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Superconducting quantum interference devices (SQUIDs) are made by a superconducting loop interrupted by one or more Josephson junctions. They are described in terms of a macroscopic variable, the magnetic flux, which shows quantum effects such as tunnelling through a potential barrier. Besides making up the source of a quantum state, SQUIDs also provide the instruments necessary for its probing: as a fact, SQUID based magnetometers have a sensitivity approaching the quantum limit. In this paper I will review the working principle of these devices and illustrate the system of SQUIDs realized in my group to test the quantum behavior at a macroscopic level.

Microelectrodes consisting of a vertical structure made by the superposition of niobium, titanium and gold layers have been fabricated using electron beam lithography and thin film technique. The niobium layer improves the mechanical strength and ensures a good resistance of the structure to the galvanic corrosion which is a very important characteristic when dealing with biological particles. The proximity corrections have been applied in order to obtain the PMMA resist with a suitable profile for the lift-off of the TiAulayers. This corrections allowed us to setup the process to obtain electrode gaps down to 0.2μm.

Microelectrodes consisting of a vertical structure made by the superposition of niobium, titanium and gold layers have been fabricated using electron beam lithography and thin film technique. The niobium layer improves the mechanical strength and ensures a good resistance of the structure to the galvanic corrosion which is a very important characteristic when dealing with biological particles. The proximity corrections have been applied in order to obtain the PMMA resist with a suitable profile for the lift-off of the TiAu layers. This corrections allowed us to setup the process to obtain electrode gaps down to 0.2μm.