Josephson-logic devices and circuits

Gheewala, T.

doi:10.1109/t-ed.1980.20123

Cited by 52 publications

(10 citation statements)

References 24 publications

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“…Alternatively, one could use a separate current line or a multiturn input coil. 10 However, for the former the coupling of the input flux to the SQUID will generally be a͒ Present address: Lehrstuhl für Experimentalphysik II, Universität Tübingen, 72076 Tübingen, Germany. b͒ Present address: Physikalisch-Technische Bundesanstalt Berlin, Abbestr.…”

Section: A Symmetric Squidsmentioning

confidence: 99%

“…b͒ Present address: Physikalisch-Technische Bundesanstalt Berlin, Abbestr. 10 worse than for direct coupling, while the latter requires an additional superconducting layer, complicating the fabrication particularly for high-T c materials. Furthermore, a multiturn input coil involves a higher inductance in the input circuit, which might limit the speed of the device.…”

Section: A Symmetric Squidsmentioning

confidence: 99%

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Current amplification with asymmetric direct current superconducting quantum interference devices at 77 K

Kleiner

Koelle

Ludwig

et al. 1996

Journal of Applied Physics

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Articles you may be interested inCryogenic direct current superconducting quantum interference device readout circuit Rev. Sci. Instrum. 76, 074701 (2005); 10.1063/1.1947880 Characteristics of asymmetric superconducting quantum interference devices One can use a direct current ͑dc͒ superconducting quantum interference device ͑SQUID͒ as a current amplifier by injecting a signal current I s into part of the superconducting loop and detecting the resultant change in critical current I c . The current gain max ͉dI c /dI s ͉ can be increased by making the inductances of the two arms of the SQUID asymmetric, thereby skewing the transfer function I c vs I s . Detailed simulations of the device performance include an analysis of the impact of inductance and junction asymmetry on the transfer function. At 77 K a maximum current gain of 5 should be achievable albeit for frequencies below 1 GHz. An increase in the operating speed to 2 GHz can be achieved by reducing the gain to 2. We have fabricated asymmetric YBa 2 Cu 3 O 7Ϫx dc SQUIDs on SrTiO 3 bicrystal substrates and operated them at 77 K. Using a second, readout SQUID to monitor changes in the critical current, we have achieved a low-frequency current gain up to 2.3. By coupling two SQUIDs together, we have increased the gain to 8.5.

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Section: A Symmetric Squidsmentioning

confidence: 99%

Section: A Symmetric Squidsmentioning

confidence: 99%

Current amplification with asymmetric direct current superconducting quantum interference devices at 77 K

Kleiner

Koelle

Ludwig

et al. 1996

Journal of Applied Physics

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“…As with negative resistance circuits, Josephson circuits did not provide standard values for digital signals. Circuits divided a twodimensional current space into two regions and switching meant moving the state of a circuit from one region to another [15]. Because device variability appeared as uncertainty in the locations of the boundaries between regions, just as in the case of negative resistance devices, large signals were needed to be sure of switching and the outgoing signal depended on the devices that produced it.…”

Section: Josephson Computersmentioning

confidence: 99%

Component variability as a limit in digital electronics

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2008

J Comput Electron

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Commercially successful electronic computers have been built with vacuum tubes and with transistors as active devices. Attempts to build computers with circuits based on other kinds of solid state devices have failed in spite of being the focus of large, well-funded efforts. The tunnel diode was invented shortly after the transistor and was the earliest of these. Josephson junctions and resonant tunneling devices also attracted massive investments as possible but unsuccessful alternatives to transistor based logic.What happened? Why did large development efforts devoted to these novel technologies fail? The answer is found in their inability to deal with the variability inevitably found in nominally identical parts. Transistors and vacuum tubes act as switches that form logic signals from standards that are distributed and recognizable throughout a system, signals that do not depend on the switching device that produced them. High gain is needed to emulate switches and is only obtained by using the attractive force between positive and negative charges as a gate to control current.

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“…14 shortest OR-gate delay has been 24 13 ps. The corresponding power delay time product is W 200 aJ [26].…”

Section: Single Josephson Junctionmentioning

confidence: 99%