This PDF file contains the front matter associated with SPIE Proceedings Volume 11027, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

In this paper, we review theoretical and experimental research progress on timing properties of superconducting nanowire single-photon detectors, including six possible mechanisms that induce timing jitter and experiments towards ultra-low timing jitter.

Superconducting nanowire single photon detectors (SNSPDs) have demonstrated advantages over traditional detectors in many fields [1]. Most fiber-coupled SNSPDs are coupled to single mode fibers, limiting their usability for applications where large surface area detectors are needed, for example fluorescence detection and satellite-based quantum communication [2][3]. Other important requirements for many applications are broadband detection efficiency, and low timing jitter [4]. So far, the increased meander length of multimode detectors, and the therefore increased kinetic inductance and number of imperfections due to film inhomogeneities have limited the timing jitter [5]. Moreover, combining low timing jitter with high detection efficiency and low dark count rate in one device is challenging due to the tradeoffs between different properties of SNSPDs [6]. In this paper, we achieved high efficiency and strong saturation over a broad wavelength range with a low timing jitter of 16.99 ps while maintaining a low dark count rate of < 0.2 Hz for an SNSPD coupled to a 50 µm core multimode fiber. To enhance the broadband absorption from 405 nm to 830 nm, detectors were fabricated on an optimized SiO2 cavity and Aluminum mirror. The geometry of the nanowire was also tuned to reach a good internal saturation of efficiency over the visible/NIR range but also to carry high current to get a large signal. Furthermore, a cryogenic readout amplifier was optimized to improve the signal to noise ratio and thus lead to high time resolution. Our devices can be readily used to enable higher resolution and faster quantum optics, bio-imaging, laser ranging and other optical experiments.

The accuracy of the measured distances in Satellite Laser Ranging is currently limited by 3 major error sources. These are associated with intensity variation of the detected echo, the satellite target structure and last but not least the electronic delay stability of the high resolution event timer. We have developed a continuous photon counting concept, where we can obtain accurate distances by timing the satellite return signals directly against a train of fs-clock pulses, derived from a delay compensated mode-locked laser. Conservative simulations suggest a practically achievable accuracy of less than 10 ps with respect to the time scale of the ranging station on the ground. In this contribution we outline the measurement concept and compare the obtained laboratory test results against the expectation of the theoretical simulations.

Ranging to the moon in the optical domain sets high demands on the tracking station. Apart from precise pointing and tracking with error tolerances of less than 1 second of arc, it also requires the capability for single photon event timing in the presence of significant background light levels. As a consequence of this technological challenge, there are only very few laser ranging stations like the McDonald Laser Ranging Station (MLRS) and the MeO station near Grasse in France that have successfully tracked the moon over the last almost 50 years. The Geodetic Observatory Wettzell is a fundamental station for Global Geodetic Observing System (GGOS) and therefore combines all the major measurement techniques of space geodesy collocated in one place. While the Wettzell Laser Ranging System (WLRS) has obtained a few observations of the Apollo 15 target in the past, the data volume was too sparse to make a significant contribution. Recent progress in the development of highly sensitive IR photon counting detectors has provided a new generation of diodes that offer high quantum efficiency at the fundamental wavelength of Nd:YAG at 1.064 μm and very short signal rise times at the same time. Furthermore they exhibit a very low intrinsic detector noise level. Together with a 75 mJ pulse energy and a laser pulse width as small as 10 ps, the WLRS has now repeatedly observed the Lunakhod 1 and the Apollo 15 target with a good signal to noise ratio, so that the remaining measurement error is limited to the effective reflector depth of the respective lunar targets in the presence of the libration of the moon. This talk outlines the station characteristics and discusses the detector performance for this high demanding application.

