Measurement and data-assisted simulation of bit error rate in RQL circuits

A circuit-simulation-based method is used to determine the thermally-induced bit error rate of superconducting Single Flux Quantum logic circuits. Simulations are used to evaluate the multidimensional Gaussian integral across noise current sources attached to the active devices. The method is data-assisted and has predictive power. Measurement determines the value of a single parameter, effective noise bandwidth, for each error mechanism. The errors in the distributed networks of comparator-free Reciprocal Quantum Logic nucleate across multiple Josephson junctions, so the effective critical current is about three times that of the individual devices. The effective noise bandwidth is only 6%–23% of the junction plasma frequency at a modest clock rate of 3.4 GHz, which is 1% of the plasma frequency. This analysis shows the ways measured bit error rate comes out so much lower than simplistic estimates based on isolated devices.

Light activation of 3D-printed structures: from millimeter to sub-micrometer scale

Three-dimensional (3D) printing enables the fabrication of complex, highly customizable structures, which are difficult to fabricate using conventional fabrication methods. Recently, the concept of four-dimensional (4D) printing has emerged, which adds active and responsive functions to 3D-printed structures. Deployable or adaptive structures with desired structural and functional changes can be fabricated using 4D printing; thus, 4D printing can be applied to actuators, soft robots, sensors, medical devices, and active and reconfigurable photonic devices. The shape of 3D-printed structures can be transformed in response to external stimuli, such as heat, light, electric and magnetic fields, and humidity. Light has unique advantages as a stimulus for active devices because it can remotely and selectively induce structural changes. There have been studies on the light activation of nanomaterial composites, but they were limited to rather simple planar structures. Recently, the light activation of 3D-printed complex structures has attracted increasing attention. However, there has been no comprehensive review of this emerging topic yet. In this paper, we present a comprehensive review of the light activation of 3D-printed structures. First, we introduce representative smart materials and general shape-changing mechanisms in 4D printing. Then, we focus on the design and recent demonstration of remote light activation, particularly detailing photothermal activations based on nanomaterial composites. We explain the light activation of 3D-printed structures from the millimeter to sub-micrometer scale.

Watt-Level Ka-Band Integrated Doherty Power Amplifiers: Technologies and Power Combination Strategies Invited Paper

This paper discusses some of the design choices underlying the development of watt-level integrated Doherty power amplifiers in the K and Ka band, focusing on compound semiconductor technologies. The key aspect of on-chip power combination is discussed, presenting and comparing some of the possible alternatives. Then, the impact on the achievable bandwidth and performance of different parameters is quantified, adopting an approximate analysis, which focuses on the Doherty output combiner and allows estimating the non-linear performance of the amplifier thanks to some simplifying assumptions, without requiring a full, non-linear model of the active devices. Two sample GaAs and GaN technologies are compared first, considering parameters that are representative of the currently available commercial processes, and then several power combination strategies are analyzed, adopting the GaN technology, which is currently the only one that allows achieving the power levels required by the applications directly on chip. Finally, some hints as to the impact of the output parasitic effects of the transistors on the presented analysis are given.

Adaptive Sliding Mode Control Vibrations of Structures

The sliding mode controller is one of the interesting classical nonlinear controllers in structural vibration control. From its apparition, in the middle of the twentieth century, this controller was a subject of several studies and investigations. This controller was widely used in the control of various semi-active or active devices in the civil engineering area. Nevertheless, the sliding mode controller offered a low sensitivity to the uncertainties or the system condition variations despite the presence of the Chattering defect. However, the adaptation law is one of the frequently used solutions to overcome this phenomenon offering the possibility to adapt the controller parameters according to the system variations and keeping the stability of the whole system assured. The chapter provides a sliding mode controller design reinforced by an adaptive law to control the desired state of an excited system. The performance of the adaptive controller is proved by numerical simulation results of a three-story excited structure.

Spectrometry of pulsed photon radiation

The energy distribution (spectrum) of pulsed photon radiation can hardly be measured using active devices, therefore, a thermoluminescence detector (TLD)-based few channel spectrometer is used in combination with a Bayesian data analysis to help resolve this problem. The spectrometer consists of 30 TLD layers interspaced by absorbers made of plastics and metals with increasing atomic numbers and thickness. Thus, the main idea behind the device is the deeper the radiation penetrates - the higher the radiation’s energy when the radiation impinges perpendicular to the front of the spectrometer. From the doses measured in the TLD layers and from further prior available information, the photon spectrum is deduced using a Bayesian data analysis leading to absolute spectra and doses including their uncertainties and coverage intervals. This spectrometer was successfully used in two different scenarios, i.e., for the spectrometry of the radiation field two different industrial type open beam pulsed X ray generators and secondly in three different radiation fields of a medical accelerator.

