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The flux qubit revisited to enhance coherence and reproducibility

Summary

The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). In this work, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad frequency tunability, strong anharmonicity, high reproducibility, and relaxation times in excess of 40 us at its flux-insensitive point. Qubit relaxation times 1 T across 22 qubits of widely varying designs are consistently matched with a single model involving resonator loss, ohmic charge noise, and 1/f flux noise, a noise source previously considered primarily in the context of dephasing, with temporal variation in 1 T attributed to quasiparticles. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, resulting in T2 ~ 85 us , approximately the 1 2T limit. In addition to realizing a dramatically improved flux qubit, our results uniquely identify photon shot noise as limiting 2 T in contemporary state-of-art qubits based on transverse qubit-resonator interaction.
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Summary

The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). In this work, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad frequency tunability, strong anharmonicity, high reproducibility, and relaxation times in excess of 40...

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Large enhancement of third-order nonlinear effects with a resonant all-dielectric metasurface

Published in:
AIP Adv., Vol. 6, No. 11, 1 November 2016, 115213.

Summary

A novel low-profile nonlinear metasurface, consisting of a single-layer of all-dielectric material, is proposed and numerically investigated by a nonlinear full-wave finite-difference time-domain (FDTD) method. The proposed metasurface is transparent for low, and opaque for high values of incident light intensity. The metasurface design is broadly applicable to enhancement of intrinsic nonlinearities of any material with a sufficiently high refractive index contrast. We illustrate the ability of this design to enhance intrinsic nonlinear absorption of a transition metal oxide, vanadium pentoxide (V2O5), with resonant metasurface elements. The complex third-order nonlinear susceptibility (x^(3)) for V2O5, representing both nonlinear refraction and absorption is considered in FDTD simulations. Our design achieves high initial transparency (>90%) for low incident light intensity. An order of magnitude decrease in the required input light intensity threshold for nonlinear response of the metasurface is observed in comparison with an unpatterend film. The proposed all-dielectric metasurface in this work is ultrathin and easy to fabricate. We envision a number of applications of this design for thin film coatings that offer protection against high-power laser radiation.
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Summary

A novel low-profile nonlinear metasurface, consisting of a single-layer of all-dielectric material, is proposed and numerically investigated by a nonlinear full-wave finite-difference time-domain (FDTD) method. The proposed metasurface is transparent for low, and opaque for high values of incident light intensity. The metasurface design is broadly applicable to enhancement of...

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Building low-power trustworthy systems: cyber-security considerations for real-time physiological status monitoring

Summary

Real-time monitoring of physiological data can reduce the likelihood of injury in noncombat military personnel and first-responders. MIT Lincoln Laboratory is developing a tactical Real-Time Physiological Status Monitoring (RT-PSM) system architecture and reference implementation named OBAN (Open Body Area Network), the purpose of which is to provide an open, government-owned framework for integrating multiple wearable sensors and applications. The OBAN implementation accepts data from various sensors enabling calculation of physiological strain information which may be used by squad leaders or medics to assess the team's health and enhance safety and effectiveness of mission execution. Security in terms of measurement integrity, confidentiality, and authenticity is an area of interest because OBAN system components exchange sensitive data in contested environments. In this paper, we analyze potential cyber-security threats and their associated risks to a generalized version of the OBAN architecture and identify directions for future research. The threat analysis is intended to inform the development of secure RT-PSM architectures and implementations.
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Summary

Real-time monitoring of physiological data can reduce the likelihood of injury in noncombat military personnel and first-responders. MIT Lincoln Laboratory is developing a tactical Real-Time Physiological Status Monitoring (RT-PSM) system architecture and reference implementation named OBAN (Open Body Area Network), the purpose of which is to provide an open, government-owned...

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Nonlinear equalization of microwave photonic links

Published in:
IEEE Int. Topical Meeting on Microwave Photonics, MWP 2016, 31 October - 3 November 2016.

Summary

High dynamic range is a key requirement in advanced microwave photonic systems. We demonstrate compensation of nonlinearities occurring in microwave photonic links using a novel digital nonlinear equalization technique and demonstrate suppression of distortion products by 33 dB with a small number of equalizer coefficients.
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Summary

High dynamic range is a key requirement in advanced microwave photonic systems. We demonstrate compensation of nonlinearities occurring in microwave photonic links using a novel digital nonlinear equalization technique and demonstrate suppression of distortion products by 33 dB with a small number of equalizer coefficients.

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Diode-pumped narrow linewidth multi-kW metalized Yb fiber amplifier

Published in:
Advanced Solid State Lasers, 30 October - 3 November 2016.

Summary

We investigate high brightness pumping of a multi-kW Yb fiber amplifier in a bi-directional pumping configuration. Each pump outputs 2 kW in a 200 um, 0.2 NA multi-mode fiber. Gold-coated specialty gain fibers, with 17 um MFD and 5-dB/meter pump absorption, have been developed. The maximum fiber amplifier output power is 3.1 kW, limited by multi-mode instability, with 90% O-O efficiency 12 GHz Linewidth and M2 < 1.15.
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Summary

We investigate high brightness pumping of a multi-kW Yb fiber amplifier in a bi-directional pumping configuration. Each pump outputs 2 kW in a 200 um, 0.2 NA multi-mode fiber. Gold-coated specialty gain fibers, with 17 um MFD and 5-dB/meter pump absorption, have been developed. The maximum fiber amplifier output power...

