Source and Channel Polarization over Finite Fields and Reed-Solomon Matrices

Polarization phenomenon over any finite field $\mathbb{F}_{q}$ with size $q$ being a power of a prime is considered. This problem is a generalization of the original proposal of channel polarization by Arikan for the binary field, as well as its extension to a prime field by Sasoglu, Telatar, and Arikan. In this paper, a necessary and sufficient condition of a matrix over a finite field $\mathbb{F}_q$ is shown under which any source and channel are polarized. Furthermore, the result of the speed of polarization for the binary alphabet obtained by Arikan and Telatar is generalized to arbitrary finite field. It is also shown that the asymptotic error probability of polar codes is improved by using the Reed-Solomon matrix, which can be regarded as a natural generalization of the $2\times 2$ binary matrix used in the original proposal by Arikan.Comment: 17 pages, 3 figures, accepted for publication in the IEEE Transactions on Information Theor

IPS Observation System for Miyun 50m Radio Telescope and Its Acceptance Observation

Ground-based observation of Interplanetary Scintillation(IPS) is an important approach of monitoring solar wind. A ground-based IPS observation system is newly implemented on 50m radio telescope, Miyun station, National Astronomical Observatories, Chinese Academy of Sciences(NAOC). This observation system is constructed for purpose of observing the solar wind speed and scintillation index by using the normalized cross-spectrum of simultaneous dual-frequency IPS measurement. The system consists of a universal dual-frequency front-end and a dual-channel multi-function back-end specially designed for IPS. After careful calibration and testing, IPS observations on source 3C273B and 3C279 are successfully carried out. The preliminary observation results show that this newly developed observation system is capable of doing IPS observation.The system sensitivity for IPS observation can reach over 0.3Jy in terms of IPS polarization correlator with 4MHz bandwidth and 2s integration time.Comment: 8 pages, 7 figure

Planet High Speed Radio: Crossing Gbps from a 3U CubeSat

Planet is a vertically integrated aerospace and data analytics company that operates the world\u27s largest commercial fleet of remote sensing satellites. Our mission is to image the whole world everyday, and make change visible, accessible, and actionable. We have launched over 350 satellites and built up an automated mission control and ground station infrastructure to monitor and control the satellites, and download the imagery data. Historically, small satellite radios have been downlink limited because of tight size, weight, and power (SWaP) constraints. Rapid prototyping, iteration, and adaptation of the latest commercial-o_-the-shelf (COTS) technology has allowed for continuous improvements in data throughput on our high speed radio from a very low-cost cubesat platform. In this talk, we will report on our latest X-band radio and antenna solution which has achieved a data rate over 1.6 Gbps from a 3U CubeSat on-orbit. Planet\u27s High Speed Downlink 2 (HSD2) is the latest generation compact, low-mass, and low-power radio that was built and deployed on 3U form-factor imaging CubeSats in December 2018. This system operates at X- band and is built using COTS parts with a dual polarization antenna. The two physical channels represent the two polarization modes, right hand circular polarization (RHCP) and left hand circular polarization (LHCP) and each physical channel utilizes 300 MHz of total bandwidth. Within each physical channel, there are three logical channels spaced 100 MHz apart center-to-center frequency. The individual channel symbol rate is 76.8 Msps. Each physical channel has 1 W RF output power and 15 dBi antenna gain. The total DC power consumption of the radio including the processor and the FPGA is 50Wand the total volume occupied by the radio and antenna, including the mechanical deployment structure for the antenna is 0.25U. The commercial digital television broadcasting standard DVB-S2 is used for modulation and coding. An adaptive coding and modulation (ACM) scheme is used to dynamically change the modulation and coding for each channel individually based on the available link margin. Our ground station network includes 15 dishes (29 dB/K gain-to-noise-temperature) across 5 sites located around the world. The HSD2 is capable of providing downlink volume of over 80 GB during a single ground station pass

All-optical switching of photonic entanglement

Future quantum optical networks will require the ability to route entangled photons at high speeds, with minimal loss and added in-band noise, and---most importantly---without disturbing the photons' quantum state. Here we present an all-optical switch which fulfills these requirements and characterize its performance at the single photon level. It exhibits a 200-ps switching window, 120:1 contrast, 1.5-dB loss, and induces no measurable degradation in the switched photons' entangled-state fidelity (< 0.002). As a proof-of-principle demonstration of its capability, we use the switch to demultiplex a single quantum channel from a dual-channel, time-division-multiplexed entangled photon stream. Furthermore, because this type of switch couples the temporal and spatial degrees of freedom, it provides an important new tool with which to encode multiple-qubit quantum states on a single photon

Properties and Construction of Polar Codes

Recently, Ar{\i}kan introduced the method of channel polarization on which one can construct efficient capacity-achieving codes, called polar codes, for any binary discrete memoryless channel. In the thesis, we show that decoding algorithm of polar codes, called successive cancellation decoding, can be regarded as belief propagation decoding, which has been used for decoding of low-density parity-check codes, on a tree graph. On the basis of the observation, we show an efficient construction method of polar codes using density evolution, which has been used for evaluation of the error probability of belief propagation decoding on a tree graph. We further show that channel polarization phenomenon and polar codes can be generalized to non-binary discrete memoryless channels. Asymptotic performances of non-binary polar codes, which use non-binary matrices called the Reed-Solomon matrices, are better than asymptotic performances of the best explicitly known binary polar code. We also find that the Reed-Solomon matrices are considered to be natural generalization of the original binary channel polarization introduced by Ar{\i}kan.Comment: Master thesis. The supervisor is Toshiyuki Tanaka. 24 pages, 3 figure

Metropolitan quantum key distribution with silicon photonics

Photonic integrated circuits (PICs) provide a compact and stable platform for quantum photonics. Here we demonstrate a silicon photonics quantum key distribution (QKD) transmitter in the first high-speed polarization-based QKD field tests. The systems reach composable secret key rates of 950 kbps in a local test (on a 103.6-m fiber with a total emulated loss of 9.2 dB) and 106 kbps in an intercity metropolitan test (on a 43-km fiber with 16.4 dB loss). Our results represent the highest secret key generation rate for polarization-based QKD experiments at a standard telecom wavelength and demonstrate PICs as a promising, scalable resource for future formation of metropolitan quantum-secure communications networks