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Laser Beam Control of Josephson Gate

IP.com Disclosure Number: IPCOM000079423D
Original Publication Date: 1973-Jul-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Jutzi, WW: AUTHOR [+2]

Abstract

Within their cooled environment Josephson junction gates can be controlled from outside by the application of short laser pulses to the junction area.

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Laser Beam Control of Josephson Gate

Within their cooled environment Josephson junction gates can be controlled from outside by the application of short laser pulses to the junction area.

Thermal switching of the gate from the Josephson supercurrent state to the finite voltage state is used, e.g., as signal input to a superconducting computer. For optical access, fiber-light pipes or integrated optic techniques can be applied if the junctions are not directly accessible from outside the dewar.

Permanent flux generation in a gate can be affected if at least one electrode dimension is larger than the Josephson penetration depth. This generation within the gate is achieved by laser pulse heating, in coincidence with a suitable gate current. The trapped flux is about proportional to the applied gate current. A trapped flux has the same effect like an external magnetic field. Thus the Josephson junction gate characteristic is changed.

By proper choice of the parameters during flux trapping the Josephson current can be reduced to zero. The range of nearly zero Josephson current can be enlarged by designing the effective Josephson current density distribution inside the junction, for instance by electrode shaping.

In this way, the junction operates as a settable switch where each state can be sensed nondestructively. In one state there is zero resistance, and in the other state a finite resistance corresponding to the tunnel characteristic. Restoring through flux expell...