Ultra-Low-Power Superconductor Logic

We have developed a new superconducting digital technology, Reciprocal Quantum Logic, that uses AC power carried on a transmission line, which also serves as a clock. Using simple experiments we have demonstrated zero static power dissipation, thermally limited dynamic power dissipation, high clock stability, high operating margins and low BER. These features indicate that the technology is scalable to far more complex circuits at a significant level of integration. On the system level, Reciprocal Quantum Logic combines the high speed and low-power signal levels of Single-Flux- Quantum signals with the design methodology of CMOS, including low static power dissipation, low latency combinational logic, and efficient device count.Comment: 7 pages, 5 figure

Whispering Vortices

Experiments indicating the excitation of whispering gallery type electromagnetic modes by a vortex moving in an annular Josephson junction are reported. At relativistic velocities the Josephson vortex interacts with the modes of the superconducting stripline resonator giving rise to novel resonances on the current-voltage characteristic of the junction. The experimental data are in good agreement with analysis and numerical calculations based on the two-dimensional sine--Gordon model.Comment: 5 pages, 5 figures, text shortened to fit 4 pages, correction of typo

Observation of progressive motion of ac-driven solitons

We report the first experimental observation of phase-locked motion of a topological soliton at a nonzero average velocity in a periodically modulated lossy medium, under the action of an ac force with no dc component [the effect was predicted by G. Filatrella, B.A. Malomed, and R.D. Parmentier, Phys. Lett. A 198, 43 (1995)]. The velocity is related by a resonant condition to the driving frequency. The observation is made in terms of the current-voltage, I(V), characteristics for a fluxon trapped in an annular Josephson junction placed into dc magnetic field. Large zero-crossing constant-voltage steps, exactly corresponding to the resonantly locked soliton motion at different orders of the resonance, are found on the experimental I(V) curves. A measured dependence of the size of the steps vs. the external magnetic field is in good agreement with predictions of an analytical model based on the balance equation for the fluxon's energy. The effect has a potential application as a low-frequency voltage standard. The work was supported by a grant from the German-Israeli Foundation.Comment: Physical Review B, in press (Rapid Communication

Ferromagnetic Josephson switching device with high characteristic voltage

We develop a fast Magnetic Josephson Junction (MJJ) - a superconducting ferromagnetic device for a scalable high-density cryogenic memory compatible in speed and fabrication with energy-efficient Single Flux Quantum (SFQ) circuits. We present experimental results for Superconductor-Insulator-Ferromagnet-Superconductor (SIFS) MJJs with high characteristic voltage IcRn of >700 uV proving their applicability for superconducting circuits. By applying magnetic field pulses, the device can be switched between MJJ logic states. The MJJ IcRn product is only ~30% lower than that of conventional junction co-produced in the same process, allowing for integration of MJJ-based and SIS-based ultra-fast digital SFQ circuits operating at tens of gigahertz.Comment: 10 pages, 4 figure

RF assisted switching in magnetic Josephson junctions

We test the effect of an external RF field on the switching processes of magnetic Josephson junctions (MJJs) suitable for the realization of fast, scalable cryogenic memories compatible with Single Flux Quantum logic. We show that the combined application of microwaves and magnetic field pulses can improve the performances of the device, increasing the separation between the critical current levels corresponding to logical "0" and "1." The enhancement of the current level separation can be as high as 80% using an optimal set of parameters. We demonstrate that external RF fields can be used as an additional tool to manipulate the memory states, and we expect that this approach may lead to the development of new methods of selecting MJJs and manipulating their states in memory arrays for various applications

High Density Fabrication Process for Single Flux Quantum Circuits

We implemented, optimized and fully tested over multiple runs a superconducting Josephson junction fabrication process tailored for the integrated digital circuits that are used for control and readout of superconducting qubits operating at millikelvin temperatures. This process was optimized for highly energy efficient single flux quantum (ERSFQ) circuits with the critical currents reduced by factor of ~10 as compared to those operated at 4.2 K. Specifically, it implemented Josephson junctions with 10 uA unit critical current fabricated with a 10 uA/um2 critical current density. In order to circumvent the substantial size increase of the SFQ circuit inductors, we employed a NbN high kinetic inductance layer (HKIL) with a 8.5 pH/sq sheet inductance. Similarly, to maintain the small size of junction resistive shunts, we used a non-superconducting PdAu alloy with a 4.0 ohm/sq sheet resistance. For integration with quantum circuits in a multi-chip module, 5 and 10 um height bump processes were also optimized. To keep the fabrication process in check, we developed and thoroughly tested a comprehensive Process Control Monitor chip set.Comment: 10 pages, 5 figures, 1 tabl

