RSFQ Technology: Physics and Devices

Bunyk, P.; Likharev, K. K.; Zinoviev, Dmitry

doi:10.1142/s012915640100085x

Cited by 153 publications

(68 citation statements)

References 68 publications

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“…A perceived simplicity and alleged low cost of the fabrication process were historically cited as one of the main advantages of SFQ electronics [77], [79]. At the time of RSFQ introduction in the US in 1991, the only commercial fabrication process for SCE had only three superconducting niobium layers for interconnecting Josephson junctions, a minimum feature size of 3.5 μm, used Nb/AlO x /Nb Josephson junctions, and 3-inch wafers [19].…”

Section: A Sfq Electronics Fabrication Processesmentioning

confidence: 99%

See 1 more Smart Citation

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Tolpygo¹

2016

Low Temperature Physics

177

115

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Abstract-Superconductor digital electronics using Josephson junctions as ultrafast switches and magnetic-flux encoding of information was proposed over 30 years ago as a sub-terahertz clock frequency alternative to semiconductor electronics based on complementary metal-oxide-semiconductor (CMOS) transistors. Recently, interest in developing superconductor electronics has been renewed due to a search for energy saving solutions in applications related to high-performance computing. The current state of superconductor electronics and fabrication processes are reviewed in order to evaluate whether this electronics is scalable to a very large scale integration (VLSI) required to achieve computation complexities comparable to CMOS processors. A fully planarized process at MIT Lincoln Laboratory, perhaps the most advanced process developed so far for superconductor electronics, is used as an example. The process has nine superconducting layers: eight Nb wiring layers with the minimum feature size of 350 nm, and a thin superconducting layer for making compact high-kineticinductance bias inductors. All circuit layers are fully planarized using chemical mechanical planarization (CMP) of SiO 2 interlayer dielectric. The physical limitations imposed on the circuit density by Josephson junctions, circuit inductors, shunt and bias resistors, etc., are discussed. Energy dissipation in superconducting circuits is also reviewed in order to estimate whether this technology, which requires cryogenic refrigeration, can be energy efficient. Fabrication process development required for increasing the density of superconductor digital circuits by a factor of ten and achieving densities above 10 7 Josephson junctions per cm 2 is described.

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Section: A Sfq Electronics Fabrication Processesmentioning

confidence: 99%

“…Inspection of all RSFQ, ERSFQ, etc. cells in [77]- [81], [91] shows that <I c > ≈ 175 μA. It is a result of selecting I c ≈ 100 μA as the minimum value used in the cells, based on the maximum acceptable bit error rate.…”

Section: A Josephson Junctionsmentioning

confidence: 99%

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Tolpygo¹

2016

Low Temperature Physics

177

115

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“…The escape junctions J1 and J3 shield the SFQ pulse sources from the back reaction in the case of a double set or reset pulse. The pulse stretcher is based on the same concept but now a dc-squid containing junctions J5 and J6 is coupled to the flip-flop [7], [8]. When a signal is applied to the set input, the flip-flop switches to state 1 and the junction J6 is providing a finite dc voltage at the output.…”

Section: A Description Of the Pulse Stretcher Behaviormentioning

confidence: 99%

HTS Pulse-Stretcher and Second Order Modulator: Design and First Results

Roussy

Karthikeyan

Oomen

et al. 2005

IEEE Trans. Appl. Supercond.

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Abstract-One of the remaining challenges in the application of superconducting electronics is the interfacing between superconducting and semiconducting environments. The voltage and speed mismatch between RSFQ pulses and semiconducting read-out electronics makes it necessary to amplify as well as stretch the RSFQ pulses. Moreover, circuits based on HTS (High Temperature Superconductor) technology are very attractive since they can operate under considerably relaxed cooling effort, which is one of the main problems with LTS (Low Temperature Superconductor) circuits.Within the European project SuperADC, a HTS second order sigma delta modulator and a pulse stretcher, used as an interface between the modulator and the first semi-conducting amplifier stage, have been designed at Twente University and will be presented here.Index Terms-HTS superconductors, Josephson junctions, rapid single flux quantum, superconducting/semiconducting interface circuits.

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“…Josephson junctions [1][2][3] that join two superconductors became a class of the most realistic candidates for implementing modern technologies such as qubits, [4,5] superconducting quantum interference devices (SQUIDs), [6,7] and the rapid single flux quantum (RSFQ) logic circuits. [8,9] Their mechanism is based on the Josephson effect that was developed from the quantum theory, while it cannot be explained by classical mechanics. The Cooper pairs of electrons in the superconductor that are formed below a critical temperature exhibit a collective motion.…”

Section: Introductionmentioning

confidence: 99%

“…They exhibit the ability of an extremely high-speed switching with a typical operation frequency ranging several-hundred-GHz, whereas they consume very low power. [9] For implementing Josephson junctions in the abovementioned technologies, we should consider diverse problems such as electromagnetic isolations, temperature effects, dissipations, entropies, and decoherences in the junctions. To settle these problems, the characterization of quantum features associated with the junctions, based on rigorous quantum mechanical description of the system, is important.…”

Section: Introductionmentioning

confidence: 99%

Dynamical Properties of Nanostructured Josephson‐Junction Based on the Schwinger Quantum Action Analysis

Choi

2019

Advcd Theory and Sims

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Using the Schwinger action principle, Josephson-junction dynamics for nanodevices have been investigated with emphasis on characterizing their quantum features. Starting from the time-ordered Hamiltonian for the phase of the current which flows across the junction, the propagator, the wave functions, and the joint entropy, which are crucial for quantum analyses of the nano systems, are derived. It is shown that while the propagator and the wave functions vary depending on external driving forces, the joint entropy is not affected from such forces. Interestingly, the probability densities oscillate over time on account of the influence of the time-varying supercurrent in the junction. It is confirmed that if external perturbations on the junction-current are more complicated, the time behaviors of the probability densities become conspicuously irregular. The properties of the joint entropy are also analyzed in detail. Due to damping of the system, the phase( ) component of the joint entropy decreases linearly over time, whereas the conjugate momentum(q) component exhibits linear increase; however, the corresponding joint entropy consequently does not vary. It is demonstrated that the joint entropy obeys the quantum minimum principle, and that there is a close relationship between the joint entropy and the uncertainty relation.

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RSFQ Technology: Physics and Devices

Cited by 153 publications

References 68 publications

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

Superconductor digital electronics: Scalability and energy efficiency issues (Review Article)

HTS Pulse-Stretcher and Second Order Modulator: Design and First Results

Dynamical Properties of Nanostructured Josephson‐Junction Based on the Schwinger Quantum Action Analysis

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