A Twisted Pair Cryogenic Filter
  In low temperature transport measurements, there is frequently a need to protect a device at cryogenic temperatures from thermal noise originating in warmer parts of the experiment. There are also a wide range of experiments, such as high precision transport measurements on low impedance devices, in which a twisted-pair wiring configuration is useful to eliminate magnetic pickup. Furthermore, with the rapid growth in complexity of cryogenic experiments, as in the field of quantum computing, there is a need for more filtered lines into a cryostat than are often available using the bulky low temperature filters in use today. We describe a low cost filter that provides the needed RF attenuation while allowing for tens of wires in a twisted pair configuration with an RF-tight connection to the sample holder. Our filter consists of manganin twisted pairs wrapped in copper tape with a light-tight connection to the shield of the sample holder. We demonstrate agreement of our filter with a theoretical model up to the noise floor of our measurement apparatus (90 dB). We describe operation of our filter in noise thermometry experiments down to 10 mK. 
Lafe Spietz, John Teufel, and R. J. Schoelkopf