Scaling advantage of chaotic amplitude control for high-performance combinatorial optimization

The development of physical simulators, called Ising machines, that sample from low energy states of the Ising Hamiltonian has the potential to transform our ability to understand and control complex systems. However, most of the physical implementations of such machines have been based on a similar concept that is closely related to relaxational dynamics such as in simulated, mean-field, chaotic, and quantum annealing. Here we show that dynamics that includes a nonrelaxational component and is associated with a finite positive Gibbs entropy production rate can accelerate the sampling of low energy states compared to that of conventional methods. By implementing such dynamics on field programmable gate array, we show that the addition of nonrelaxational dynamics that we propose, called chaotic amplitude control, exhibits exponents of the scaling with problem size of the time to find optimal solutions and its variance that are smaller than those of relaxational schemes recently implemented on Ising machines.

Multifunctional metasurfaces integrating near-field display and 3D holography

Metasurfaces have versatile manipulation capabilities in the optical field and provide the possibility of building a compact optical device with various complex functions. They have been regarded as ideal candidates to construct a miniaturized optical system with high density and multi-channel information. In this work, reflective all-metallic multifunctional metasurfaces consisting of aluminum nanorods are designed by simultaneously realizing the near-filed display and three-dimensional (3D) holography. Specifically, in the proposed design, each nanorod acts as a complex amplitude modulator to provide continuous amplitude control and binary phase control. By carefully optimizing the orientations of nanorods, a multifunctional metasurface can be designed to display a near-field grayscale pattern and far-field 3D images simultaneously. Numerical results by a full-wave simulation validate the good performance of the proposed design. The proposed method could provide more degree of freedom to designs of lightweight devices, which could be employed in optical applications, such as the virtual or augmented reality display and anti-counterfeit technology.

Phase and Amplitude Control Integrated Circuit in 0.18 μm SiGe BiCMOS for Sub-6 GHz Phased Array Applications

This paper presents simulation results of the C-band transmit/receive (Tx/Rx) phased-arrays integrated circuit (IC) for sub-6 GHz communication links. It is based on 0.18 μm SiGe BiCMOS technology. Phase and amplitude control IC consists of one Tx/Rx channel. Digitally controlled phase shifter allows adjusting relative phase of the output microwave signal in the range from 0 to 360 degrees with 5.625 degree step (6-bit resolution). Digitally controlled active attenuator provides the transfer ratio adjusting in the range from 0 to –31 dB with 1 dB step (5 bit resolution). Amplitude and phase correction system based on integrated temperature sensor, auxiliary 4-bit phase shifter, 4-bit attenuator and digital control unit is implemented. Correction in –60—85 °C temperature range with 5-bit resolu-tion is provided. The root mean square (rms) phase adjustment error does not exceed 1.6 degree. The rms attenuation error does not exceed 0.37 dB. The noise figure in Rx mode is below 6.5 dB. The output power in Tx mode is above 6 dBm at P1dB. The power consumption is 375 mW and 525 mW in Rx and Tx modes respectively.

Isomorphic Circuits of Independent Amplitude Tunable Voltage-Mode Bandpass Filters and Quadrature Sinusoidal Oscillators

This paper presents isomorphic circuits of voltage-mode (VM) non-inverting bandpass filters (NBPFs) and VM quadrature sinusoidal oscillators (QSOs) with independent amplitude control functionality. The proposed VM NBPFs and VM QSOs exhibit low-output impedance and independent amplitude control, which are important for easily cascading the VM operation and independent control of the amplitude gain. The proposed isomorphic circuits employ three LT1228 commercial integrated circuits (ICs), two grounded capacitors, two grounded resistors and one floating resistor. The use of grounded capacitors is beneficial for the implementation of the IC. Both NBPFs have a high-input impedance and have a wide range of independent amplitude tunable passband gain without affecting the quality factor (Q) and center frequency (fo). The Q and fo parameters of the proposed NBPFs are orthogonal tunability. By feeding back each input signal to the output response of the NBPF, two VM fully uncoupled QSOs are also proposed. The proposed VM fully uncoupled QSOs have two quadrature sinusoidal waveforms with two low-output impedances and one independent amplitude tunable sinusoidal waveform. The frequency of oscillation (FO) and the condition of oscillation (CO) are fully uncoupled and controlled electronically. The performances of the proposed isomorphic circuits have been tested with a ±5 volt power supply and are demonstrated by experimental measurements which confirm the theoretical assumptions.

Reconfigurable Training, Vortex Writing and Spin-Wave Fingerprinting in an Artificial Spin-Vortex Ice

Strongly-interacting artificial spin systems are moving beyond mimicking naturally-occurring materials to find roles as versatile functional platforms, from reconfigurable magnonics to designer magnetic metamaterials. Typically artificial spin systems comprise nanomagnets with a single magnetisation texture: collinear macrospins or chiral vortices. By tuning nanoarray dimensions we achieve macrospin/vortex bistability and demonstrate a four-state metamaterial spin-system ‘Artificial Spin-Vortex Ice’ (ASVI). ASVI is capable of adopting Ising-like macrospins with strong ice-like vertex interactions, in addition to weakly-coupled vortices with low stray dipolar-field. The enhanced bi-texture microstate space gives rise to emergent physical memory phenomena, with ratchet-like vortex training and history-dependent nonlinear training dynamics. We observe vortex-domain formation alongside MFM tip vortex-writing. Tip-written vortices dramatically alter local reversal and memory dynamics. Vortices and macrospins exhibit starkly-differing spin-wave spectra with analogue-style mode-amplitude control via vortex training and mode-frequency shifts of ∆f = 3.8 GHz. We leverage spin-wave ‘spectral fingerprinting’ for rapid, scaleable readout of vortex and macrospin populations over complex training-protocols with applicability for functional magnonics and physical memory.

Amplitude Control Method of Magnetic Flux Vertical Modulation Structure for TMR Magnetic Sensor Based on Harmonic Component of Modulated Signal

Magnetic flux vertical modulation method based on piezoelectric resonance can reduce the 1/f noise of tunnel magnetoresistance (TMR) magnetic sensor and significantly improves the low-frequency magnetic field detectivity. However, the amplitude variation of the modulation structure will lead to the instability of the sensor output. In order to improve the amplitude stability of the modulation structure, an amplitude control method based on the amplitude ratio of the first and second harmonic components of the modulated signal was proposed. Compared with the piezoelectric or capacitive feedback method, this method does not require an independent amplitude conversion circuit, and has the advantages of simple structure, high control efficiency and strong anti-interference ability. The experimental results showed that the amplitude and temperature drift of the modulated structure was significantly suppressed, which is of great significance for enhancing the adaptability of the TMR magnetic sensor to the application environments.