Resonant flux motion and I-V -characteristics in frustrated Josephson junctions

We describe the dynamics of fluxons moving in a frustrated Josephson junction with p, d, and f-wave symmetry and calculate the I-V characteristics. The behavior of fluxons is quite distinct in the long and short length junction limit. For long junctions the intrinsic flux is bound at the center and the moving integer fluxon or antifluxon interacts with it only when it approaches the junction's center. For small junctions the intrinsic flux can move as a bunched type fluxon introducing additional steps in the I-V characteristics. Possible realization in quantum computation is presented.Comment: 21 pages, 8 figure

Влияние освещения на проращивание семян капусты китайской и брокколи и антиоксидантную активность микрозелени в закрытой системе синерготрона ИСР 1.01

Relevance. Growing plants in artificial conditions (closed agroecosystems) requires precise regulation of plant growth factors, starting from the first stages of ontogenesis. One of the parameters is the presence or absence of light in the period of seed germination. For most types of cabbage the standard method is germination in the dark, but for freshly harvested seeds (at rest) light exposure is necessary. According to the literature, the mechanisms of the effect of light on seed germination are complex and ambiguous, so the issue needs detailed research.Methods. Therefore, the purpose of this work was to study the germination of seeds of broccoli (Brassica oleracea var. italica Plenck) and Chinese cabbage (Brassica rapa var. chinensis), taking into account the light factor and the simultaneous analysis of antioxidant activity as a marker of changes in metabolic processes.Results. The experiment has revealed a significant increase in the antioxidant activity of the microgreens during germination in the dark compared to germination in the light (in broccoli by 5.5 times, in Chinese cabbage by 4.8 times). Later on, after the seedlings are moved to the light, the differences between the light and dark versions practically disappear. After germination in the light, the antioxidant activity of microgreens in comparison with the original (dry seeds) decreased by 3-3.5 times, while in the dark – on the contrary, increased by 1.5-1.6 times. The final results of germination (germination energy and seed germination) practically do not differ in the versions. In the case of dark germination, the height of microgreens is greater (due to etiolation and stretching in the absence of light), however, later on, the differences in the versions are smoothed out. The biomass of microgreens in the version of light germination on the 4th day after sowing seeds in broccoli is by 9.1% higher, in Chinese cabbage – by 10.5%. In case of Chinese cabbage, differences remained until the end of the experiment (on the 18th day from sowing seeds), in case of broccoli they were smoothed out. Comparison of two kinds of cabbage has showen that broccoli in the closed system of the synergotron forms a much higher aboveground biomass than Chinese cabbage (on the 4th day after sowing – by 37%, on the 18th day – by 75.4% in the dark version).Актуальность. При выращивании растений в искусственных условиях (закрытые агроэкосистемы) требуется четкое регулирование факторов роста растений, начиная с первых этапов онтогенеза. Одним из важных параметров является наличие или отсутствие света в период прорастания семян. Для большинства разновидностей капусты стандартным методом является проращивание в темноте, однако для свежеубранных семян (в состоянии покоя) необходимо воздействие света. По литературным данным, механизмы воздействия света на прорастание семян носят комплексный, неоднозначный характер и вопрос нуждается в детальных исследованиях.Методы. Целью работы являлось изучение прорастания семян брокколи (Brassica oleracea var. italica Plenck) и капусты китайской (Brassica rapa var. chinensis) с учетом светового фактора и одновременным анализом антиоксидантной активности как маркера изменения метаболических процессов.Результаты. Выявлено существенное повышение антиоксидантной активности микрозелени при проращивании в темноте в сравнении с проращиванием на свету (у брокколи – в 5,5 раз, у капусты китайской – в 4,8 раза). После перемещения микрозелени на свет, различия между световым и темновым вариантами практически исчезали. После прорастания на свету антиоксидантная активность микрозелени в сравнении с исходной (сухих семян) снижалась в 3-3,5 раза, в то время как в темноте – наоборот, увеличивалась в 1,5-1,6 раза. При этом конечные результаты проращивания (энергия прорастания и всхожесть семян) практически не различались по вариантам. При темновом проращивании высота микрозелени больше (за счет этиолирования и вытягивания при отсутствии света), однако в дальнейшем различия по вариантам сглаживаются. Биомасса микрозелени на свету на 4-е сутки после посева семян у брокколи – выше на 9,1%, у капусты китайской – на 10,5%. У капусты китайской различия сохранялись до завершения эксперимента (на 18-е сутки от посева семян), у брокколи – сглаживались. Сравнение двух разновидностей капусты показало, что брокколи в замкнутой системе синерготрона формирует значительно большую надземную биомассу, чем капуста китайская (на 4-е сутки после посева – на 37%, на 18-е сутки – на 75,4% в темновом варианте).