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A rotating source polarization measurement technique using two circularly polarized antennas

Published in:
38th Mtg. and Symp. of the Antenna Measurement Techniques Assoc., AMTA 2016, 30 October - 4 November 2016.

Summary

This paper combines the standard two-antenna gain measurement technique with the rotating source method for measuring the polarization ratio and tilt angle of the polarization ellipse of a circularly polarized antenna. The technique is illustrated with two identical helical antennas, one for the source and one for the antenna-under-test (AUT), facing each other. Measurements of the voltage transfer ratio are made over one 360 degree on-axis rotation of the source while the AUT remains stationary. The rotation causes the phase of the electric field of the principal polarization to rotate in one direction and the phase of the cross polarization to rotate in the opposite direction. A Discrete Fourier Transform (DFT) of the data from a single rotation is insufficient to resolve the two polarization components. Leakage from the principal polarization will most likely cover up the low-level opposite polarization signal. However, the DFT resolution can be artificially increased by appending to the measured data, precisely M-1 copies of the data. Now the polarization components will be separated by 2M revolutions. Application of a heavy weighting function to the augmented data and a phase compensation to the DFT allows a clear determination of the amplitude and phase of the on-axis principal and cross polarization components. The technique was verified by electromagnetic simulations and by measurements in an anechoic chamber with two 6-turn 5.8 GHz helical antennas separated by 4 feet. There was very good agreement between the simulations and measurements of the polarization ellipse tilt angle and a -20 dB polarization ratio.
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Summary

This paper combines the standard two-antenna gain measurement technique with the rotating source method for measuring the polarization ratio and tilt angle of the polarization ellipse of a circularly polarized antenna. The technique is illustrated with two identical helical antennas, one for the source and one for the antenna-under-test (AUT)...

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Writing your first paper: from code to research

Published in:
Grace Hopper Celebration of Women in Computing, 19-21 October 2016.

Summary

'Publish or perish,' once a term used to refer to the pressure placed on professors to publish their research has since expanded to apply to students and professionals in industry. There are numerous benefits to doing research and publishing the results, including personal satisfaction, career advancement, and prestige. In this session we will discuss how to begin doing research and write a first paper.
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Summary

'Publish or perish,' once a term used to refer to the pressure placed on professors to publish their research has since expanded to apply to students and professionals in industry. There are numerous benefits to doing research and publishing the results, including personal satisfaction, career advancement, and prestige. In this...

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3D printed conformal array antenna: simulations and measurements

Summary

A conformal array antenna has been investigated using a combination of 3D printer and copper plating techniques. Circular patch antenna elements were copper plated onto a 3D printed dielectric substrate made of ABS-M30 material. Measured and simulated element reflection coefficient, element gain patterns, and array scanned beam radiation patterns at L band are in good agreement.
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Summary

A conformal array antenna has been investigated using a combination of 3D printer and copper plating techniques. Circular patch antenna elements were copper plated onto a 3D printed dielectric substrate made of ABS-M30 material. Measured and simulated element reflection coefficient, element gain patterns, and array scanned beam radiation patterns at...

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Aperture PCB assemblies: transition to production ready designs

Published in:
6th Int. Symp. on Phased Array Systems and Technology, PAST 2016, 18-21 October 2016.

Summary

MACOM designed the initial radar panels for the next generation surveillance radar with limited funds, with the philosophy that the initial design would be kept as simple as possible and that incremental improvements would be made as the program progressed, with the intent of having a tile assembly that is easy to manufacture by the first build of a larger radar (approximately 80 panels). The design is now being updated for an 80 panel order with the goal of optimizing the design electrically, for assembly and for test. This paper will discuss both the design, assembly, packaging, and test updates that are being made to have a board and board assembly that is easy to manufacture and test, with the goal of keeping cost as low as possible. These techniques will not only be used for the MPAR tiles, but also for tiles that are currently being developed for other programs.
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Summary

MACOM designed the initial radar panels for the next generation surveillance radar with limited funds, with the philosophy that the initial design would be kept as simple as possible and that incremental improvements would be made as the program progressed, with the intent of having a tile assembly that is...

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Design and analysis of an axisymmetric phased array fed Gregorian reflector system for limited scanning

Author:
Published in:
6th Int. Symp. on Phased Array Systems and Technology, PAST 2016, 18-21 October 2016.

Summary

An axisymmetric phased array fed confocal parabolic Gregorian reflector system is explored. The antenna utilizes a planar phased array located near the vertex of the primary reflector. Numerical electromagnetic simulations based on the multilevel fast multipole method (MLFMM) were used to analyze and optimize the antenna parameters for limited scanning. Simulations of the scanning performance of a dual reflector system with a 2 meter diameter primary reflector operating at Ku band are presented.
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Summary

An axisymmetric phased array fed confocal parabolic Gregorian reflector system is explored. The antenna utilizes a planar phased array located near the vertex of the primary reflector. Numerical electromagnetic simulations based on the multilevel fast multipole method (MLFMM) were used to analyze and optimize the antenna parameters for limited scanning...

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