The new photon counting detector package has been developed for applications of the orbiting space debris optical tracking. The advanced construction of the detector control electronics enables to operate the detection chip in continuous and gated photon counting operational modes. Using the proposed construction the detector is capable to monitor the strength of a solar radiation diffused reflected by the space debris. Combining the continuous and gated detection modes enables to measure the photon flux rates over more than three orders of magnitudes ranging from one kHz to several MHz. In addition, the gated mode is optimized for laser ranging of orbiting space debris. The two operation modes of the detector may be switched electronically. The detector is based on a commercial SAP500 avalanche photodiode detection chip with active area diameter of 500 μm, which enables its simple integration into the large input aperture astronomical telescopes. The detection chip is operated at a fixed temperature of −8 °C. In a gated mode the photon detection efficiency exceeds 60% at 532 nm. Its timing resolution is typically better than 100 ps rms. In a continuous mode its dark count rate is well below 10 kHz. This detector package was developed as our contribution to the ESA activity “Space Situational Awareness program P2-SST-VII Expert Coordination Centre; Phase II”.

Time gating for SPADs is exploited either for increasing their maximum count rate or for detecting faint signals hidden by strong unwanted light pulses. Here we describe two short-gate techniques for high-speed photon counting with InGaAs/InP SPADs: i) a sinusoidal gating system at about 1.3 GHz, with very low afterpulsing and high count rate; ii) a SiGe integrated circuit for sub-nanosecond gating with < 200 ps rising/falling edges.

In the present time, the substantial advances in communication technology have prompted many challenges including secure transmission of sensitive information. Optical techniques have also been studied extensively for information security and validation. In this paper, we present a new optical information authentication techniques using photon counting in spiral phase transform (SPT) domain. SPT is used for the optical propagation. For SPT, a modified spiral phase function is utilized which defines the order of the transform. In the encryption process, an asymmetric approach is used, in which, first the input image is combined with the random phase mask and Fresnel propagated with a distance, d to get the intermediated image. Further, the polar decomposition (PD) is applied to the intermediate image which will give a rotational matrix and two symmetric matrices. The symmetric matrices can be used for authenticating the original information and serve as the private keys. The final encrypted image is obtained by performing the SPT of a particular order on the rotational matrix after PD. The encrypted image is made sparse by randomly retaining few pixels using photon counting approach. For authentication, the nonlinear correlation approach is studied, which offer better correlation peaks with fewer sparse-based complex samples. The numerical simulation results have been presented in support of the validity and effectiveness of the proposed technique. The proposed method deals with the optical encryption, authentication and also overcomes the limitations of data storage issue.

To verify the performance of Ghost Image via Sparsity Constraints (GISC) LiDAR system and evaluate the distance accuracy, on the basis of considering the parameters of the GISC LiDAR system, the research on design, development and setting method of related target is carried out. The measuring accuracy of distance measurement is verified in the field test. The measurement data of the airborne platform loading load are obtained to evaluate the range accuracy of the GISC LiDAR system.

Position-sensitive photon-counting virtual Frisch-grid CdZnTe (CZT) detectors provide an economical and robust design for high-efficiency gamma ray cameras for imaging and spectroscopy measurements. They can be used for a variety of applications including gamma-ray astronomy, medical and industrial imaging, environmental cleanup, nuclear safeguards and security. We present the first results from testing a 4x4 array module coupled to a front-end ASIC. Each detector in the array module operates as a mini time-projection chamber. For each gamma-ray event it provides 3D position information with high spatial- and high-spectral resolution. We employ learning algorithms based on extensive detector calibrations to reconstruct positional information and enhance the spectral resolution of the array. Also, the high-position resolution of the array allows for correcting the detectors’ response non-uniformities due to the presence of crystal defects. This allows the developers to use standard-grade (unselected) CZT crystals, while retaining good performance comparable to large-volume pixelated detectors.

Creating sufficiently strong entanglement between exciton-polaritons is a step of utmost importance towards the exploitation of these systems in quantum information processing with continuous variables. The generation of entanglement relies on the strength of the nonlinearity, which is weak for semiconductor microcavities. Recently, a way to essentially amplify the nonlinearity strength in these systems using two coherent laser fields was suggested, leading in theory to the creation of a fair amount of entanglement between exciton-polaritons in coupled cavities and networks in general. Throughout this process, the Josephson coupling and the enhanced nonlinearity in the two coupled cavities are held constant, with the former always larger. In this work we show that the entanglement generated with the above procedure can be substantially enhanced with the appropriate on-off switching of Josephson coupling between the cavities. Furthermore, we show that if we consider a time-dependent enhanced nonlinearity, through the modulation of the corresponding coherent laser fields, and allow it to attain larger values than the Josephson coupling, then we can generate larger values of entanglement using shortcuts to adiabaticity, a method developed to accelerate quantum adiabatic dynamics. The suggested methodologies are not restricted to exciton-polaritons but are expected to find applications in a wide spectrum of physical contexts, where nonlinear interacting bosons are encountered.

