A low-noise bipolar differential dc amplifier was studied at temperatures of 300 and 77 K. It was shown that to ensure the best amplifier performance in terms of noise figure when the operating temperature decreases from 300 to 77 K, it is advisable to use the transistor in the mode of low currents not exceeding 2 mA. It has been established that lowering the operating temperature to 77 K leads to a decrease in the input resistance of the amplifier from a value of several kiloohms to 100 Ohms, the dynamic range increases from 80 to 85 dB, and the harmonic coefficient increases from 0.09% to 1%. In addition, lowering the operating temperature to 77 K has a significant effect on the noise properties of the amplifier: the spectral density of voltage noise decreases from 1 to 0.4 nV/Hz1/2, the spectral density of current noise increases from 2.5 to 9 pA/Hz1/2, while also The threshold frequencies of 1/f noise increase: for voltage from (0.1...10) to 20 Hz and for current from (10...100) to 1000 Hz. The possibility of using an amplifier for low-temperature measurements of samples with low input resistance is substantiated.

The paper presents the electrical parameter measurements of commercially available surface mount device (SMD) resistors at cryogenic temperatures. Four types of resistors were investigated: Vishay FC0402, SMM0102, as well as Yageo RC0402 and Erkon-nn PI-160-0.05-1. The following parameters were measured: the nominal DC resistance, the frequency response of the resistance in the range from 20 Hz to 10kHz, and the scattering matrix in the frequency range from 10 MHz to 1 GHz. Measurements were conducted at three temperatures: 300 K, 77 K, and 4 K. The deviations of the nominal DC resistance values were obtained 1%, 0.6%, 35%, and 5.6% for FC0402, SMMO102, RC0402 and P1-160-0.05-1 resistors, respectively. These results align with the scattering matrix measurements for these resistors. Overall, the FC0402, P1-160-0.05-1, and SMM0102 series resistors are suitable for use in cryogenic electronic devices. However, using RC0402 resistors in cryogenic applications requires consideration of significant changes in their characteristics.

A survey of modern cryogenic electronics patents is the focus of this article. Modern patent databases such as PatSearch, Espacenet, and Orbit Questel were used to conduct an information search. Patent families related to cryogenic electronics over the past 20 years have been identified. The dynamics of patenting in this area is shown. The world leaders in the number of patents are revealed. The largest number of patents is registered in China. IBM holds the most patents in this field worldwide. Cryogenic electronics are the most dynamically developing industry. Modern commercially attractive solutions are associated with the development of a quantum computer. The development of wireless systems of qubit control and reading is the most relevant. It was found that there is no available information about the possibility of using an industrially produced electronic component base to create cryogenic electronics devices. Electronic components specially designed for cryogenic conditions are most often used, as a rule, using the superconductivity effect.

Cryogenic low-noise microwave amplifiers are an important tool in the measurement systems of various devices in the field of radio astronomy and quantum computing. The quality of measurements depends on its parameters - gain, equivalent noise temperature and power consumption. In the paper, we present a broadband low-noise cryogenic microwave amplifier operating in the frequency range of 1–3 GHz at an ambient temperature of 4 K. BFP840F heterostructural bipolar silicon germanium transistors were used as active elements. The design of the amplifier is a printed circuit board with lumped elements soldered on it. PCB packed in an aluminum case with input and output SMA connectors and a power connector. The measured parameters of the amplifier - the gain and the equivalent noise temperature at an ambient temperature of 4 K were more than 30 dB and less than 4 K, respectively. The power consumption of the amplifier was less than 8 mW.

The features of a direct current low noise amplifier designed on a commercial JFET transistor and operating at 77 K are investigated. The device design is the common-source transistor circuit with an auto-biased gate. We study the dependence of its characteristics on the amplifier operating current at a temperature of 77 K and compare it with the values of the same parameters at a temperature of 300 K. The following characteristics have been obtained: transfer function, input voltage and current noise densities. It has been shown that the voltage noise spectral density at 77 K has the same value (about 0.5 nV/Hz 1/2 ) as at room temperature at half the operating current. It points to the presence of the hot-electron effect in the transistor. The estimation of the current noise density is less than 6 fA/Hz 1/2 . The obtained results have shown the suitability of the JFET direct current low noise amplifier for cryogenic applications inside liquid nitrogen cooling systems.

