Non-Destructive Measurement of Macroscopic Quantum States in a Superconducting Single Electron Transistor
Abstract
The superconducting single electron transistor (SSET) is a macroscopic quantum system whose ground and excited states can be probed by measuring the supercurrent through the device. A direct measurement of the supercurrent is difficult because there is no corresponding dc voltage. Previous work has measured the current at which the SSET switches into the voltage state. However, such a measurement destroys the quantum state of the system. We discuss the design of a novel measurement system for the SSET using a SQUID to measure the transistor's supercurrent. A superconducting loop shorts the SSET drain and source together, holding the transistor in the zero dc voltage state. The supercurrent flowing in this loop depends on two parameters: The SSET gate voltage and the external magnetic flux through the loop. The SSET supercurrent is measured by a series-array of 100 dc-SQUIDs, which is coupled to the SSET loop via a microfabricated superconducting transformer. In a properly filtered environment, the dc supercurrent should attain its theoretically predicted value, without the possibility of switching into the voltage state. The goal of this work is the spectroscopic study of transitions between the ground and excited bands of this macroscopic quantum system, by the application of microwave excitations to the device inputs.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 1997
- Bibcode:
- 1997APS..MAR.R1302S