QFilter is a compact multi-stage low-pass filter that rejects noise and ensures mil­likelvin electron temperature in up to 48 signal lines to quantum electronics devices and other sensitive cryogenic and low-temperature electronic circuits. The result of years of development at Harvard University and the University of Copenhagen, the standard QFilter contains two low-pass filter banks, one with RC circuits and one with RF (LC) circuits, and other combinations can also be supplied.

Radio Frequency Low-Pass Filter Bank (RF)

  • Three reflective 7-pole Pi filter stages, individually shielded
  • Attenuates above 225 MHz (80 MHz in previous generations)
  • Total resistance (room temp.): 2.0±0.5 Ω
  • Isolation to ground and other channels > 2 GΩ (room temp.)

Low-Frequency Low Pass Filter (RC)

  • One reflective 7-pole Pi and two dissipative RC filter stages, individually shielded
  • Attenuates from 65 kHz or lower
  • Total resistance (room temp.): 1700±10 Ω
  • Isolation to the ground and other channels > 2 GΩ (room temp.)

Key features

  • One audio frequency (RC) and one radio frequency (RF) filter board with 24 low-pass channels each
  • Designed for easy mounting on the mixing chamber plate of common dilution refrigerators
  • Sturdy design makes it possible to stack multiple filters for higher channel counts
  • Signal lines are thermally anchored to non-magnetic gold-plated copper brackets
  • Compatible with low temperatures and high magnetic fields
  • Non-magnetic shielded 25-pin microD connectors, female input, male output
  • Pinout compatible with Cinch connectors used in most dilution refrigerators
  • Optimal performance achieved by connecting RC and RF lines in series using optional jumper cable
  • QFilters can be stacked or mated in-series to save space or cables respectively
  • Compact size – 30 mm x 47 mm x 70 mm

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