelength ranges, we venture beyond state-of-the-art and achieve the best-reported system detection efficiencies and specific detectivity. We discuss the challenges in cryogenics, optics, and SNSPD design and use our mid-infrared single-photon detection to characterize emerging materials platforms and quantum emitters in a previously unattainable manner.
Extending single-photon detection capabilities into the mid- infrared is expected to have far-reaching implications for long-wavelength quantum optics, quantum and free-space communication, astronomy, environmental monitoring, and fundamental molecular sciences. We showcase the development of short-wave infrared (2.2-2.3 µm) and mid- wave infrared (3.0 µm) superconducting nanowire single-photon detectors (SNSPDs). In both wavelength ranges, we venture beyond state-of-the-art and achieve the best-reported system detection efficiencies and specific detectivity. We discuss the challenges in cryogenics, optics, and SNSPD design and use our mid-infrared single-photon detection to characterize emerging materials platforms and quantum emitters in a previously unattainable manner.