Enhanced gyrotropic birefringence and natural optical activity on electromagnon resonance in a helimagnet

Spontaneous symmetry breaking in crystalline solid often produces exotic nonreciprocal phenomena. As one such example, the unconventional optical rotation with nonreciprocity, which is termed gyrotropic birefringence, is expected to emerge from the magnetoelectric coupling. However, the fundamental nature of gyrotropic birefringence remains to be examined. Here w`e demonstrate the gyrotropic birefringence enhanced by the dynamical magnetoelectric coupling on the electrically active magnon resonance, i.e. electromagnon, in a multiferroic helimagnet. The helical spin order having both polarity and chirality is found to cause the giant gyrotropic birefringence in addition to the conventional gyrotropy, i.e. natural optical activity. It is demonstrated that the optical rotation of gyrotropic birefringence can be viewed as the nonreciprocal rotation of the optical principal axes, while the crystallographic and magnetic anisotropies are intact. The independent control of the nonreciprocal linear (gyrotropic birefringence) and circular (natural optical activity) birefringence/dichroism paves a way for the optically active devices.

Mass Dampers with Limited Amplitude

Mass dampers are widely used in engineering applications. We consider the effects of limitations on the damper amplitude. Using simple methods to analyze very general mass dampers, we find an upper limit to the damping. The maximum damping logarithmic decrement is δmax = 4μα, where μ is the mass ratio, and α isthe amplitude ratio of damper to structure amplitude. The result is further discussed in relation to Tuned Mass Dampers (TMDs), which can performvery well if there is enough avaliable space. In practice, amplitude limits always apply, and our result can be used to relate these to the damper performance.Our result also applies to active devices, which have to obey the limit mentioned above. Simulated tests of TMDs and other mass dampers are described. The damping is measured both by decay tests and by forced motion test. The methods agree well in the amplitude-limited regime. In other cases, decay tests are difficulet to interpret, indicating that one needs to be very careful whenmeasuring damping of 2DOF systems based solely on decay tests. We hope that our result may inform the selection and design of mass dampers in the future, where one should consider amplitude limits as the very first step.

Broadband Terahertz Photonic Integrated Circuit with Integrated Active Photonic Devices

Present-day photonic terahertz (100 GHz–10 THz) systems offer dynamic ranges beyond 100 dB and frequency coverage beyond 4 THz. They yet predominantly employ free-space Terahertz propagation, lacking integration depth and miniaturisation capabilities without sacrificing their extreme frequency coverage. In this work, we present a high resistivity silicon-on-insulator-based multimodal waveguide topology including active components (e.g., THz receivers) as well as passive components (couplers/splitters, bends, resonators) investigated over a frequency range of 0.5–1.6 THz. The waveguides have a single mode bandwidth between 0.5–0.75 THz; however, above 1 THz, these waveguides can be operated in the overmoded regime offering lower loss than commonly implemented hollow metal waveguides, operated in the fundamental mode. Supported by quartz and polyethylene substrates, the platform for Terahertz photonic integrated circuits (Tera-PICs) is mechanically stable and easily integrable. Additionally, we demonstrate several key components for Tera-PICs: low loss bends with radii ∼2 mm, a Vivaldi antenna-based efficient near-field coupling to active devices, a 3-dB splitter and a filter based on a whispering gallery mode resonator.

On the VCO/Frequency Divider Interface in Cryogenic CMOS PLL for Quantum Computing Applications

The availability of quantum microprocessors is mandatory, to efficiently run those quantum algorithms promising a radical leap forward in computation capability. Silicon-based nanostructured qubits appear today as a very interesting approach, because of their higher information density, longer coherence times, fast operation gates, and compatibility with the actual CMOS technology. In particular, thanks to their phase noise properties, the actual CMOS RFIC Phase-Locked Loops (PLL) and Phase-Locked Oscillators (PLO) are interesting circuits to synthesize control signals for spintronic qubits. In a quantum microprocessor, these circuits should operate close to the qubits, that is, at cryogenic temperatures. The lack of commercial cryogenic Design Kits (DK) may make the interface between the Voltage Controlled Oscillator (VCO) and the Frequency Divider (FD) a serious issue. Nevertheless, currently this issue has not been systematically addressed in the literature. The aim of the present paper is to investigate the VCO/FD interface when the temperature drops from room to cryogenic. To this purpose, physical models of electronics passive/active devices and equivalent circuits of VCO and the FD were developed at room and cryogenic temperatures. The modeling activity has led to design guidelines for the VCO/FD interface, useful in the absence of cryogenic DKs.