A fully guided-wave squeezing experiment for fiber quantum networks

Abstract

We demonstrate, for the first time, the realization of an entirely guided-wave squeezing experiment at a telecom wavelength. The state generation relies on waveguide non-linear optics technology while squeezing collection and transmission are implemented by using only telecom fibre components. We observe up to −1.83 ± 0.05 dB of squeezing emitted at 1542 nm in CW pumping regime. The compactness and stability of the experiment, compared to free-space configurations, represent a significant step towards achieving out-of-the-lab CV quantum communication, fully compatible with existing telecom fibre networks. We believe that this work stands as a promising approach for real applications as well as for "do-it-yourself" experiments. PACS numbers:Generation and manipulation of continuous variable (CV) non-classical states of light are the object of intense research due to their importance in both fundamental and applied physics [1,2]. Among others, a valuable feature of CV quantum resources is that they can be generated in a deterministic way at the output of non-linear optical media [3]. Moreover, CV entanglement is affected but never vanishes completely for any level of external loss [4]. On these bases, CV quantum optics has experienced an increasing interest for its application to quantum key distribution (QKD) [5], with many proposals based on both single-mode [6-8] and two-mode squeezed light [9,10]. Entanglement distillation and entanglement swapping schemes for long distance quantum communication have been demonstrated [5,11] and systematic studies have been performed on the robustness of non-classicality against the communication channel losses [12,13]. A further step towards real-world applications of CV quantum communication has been done by generating squeezed light in the telecom C-band of wavelengths, where low-loss optical fibres and high performance standard components are available [14][15][16]. In the perspective of implementing quantum networks that exploit optical fibres to connect distant atomic quantum memories, a quantum interface has recently been developed, converting squeezed light from telecom to visible wavelengths compatible with suitable atomic transitions [17]. In the same spirit, a light-matter interface, coupling light guided in a tapered nanofibre to cold atoms, has been demonstrated [18].In this framework, and in order to comply with further out-of-the-lab realizations of CV quantum optics, we demonstrate, for the first time, the feasibility of a full guided-wave approach for both the generation and measurement of squeezed light at a telecom wavelength. In our scheme, single-mode squeezing at 1542 nm is generated by spontaneous parametric down conversion (SPDC) in a periodically poled lithium niobate ridge-waveguide (PPLN/RW). At the output of the PPLN/RW, the non-classical beam is measured with a fibre homodyne detector. This configuration allows implementing an extremely easy setup, entirely based on commercially available components, and fully compatible with existing fibre network...

Quantum photonics at telecom wavelengths based on lithium niobate waveguides

“…Very recently, in Nice, a entirely guided-wave realization of a squeezing experiment at telecom wavelength has been demonstrated, for the first time [237] (see Fig. 31).…”

Waveguide Cavity Resonator as a Source of Optical Squeezing

“…Pulsed systems are used for the intense peak powers, used to drive the nonlinear interaction, and this also helps to overcome the large losses that waveguide systems have traditionally exhibited. Only recently has a fully fibre integrated squeezed light source and detection scheme been demonstrated [21]. In other work, efficient and complicated manipulation of continuous-variable squeezing has been demonstrated in a silica-on-silicon chip [22] and generation of twin-beam squeezing has been demonstrated in both silicon nitride [23] and whispering gallery mode resonators [24].…”

Generation and Detection of Continuous Variable Quantum Vortex States via Compact Photonic Devices

“…This expression is obtained after applying Equation (24) on a generalization of Equation (23) to this case. Additionally, the situation of a click in the detector D 4 and no-click in D 3 could be also studied by only exchanging the subindices 3 and 4 in Equation (25). Likewise, another question should be borne in mind in our analysis: the dark counts.…”

“…In this regard, the implementation of CV-QIP in IO is taking its first steps. Demonstrations of on-chip squeezing up to −4.1 dB in the pulsed wave (PW) regime and −1.83 dB in the continuous wave (CW) regime have been reported [24,25], as well as the first demonstration of CV entanglement on-chip has been recently presented [26].…”