We present experimental current-voltage, frequency response, and noise characteristics of modern low-noise silicon bipolar n-p-n (SSM2212) and p-n-p (SSM2220) transistors at cryogenic temperatures. We have measured the frequency response characteristics in the frequency range from 10 Hz to 102 kHz. The obtained results show that low temperature effects in semiconductor structures affect significantly the transistors' performance. In particular, we have observed a decrease of the collector current, a strong increase of the base current and a drop in the current gain. Also, the noise performances of transistors demonstrate the voltage noise reduction below 0.4 nV/Hz1/2@1 kHz for SSM2212 and below 0.3 nV/Hz1/2@1 kHz for SSM2220 at 77 K, but with the current noise being increased, reaching about 10 pA/Hz1/2@10 kHz. We show the possibility of using the bipolar transistors at cryogenic temperatures down to 50 K. This possibility is due to significant improvements in bipolar technology in recent years. We demonstrate the voltage gain of the common-emitter circuit is about of 30 at 48 K, indicating its suitability for use in cryogenic amplifiers.

In the paper DC low-noise amplifier based on commercial silicon SSM2212 transistors and operating at 77 K are described. The amplifier circuit is a differential stage with one of the arms grounded. Its characteristics, depending on the amplifier operating current, are measured. The schemes for measuring the main parameters of the amplifier are described and the following characteristics are obtained: transfer function, input voltage and current noise densities (less than 0.4 nV/H z 1/2 and about 5 pA/Hz1/2 at 10 kHz, respectively). For the voltage noise, the flicker noise threshold frequency is increased to 20 Hz at 77 K. Based on the results obtained, the amplifier input resistance and some parameters of the bipolar transistor hybrid-π noise model are estimated. In addition, the optimal resistance of the signal source is estimated to obtain the minimum noise figure. The obtained results have shown the suitability of commercially available bipolar transistors for cryogenic applications and could be used to optimize a custom readout system using a cryogenic amplifier based on this type of bipolar transistor.

The integration, scale-up, and multiplexing arrays of superconducting qubits in quantum circuits are the main challenges of superconducting quantum technology. Here we experimentally investigate the solid-state qubit multiplexing readout scheme, containing coplanar quarter-wavelength resonators coupled with a planar Xmon-type qubit, connected to a common coplanar transmission line. We find that the qubit energy spectrum is modified in the presence of an additional exciting signal at the fundamental frequency of the neighboring resonators. We attribute the origin of this effect to the electromagnetic field propagating through the common ground plane, which changes the qubit's characteristics. Our finding may be useful for the development of scalable superconducting quantum integrated circuits with arrays of multiplexed or coupled qubits for applications in superconducting quantum processing and computing.

We designed, implemented, and characterized differential amplifiers for cryogenic temperatures based on Si bipolar junction transistor technology. The amplifiers show high gain values of more than 60 dB at 300, 77, and 48 K. The minimum voltage noise spectral density was achieved at 77 K and corresponded to 0.33 nV/Hz0.5 with a flicker noise of 20 Hz. The maximum voltage gain was 70 dB at 77 K for a frequency range from DC to 17 kHz. We experimentally show that the parallel differential circuit design allows for a reduction of the voltage noise from 0.55 to 0.33 nV/Hz0.5 at 77 K.

A broadband low-noise four-stage high-electron-mobility transistor amplifier was designed and characterized in a cryogen-free dilution refrigerator at the 3.8 K temperature stage. The obtained power dissipation of the amplifier is below 20 mW. In the frequency range from 6 to 12 GHz its gain exceeds 30 dB. The equivalent noise temperature of the amplifier is below 6 K for the presented frequency range. The amplifier is applicable for any type of cryogenic microwave measurements. As an example we demonstrate here the characterization of the superconducting X-mon qubit coupled to an on-chip coplanar waveguide resonator.

We show an experimental study of superconducting X-mon qubit based on low noise wideband measurement setup. The setup includes wide stop-band low frequency filters with a stopband frequency up to 13 GHz, the broadband low-noise cryogenic microwave amplifier (cLNA) operating at 3.8 K. The obtained power dissipation of the cLNA is below 20 mW, the frequency operating ranges from 6 GHz to 12 GHz with a gain of 30 dB. The equivalent noise temperature of the amplifier is bellow 6 K for the presented frequency range. We demonstrate here the characterization of the superconducting X-mon qubit coupled to an on-chip coplanar waveguide resonator. We show standard qubit experiments: one and two-tones qubit spectroscopy, ac-Stark shift experiments for probing and excitation power sweeps.

