Abstract: An increasing number of applications in fundamental physical and quantum research require the detection and quantitative measurement of very small power at high frequencies. Traditionally, semiconductors are employed for this purpose. A disadvantage of the transistor is the relatively high heat production of the chip that makes it difficult to cool the device to very low temperatures required to achieve a very low thermal noise. As an alternative, the use of a superconducting quantum interference device (SQUID) as a radio frequency amplifier has been suggested. A SQUID is an extremely sensitive detector of magnetic flux, and usually employed in low-frequency applications, including gravity wave detection, susceptometry, biomagnetism, nondestructive evaluation, and magnetic resonance imaging. However, the SQUID has also emerged as a suitable candidate for rf amplifiers, as due to its extremely low power dissipation and unsurpassed noise properties. Indeed, a noise temperature of close to the quantum limit has been achieved by SQUID amplifiers operating at several hundred MHz, an order of magnitude lower than that of available semiconductors. The talk will review the operational principle of the SQUID and manufacturing SQUIDs in thin-film technology, and will give a brief overview of traditional SQUID applications at low frequencies. SQUID rf amplifiers and their application in fundamental research, such as the axion detector and semiconducting quantum point contacts, are then discussed in some detail.
Speaker: Michael Mueck, ezSQUID/Justus-Liebig-University Giessen
Host: TBA
Keywords: CFP, Physics
Laura Nevins
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