Low-noise and wide-bandwidth current readout at low temperatures using a superconducting-quantum-interference-device amplifier

摘要

We report on the development of a current amplifier for measuring small currents from mesoscopic electronic devices at low temperatures down to the milli- Kelvin range. In our setup, a superconducting quantum interference device ( SQUID) located at the mixing chamber stage of the dilution refrigerator is used as the first- stage current amplifier, thereby improving the noise floor down to 8 * 10(-27)A(/)(2)HZ , which is one order of magnitude as low as those obtained by the conventional methods that utilize a semiconductor-based cryogenic current amplifier. We show the configuration of this setup and demonstrate the amplification of the current generated by a quantum point contact. This can open a new way to examine solid-state phenomena that are elusive owing to their small current. c 2017 The Japan Society of Applied Physics