Unidirectional Microwave Transduction with Chirality Selected Short-Wavelength Magnon Excitations

Nonreciprocal magnon propagation has recently become a highly potential approach of developing chip-embedded microwave isolators for advanced information processing. However, it is challenging to achieve large nonreciprocity in miniaturized magnetic thin-film devices because of the difficulty of distinguishing propagating surface spin waves along the opposite directions when the film thickness is small. In this work, we experimentally realize unidirectional microwave transduction with sub-micron-wavelength propagating magnons in a yttrium iron garnet (YIG) thin film delay line. We achieve a non-decaying isolation of 30 dB with a broad field-tunable band-pass frequency range up to 14 GHz. The large isolation is due to the selection of chiral magnetostatic surface spin waves with the Oersted field generated from the coplanar waveguide antenna. Increasing the geometry ratio between the antenna width and YIG thickness drastically reduces the nonreciprocity and introduces additional magnon transmission bands. Our results pave the way for on-chip microwave isolation and tunable delay line with short-wavelength magnonic excitations.Comment: 6 pages, 4 figure

Anti-UVC Irradiation and Metal Chelation Properties of 6-Benzoyl-5,7-dihydroxy-4-phenyl-chromen-2-one: An Implications for Anti-Cataract Agent

Coumarin derivative 1, 5,7-dihydroxy-6-(3-methyl-1-butyryl)-4-phenyl-chromen- 2-one, has been reported to possess radical scavenging activity and DNA protection. We have synthesized a series of coumarins with structural modifications at positions C4, C5, C6 and C7 and evaluated them for their anti-UVC properties. Coumarin 7, 6-benzoyl-5,6-dihydroxy-4-phenyl-chromen-2-one, was found to have the most potent activity in protecting porcine γ-crystallin against UVC insults. Results of fluorescence assays indicated that compound 7 was capable of decreasing the loss of intensity while lens crystallins and DNA PUC19 were irradiated with UVC. Presence of compound 7 decreased hydroxyl radical levels determined by probe 1b and the free iron concentrations determined by Ferrozine reagent. The chelation assay showed that compound 7 was chelated to metal via 6-CO and 5-OH on the benzopyrone ring. The observed protective effects of compound 7 towards crystallins from insults of UVC and free radicals may be due to its iron-chelating activity and its peak absorption at 254 nm

Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network

Gravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects

Search for eccentric black hole coalescences during the third observing run of LIGO and Virgo

Despite the growing number of confident binary black hole coalescences observed through gravitational waves so far, the astrophysical origin of these binaries remains uncertain. Orbital eccentricity is one of the clearest tracers of binary formation channels. Identifying binary eccentricity, however, remains challenging due to the limited availability of gravitational waveforms that include effects of eccentricity. Here, we present observational results for a waveform-independent search sensitive to eccentric black hole coalescences, covering the third observing run (O3) of the LIGO and Virgo detectors. We identified no new high-significance candidates beyond those that were already identified with searches focusing on quasi-circular binaries. We determine the sensitivity of our search to high-mass (total mass M>70 M⊙) binaries covering eccentricities up to 0.3 at 15 Hz orbital frequency, and use this to compare model predictions to search results. Assuming all detections are indeed quasi-circular, for our fiducial population model, we place an upper limit for the merger rate density of high-mass binaries with eccentricities 0<e≤0.3 at 0.33 Gpc−3 yr−1 at 90\% confidence level

Ultralight vector dark matter search using data from the KAGRA O3GK run

Among the various candidates for dark matter (DM), ultralight vector DM can be probed by laser interferometric gravitational wave detectors through the measurement of oscillating length changes in the arm cavities. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here we present the result of a search for U(1)B−L gauge boson DM using the KAGRA data from auxiliary length channels during the first joint observation run together with GEO600. By applying our search pipeline, which takes into account the stochastic nature of ultralight DM, upper bounds on the coupling strength between the U(1)B−L gauge boson and ordinary matter are obtained for a range of DM masses. While our constraints are less stringent than those derived from previous experiments, this study demonstrates the applicability of our method to the lower-mass vector DM search, which is made difficult in this measurement by the short observation time compared to the auto-correlation time scale of DM

