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The QFilter

The QFilter is a compact multi-stage low-pass filter which applies patented technology* to reject noise and to ensure mil­likelvin electron temperature in up to 48 signal lines going to your quantum electronics devices and other sensitive cryogenic circuits. It is the result of several years of development at Harvard University and University of Copenhagen on achieving the lowest possible noise and electron temperature in quantum circuits. The standard QFilter contains two filter banks, one with RC circuits and one with LC circuits, but other combinations can also be supplied.

QFilter with 25 pin micro-D connectors and high thermal conductivity body

The QFilter will both thermalize the electrical leads and electrons to the sample, and filter out electrical noise from about 50 kHz to tens of GHz.

Summary

  • 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 is achieved by connecting the RC and RF lines in series using an optional jumper cable.
  • QFilters can be stacked or mated in-series to save space or cables respectively.
  • Compact size of 30 mm x 47 mm x 70 mm.

Radio frequency low-pass filter bank (RF)

  • Three reflective 7-pole Pi filter stages, individually shielded
  • Attenuates above 80 MHz
  • Total resistance (room temp.): 2.5±0.2 Ω
  • Isolation to ground and other channels > 2 GΩ (room temp.)
The QFilter with the optional 6-inch jumper cable connecting the 24-channel RC and RF filter banks in series.

The QFilter with the optional 6-inch jumper cable connecting the 24-channel RC and RF filter banks in series.

Low frequency low-pass filter bank (RC)

  • One reflective 7-pole Pi and two dissipative RC filter stages, individually shielded
  • Attenuates from 50 kHz or lower
  • Total resistance (room temp.): 1700±10 Ω
  • Isolation to ground and other channels > 2 GΩ (room temp.)

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