| In 1956,the cryotron was suggested by Dudley Buck,cryogenic superconducting device has experienced a rapid development,T-Flip Flop based on RSFQ(Rapid Single Flux Quantum)can be Operating up to 770 GHz.MIT designed and fabricated a superconducting nanowire logic device(nanowire cryotron,nTron)based on the cryotron and received extensive attentions in 2014.It has advantages like fast switching speed,low power consumption,driving ability,high gain,simple fabrication precess,and so on.Therefore,the nTron has immediate applications in classical and quantum communications,superconducting computer,and cryogenic readout circuit.The characteristics of nTron also indicate that it is a superconducting device with digital logic function,so it can be used to design complex digital circuits in large scale integration and its input-output characteristics are suitable for integration with existing superconducting technologies.This dissertation mainly focuses on superconducting nanowire logic device,studies the working mechanism of the nTron,optimizes the structure and fabricated process of the nTron,characterizes the multiple performance of the nTron,and applications in AND gate,OR gate,NOT gate.In addition,this paper also proposes a new structure of mulit-gate nTron,designs the nTron encoder using muti-gate nTrons and successfully reads out the SNSPD array.The main results are as follows:1.We realized to model the nTron using SPICE and simulated the curve of nTron’s input-output characterization.Built the experiment platform and measured the DC characteristics of nTron to provide guidance for use of the nTron.The experimental platform was built to test nTrons,and the experimental data verified the simulating results.The works provide an important theoretical direction and technical guarantee for the design and optimization of the nTron.2.This dissertation optimizes the structure and simplifies the fabricated process of the nTron.We designed the AND gate,OR gate,NOT gate based on nTron principle structure.For a 20 μA high and 5 ns wide input pulse,the timing jitter was 33.3 ps,while a typical SNSPD’s jitter was around 50 ps.the nTron had a total power dissipation of 19.7 n W and the gain of 23.9.The nTron was demonstrated to be operated at a clock frequency of 615.4 MHz,which was faster than the maximum counting rate of a typical SNSPD.The ntron can be triggered by a few μA high and nanoseconds wide input signal,showing the nTron was capable of reading an SNSPD pulse at the same signal level.For reading SNSPD or other detector arrays that demands less operation speed,our results suggest a digital circuit made from ntrons could be another promising alternative.3.This dissertation introduces a multi-gate superconducting nanowire cryotron,which functions as a 12-input OR gate within a footprint around 0.5 μm2.This paper desigens a superconducting digital encoder of ultra-low power dissipation and ultracompact size for cryogenic applications.Four cryotrons compose in a 4-bit encoder,which has a bias margin of 18.9%,an operation speed greater than 250 MHz,an average switching rms jitter of 75 ps,and a total power dissipation of only 361 n W.4.We designed an nTron amplifier using T-interface network and successfully amplified the signal which SNSPD responds to photons.To demonstrate nTron encoder’s function in a cryogenic system,we apply this encoder for multiplexing readout of a superconducting nanowire single photon detector array,whose pixel location is digitized into a 4-bit binary address with maintaining the time information of detected photons.By combing more nTron gates,a cryogenic digital circuit that can handle complex signal processing tasks can be made,such as a digital readout for a focal plane array of superconducting detectors. |