A Design of Hybrid ARQ Scheme using LDPC Code

Hybrid automatic repeat request (H-ARQ) scheme is an adaptive rate error control system that can adapt to changing channel condition in wireless communication systems. Hybrid ARQ system can achieve desired throughput efficiency and reliability for the data packet network that requires error free data transmission and is insensitive to transmission delay. The performance of hybrid ARQ depends on the error correcting capability of error correcting code and its retransmission mechanism. Low-density parity-check (LDPC) code is chosen as our error correcting code for its strong error correcting capability. This paper focuses on designing an intelligent retransmission mechanism. We proposed a retransmission mechanism called type-II hybrid data puncturing (DP) and diversity combining (DC) ARQ scheme. In high signal to noise ratio (SNR) situation, data puncturing is applied to enhance the system throughput. In low SNR situation, diversity combining is used to facilitate robust transmission. Our scheme combines the strength of both schemes. In comparison to rate-compatible (RC) type-II hybrid ARQ scheme, the proposed ARQ scheme operates on much higher code rate LDPC code for encoding and decoding. It has lower encoder and decoder complexity than rate-compatible (RC) type-II hybrid ARQ scheme. Because of its low hardware complexity and throughput performance, the proposed scheme is suitable for the modern high throughput mobile communication system.Table of Contents Acknowledgement iii Abstract iv List of Tables vi List of Figures vii Chapter 1 Introduction 1 1.1 Overview of Hybrid ARQ System 1 1.2 Related Work about Type-II Hybrid ARQ 3 1.3 Performance Measurement of an Automatic Repeat Request System 5 1.4 Thesis Organization 6 Chapter 2 Type-II Hybrid ARQ Schemes Using LDPC Code 7 2.1 Low Density Parity Check Code 7 2.1.1 Encoding of LDPC code 8 2.1.2 Tanner graph representation 8 2.1.3 Decoding of LDPC code 9 2.2 Rate-Compatible LDPC ARQ Scheme 10 2.2.1 Advantage and Disadvantage of RC-LDPC 11 2.3 Diversity Combining 12 2.4 Data Puncturing LDPC ARQ Scheme 12 2.4.1 Shorten 12 2.4.2 Data Puncturing LDPC ARQ Retransmission Mechanism 14 2.4.3 Advantage and Disadvantage of DP-LDPC ARQ 15 Chapter 3 Design of Hybrid ARQ Scheme Using LDPC Code 16 3.1 Comparison of RC-LDPC, DP-LDPC, and Diversity Combining 16 3.2 Hybrid Data Puncturing and Diversity Combining Scheme1 18 3.2.1 Techniques of Combining DP and DC 20 3.3 Hybrid Data Puncturing and Diversity Combining Scheme2 26 Chapter 4 Simulation Result and Comparison 31 4.1 Comparison of Hybrid DP+DC Scheme2, VVCR DP, DC 31 4.2 Performance of Hybrid DP+DC Scheme at Different Code Rate 34 4.3 Hardware Issue of Implementing Hybrid DP+DC Scheme 36 4.3.1 Functionality of Syndrome Test Unit 37 4.3.2 Syndrome Test Unit FPGA implementation 38 Chapter 5 Conclusion and Future Work 40 5.1 Conclusion 40 5.2 Future Work 40 Reference 4

Integrating Magnons for Quantum Information

Magnons, the quanta of collective spin excitations in magnetically ordered materials, have distinct properties that make them uniquely appealing for quantum information applications. They can have ultra-small wavelengths down to the nanometer scale even at microwave frequencies. They can provide coupling to a diverse set of other quantum excitations, and their inherently gyrotropic dynamics forms the basis for pronounced non-reciprocities. In this article we discuss what the current research challenges are for integrating magnetic materials into quantum information systems and provide a perspective on how to address them