The paper deals with silicon-germanium heterojunction transistor's operation under cryogenic conditions. Evaluating methodology was demonstrated with simple tool set. Families of output and input I-V characteristics in common emitter mode were measured at room and liquid nitrogen temperatures. Some cryogenic effects were observed and discussed, namely: 1) increasing of turn-on voltage due to freezing of major carriers in emitter with cooling, 2) enhancement of current gain due to bandgap difference of Si emitter and SiGe base even at LNT, 3) reducing of breakdown voltage due to more pronounced avalanche multiplication, 4) early voltage decreasing because of neutral base recombination, 5) improvement of power dissipation and reducing of self-heating effect. Despite of these effects, SiGe HBTs save their robust operation at cryogenic temperatures that confirms the capability of used IC technology process for LNT applications.

Microwave superconducting quantum circuits are strongly affected by various defects that are unavoidable during the production process. This paper presents a new method for measuring losses in an open transmission line. This line interacts through a capacitive coupling with a coplanar quarter-wavelength resonator, which is used to study losses therein. The authors have investigated the dependencies of losses on power and temperature (in the millikelvin range). It has been shown that major losses in a transmission line are due to the interaction of a microwave field with defects which are effectively described by two-level systems.

This work deals with investigation of CMOS operation at cryogenic conditions. Logic inverter made using 250 nm BCD technology process has been examined at 300, 77 and 48 K. Transfer and output static characteristics of CMOS inverter and characteristics of its transistors have been obtained and analyzed.

The properties of a superconducting flux quantum bit (qubit) in the quasidispersive mode, where the frequency of a probe signal is lower than the qubit excitation frequency but is close to it, have been experimentally studied. It has been shown that all parameters of the qubit inductively coupled to a coplanar resonator can be determined at the single-frequency excitation from the analysis of the frequency responses of the transmission of the probe signal at the output of this resonator. Under the additional excitation of the qubit by the signal at the second harmonic of the cavity, resonance dips have been observed because of resonance between the probe signal and induced Rabi splitting. It has been shown that the positions of these dips are in good agreement with the parameters of the qubit that are obtained by analyzing the amplitude–frequency response within the width of the fundamental resonance frequency.

Cообщается о результатах исследования сверхпроводникового потокового квантового бита (кубита) в квазидисперсионном режиме, когда частота пробного сигнала меньше, но тем не менее близка к частоте возбуждения кубита. В этом режиме, в отличие от известных экспериментов, взаимодействие кубита с волноводом приводит не только к смещению резонансной частоты, что характерно для дисперсионного режима, но также к заметному уширению резонансной линии, обусловленному спонтанным излучением кубита. Это позволяет на основе анализа амплитудно-частотной характеристики сигнала прохождения определить при одночастотном возбуждении характерные параметры кубита, индуктивно связанного с копланарным резонатором. Работа выполнена при финансовой поддержке Российского научного фонда в рамках проекта N 16-19-10069.

This paper reports on the results of the investigation of a superconducting flux quantum bit (qubit) in the quasi-dispersive regime, where the frequency of a probe signal even though is lower than, but, nevertheless, close to the excitation frequency of the qubit. In this regime, in contrast to the known experiments, the interaction of the qubit with a waveguide leads not only to a shift of the resonance frequency, which is characteristic of the dispersive regime, but also to a significant broadening of the resonance line due to the spontaneous emission of the qubit. On the basis of the analysis of the amplitude–frequency characteristic of the transmission signal, this makes it possible to determine, under single-frequency excitation, the characteristic parameters of the qubit inductively coupled to the coplanar resonator.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ СВОЙСТВ КРИОГЕННОГО МАЛОШУМЯЩЕГО SiGe УСИЛИТЕЛЯПРИ СУБКЕЛЬВИНОВЫХ ТЕМПЕРАТУРАХ Б

A low-noise cryogenic amplifier for the measurement of weak microwave signals at sub-Kelvin temperatures is constructed. The amplifier has five stages based on SiGe bipolar heterostructure transistors and has a gain factor of 35 dB in the frequency band from 100 MHz to 4 GHz at an operating temperature of 800 mK. The parameters of a superconducting quantum bit measured with this amplifier in the ultralow-power mode are presented as an application example. The amplitude–frequency response of the “supercon-ducting qubit–coplanar cavity” structure is demonstrated. The ground state of the qubit is characterized in the quasi-dispersive measurement mode.