Atoms trapped in magic-wavelength optical tweezer will have the same light shift for the desired ground and excited states. In this case the position-dependence differential light shift of the desired transition can be eliminated. For cesium 6S_1/2 (Fg = 4, mF = +4) - 6P_3/2 (Fe = 5, mF = +5) cycling transition (852 nm), the magic wavelength was calculated theoretically for a linearly-polarized optical tweezer, and also it was verified experimentally to be 937.6 nm. We have demonstrated 852-nm triggered single-photon sources based on single cesium atom trapped in linearly-polarized optical tweezers implemented by using of 1064-nm and 937.6-nm lasers, respectively. The photon statistics were characterized by using of the Hanbury Brown - Twiss (HBT) scheme based on Si single-photon detectors (SSPDs). Strong anti-bunching effect [g^2(t=0) = 0.09] was recognized, and it shown perfectly the single-photon characters. The Hong-Ou-Mandel (HOM) two-photon interference measurements based on SSPDs were employed to evaluate the photon indistinguishability. Our preliminary experimental results indicated that the indistinguishability of single photons has been improved ~ 20% for the case of magic-wavelength optical tweezer. References: [1] Phys. Rev. A 94 (2016) 013409; [2] Appl. Phys. Express 9 (2016) 072702; [3] Opt. Express 25 (2017) p.15861

In this work the problem is solved to achieve high detection efficiency of TSPD for telecommunication systems. A fourlayer detection pixel of TSPD is proposed which consists of a photon absorber, thermoelectric sensor and the heat sink that also play the role of an electrical contact. The computer modeling was carried out using the equation for heat propagation from a limited volume and of the three-dimensional matrix method for differential equations. The results of computer simulation of heat propagation processes in the four-layer detection pixel of TSPD after the absorption of single photons with the 0.8 eV energy (λ = 1550 nm) are presented. Various geometries of the detection pixel consisting of lanthanum hexaboride nanoparticles as absorber material, the cerium hexaboride as a thermoelectric sensor and tungsten as electrical contact and heat sink are considered. It is shown that a TSPD with a four-layer detection pixel will have the gigahertz count rate and detection efficiency exceeding 90%. Taking into account the advantages of TSPD over the other types of detectors it can be argued that the four-layer detection pixel of the thermoelectric detector has strong prospects to solve a number of single-photon detection tasks.

The detection structure, it has been used in this experiment is employed for producing a single photon detector. The experiment was based on the analysis of changes in this low noise structure of a single photon detector in connection with its radiation damage in the event of neutron flux exposure. For the analysis of the radiation damaged structure was used the Zero Bias Thermally stimulated current method to explore the possibilities of filling traps with light sources. The filling of traps with photons emitted from LEDs or a flash device is compared on a neutron irradiated Si detector. The results of this experiment are used to increase the radiation hardness of manufactured single photon detection structures.

We consider a pair of coupled spins with Ising interaction in z-direction and study the problem of generating efficiently the triplet Bell state. We initially analyze the transitionless quantum driving shortcut to adiabaticity method and point out its limitations when the available duration approaches zero. In this short time limit we explicitly calculate the fidelity of the method and find it to be much lower than unity, no matter how large the available control fields become. We find that there is a lower bound on the necessary time to complete this transfer, set by the finite value of the interaction between the spins. We then use numerical optimal control to find bang-bang pulse sequences, as well as, smooth controls, which can generate high levels of the target Bell state in the minimum possible time. Finally, we explain how this method can be adapted for the efficient generation of general quantum entanglement in the system. The results of the present work are not restricted only to spin systems, but is expected to find also applications in other physical systems which can be modeled as interacting spins, such as, for example, coupled quantum dots.