Recent experimental work on point-contact dc squid

Kenneth R. Carroll, Ho Jung Paik

Aashish A. Clerk

We study the backaction noise and measurement the efficiency (i.e., noise temperature) of a dc SQUID amplifier and, equivalently, a quantum point-contact detector formed in a Luttinger liquid. Using a mapping to a dissipative tight-binding model, we show that these systems are able to reach the quantum limit even in regimes where several independent transport processes contribute to the current. We suggest how this is related to the underlying integrability of these systems.

M. B. Ketchen

Ho Jung Paik, R.H. Mathews, Maria Gabriella Castellano

The well-developed technique of a toroidal point-contact rf SQUID has been extended to a dc SQUID. Two point-contacts are made on the symmetry axis of the toroid. A large Nb cavity containing a signal coil is connected to the junctions via a narrow gap. Such geometry allows good coupling of the SQUID to a high-inductance signal coil without increasing the effective SQUID inductance at the Josephson frequency. It is expected that both the shot-noise-limit performance and a high signal coupling will be achieved in this SQUID. We discuss the status of design and the result of preliminary test of the device.

Heikki Seppä, Tapani Ryhänen, Risto Juhani Ilmoniemi +1 more

Sebastian Kempf