Recent advances on integrated quantum communications

Abstract

In recent years, the use of integrated technologies for applications in the field of quantum information processing and communications has made great progress. The resulting devices feature valuable characteristics such as scalability, reproducibility, low cost and interconnectivity, and have the potential to revolutionize our computation and communication practices in the future, much in the way that electronic integrated circuits have drastically transformed our information processing capacities since the last century. Among the multiple applications of integrated quantum technologies, this review will focus on typical components of quantum communication systems and on overall integrated system operation characteristics. We are interested in particular in the use of photonic integration platforms for developing devices necessary in quantum communications, including sources, detectors and both passive and active optical elements. We also illustrate the challenges associated with performing quantum communications on chip, by using the case study of quantum key distribution -the most advanced application of quantum information science. We conclude with promising perspectives in this field. Recent advances on integrated quantum communicationsRecent advances on integrated quantum communications 3 various important features, including for example the necessity to use foundry services and compatibility with mass manufacturing processes, the ability to support nonlinear and electro-optic effects and single-photon detection, the compatibility with specific encodings of quantum information, such as polarization, path, and time bins, and the adaptivity to a practical communication network infrastructure. The prevailing platforms for such applications can be described as follows:• Silicon-based platforms [3], which include silicon (Si) as well as silicon nitride (SiN) and silicon carbide (SiC), provide popular solutions as they combine several appealing characteristics. The global prevalence of the Si integration platform for electronics applications has ensured that all the physical and technological attributes of this platform have been fully examined. The existing silicon-based CMOS (Complementary Metal-Oxide-Semiconductor) wafer fabrication facilities open up vast possibilities for cost-effective solutions featuring high yield and reproducibility. Indeed, silicon-on-insulator (SOI) photonics has become a key technology for applications in telecommunications, optical interconnects, medical screening, spectroscopy, biology and chemical sensing, which were inconceivable a few years ago. This technology offers in general waveguides with a very high refractive index, allowing for an increased circuit compactness even for complex layouts involving many elements. Additionally, the high electric field intensity resulting from the extreme mode confinement is beneficial for nonlinear effects. These favorable characteristics, however, come at the expense of poor mode-matching with optical fibers, which is the privileged channel f...

Fabrication limits of waveguides in nonlinear crystals and their impact on quantum optics applications

“…classical single-and multiple-channel frequency conversion [1,2], optical parametric amplification [3], generation of squeezed states and entangled photons [4][5][6], frequency conversion for single-photon detection [7][8][9] and to interface single photons with quantum memories [10][11][12]. Realizing nonlinear processes in integrated waveguides is fundamental in bringing quantum protocols and devices closer to every-day life [13]. Integrated nonlinear waveguides offer a few advantages over bulk nonlinear crystals, since they achieve a stronger nonlinear interaction by increasing the field confinement over longer lengths and can be interfaced more easily with fibre networks [14].…”

Waveguide Cavity Resonator as a Source of Optical Squeezing

“…Integrated devices, boasting many of these properties, have made substantial improvements in recent years [6,7]. Devices have recently been constructed that combine state generation and manipulation in a single chip [8,9].…”

Indistinguishable Photons from Deterministically Integrated Single Quantum Dots in Heterogeneous GaAs/Si3N4 Quantum Photonic Circuits

“…The data was fitted with a two-sided exponential decay function convolved with a Gaussian that represented the experimental timing resolution, using a Poissonian statistics maximum likelihood estimator [42] (see Supplementary Material). Without any corrections, we obtain a conservative estimate of g (2) the WG examined here. We note that the simulated QD to GaAs WG coupling efficiency is ≈ 42 % for one propagation direction, and the overall coupling efficiency can potentially be significantly increased, by improving the fiber-to-Si 3 N 4 waveguide coupling, the adiabatic mode transformer design, and introduction of a high reflectivity mirror on the back port of the GaAs waveguide [17].…”

“…Detection coincidences with time delay τ were tracked with a 64 ps bin size. The normalized autocorrelation curve g (2) (τ ) is depicted in Fig. 3 d).…”