We deposit thin titanium-nitride (TiN) and TiN/Ti/TiN multilayer films on sapphire substrates and measure the reflectance and transmittance in the wavelength range from 400 nm to 2000 nm using a spectrophotometer. The optical constants (complex refractive indices), including the refractive index n and the extinction coefficient k, have been derived. With the extracted refractive indices, we propose an optical stack structure using low-loss amorphous Si (a-Si) anti-reflective coating and a backside aluminum (Al) reflecting mirror, which can in theory achieve 100% photon absorption at 1550 nm. The proposed optical design shows great promise in enhancing the optical efficiency of TiN-based microwave kinetic inductance photon-number-resolving detectors.Keywords optical constants, refractive index, TiN, microwave kinetic inductance detectors
IntroductionPhoton-number-resolving (PNR) detectors are able to directly measure the photon number and energy in a pulse of incident light. In particular, the PNR detectors at visible and nearinfrared wavelengths have important applications in many fields such as quantum secure communications [1], linear optics quantum computing [2], quantum optics experiments [3] and optical quantum metrology [4]. To meet the requirements of these applications, an ideal PNR detector should have both high energy resolution and high system detection efficiency. By minimizing the fiber-to-detector coupling losses and using optical stack structures that enhance the photon absorption by the absorber material, transition edge sensors (TESs) have demonstrated high energy resolution and near unity system detection efficiency at nearinfrared wavelengths [5,6,7,8,9,10,11].Another type of superconducting detector with intrinsic photon-number-resolving and energy-resolving capability is the microwave kinetic inductance detector (MKID) [12]. As
Abstract. Regularized arrangement of primitives on building façades to aligned locations and consistent sizes is important towards structured reconstruction of urban environment. Mixed integer linear programing was used to solve the problem, however, it is extremely time consuming even for state-of-the-art commercial solvers. Aiming to alleviate this issue, we cast the problem into binary integer programming, which omits the requirements for real value parameters and is more efficient to be solved. Firstly, the bounding boxes of the primitives are detected using the YOLOv3 architecture in real-time. Secondly, the coordinates of the upper left corners and the sizes of the bounding boxes are automatically clustered in a binary integer programming optimization, which jointly considers the geometric fitness, regularity and additional constraints; this step does not require a priori knowledge, such as the number of clusters or pre-defined grammars. Finally, the regularized bounding boxes can be directly used to guide the façade reconstruction in an interactive environment. Experimental evaluations have revealed that the accuracies for the extraction of primitives are above 0.82, which is sufficient for the following 3D reconstruction. The proposed approach only takes about 10% to 20% of the runtime than previous approach and reduces the diversity of the bounding boxes to about 20% to 50%.
Motivated by the recent experimental observations [M. Kataoka et al., Phys. Rev. Lett. 102, 156801 (2009)], we propose here an theoretical approach to implement quantum computation with bound states of electrons in moving quantum dots generated by the driving of surface acoustic waves. Differing from static quantum dots defined by a series of static electrodes above the two-dimensional electron gas (2DEG), here a single electron is captured from a 2DEG-reservoir by a surface acoustic wave (SAW) and then trapped in a moving quantum dot (MQD) transporting across a quasi-one dimensional channel (Q1DC), wherein all the electrons have been excluded out by the actions of the surface gates. The flying qubit introduced here is encoded by the two lowest adiabatic levels of the electron in the MQD, and the Rabi oscillation between these two levels could be implemented by applying finely-selected microwave pulses to the surface gates. By using the Coulomb interaction between the electrons in different moving quantum dots, we show that a desirable two-qubit operation, i.e., i-SWAP gate, could be realized. Readouts of the present flying qubits are also feasible with the current single-electron detected technique.
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