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Double Moat Structure for Superconductive Circuits

IP.com Disclosure Number: IPCOM000050008D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

Bermon, S: AUTHOR [+2]

Abstract

In superconductive circuits, magnetic flux sometimes becomes trapped in superconducting groundplanes. This trapped flux can couple to overlying tunnel devices and interfere with their switching characteristics. In order to prevent flux from being trapped in the vicinity of the devices, "moat" structures have been proposed wherein slits are formed in the groundplane around the area of the devices. These slits form a "moat" around the devices which are preferential sites for trapping magnetic flux. Therefore, flux cannot enter the area of the superconducting groundplane located beneath the superconductive devices. An improvement to these moat-guarded devices is described in which a double moat structure is used.

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Double Moat Structure for Superconductive Circuits

In superconductive circuits, magnetic flux sometimes becomes trapped in superconducting groundplanes. This trapped flux can couple to overlying tunnel devices and interfere with their switching characteristics. In order to prevent flux from being trapped in the vicinity of the devices, "moat" structures have been proposed wherein slits are formed in the groundplane around the area of the devices. These slits form a "moat" around the devices which are preferential sites for trapping magnetic flux. Therefore, flux cannot enter the area of the superconducting groundplane located beneath the superconductive devices. An improvement to these moat-guarded devices is described in which a double moat structure is used.

Fig. 1 shows a double-moat structure comprising an inner moat 10 and an outer moat 12. These moats are slits in the superconducting groundplane 14. A "holey" device 16 is located in the regions surrounded by the moats, the holey device being, for instance, a Josephson interferometer. This type of device utilizes holes 18 in the groundplane 14. When flux becomes trapped in a moat, it may be energetically favorable for the flux to complete a closed-loop flux path through the holes 18. Superconducting bridges 20 are narrow regions in the groundplane between the slits. The use of a double moat structure reduces this possibility by providing a more energetically favorable path for the return flux.

Moat 12 is located outside moat 10, where the separation could be as small as the minimu...