Question 1

Where should I place HERD filters in my cryostat?

Accepted Answer

The HERD application note recommends installing filters below the cryostat base plate and as close as possible to the QPU. For best performance, it recommends HERD on all lines connected to the QPU.

Question 2

How does HERD compare to other filtering approaches?

Accepted Answer

Absorptive filters can introduce significant in-band loss, while resonant structures have narrow bandwidths. HERD directs high-frequency radiation away from the main path and into an absorptive region; low-frequency radiation does not enter that region.

Question 3

Is HERD compatible with spin qubits as well as superconducting qubits?

Accepted Answer

Yes. HERD-2 is built entirely from non-magnetic materials, so it adds no stray fields to the cold stage. That makes it safe to mount close to the device for both flux-sensitive superconducting qubits and magnetically sensitive spin qubits.

Question 4

What about temperature staging requirements?

Accepted Answer

HERD filters are designed for direct mounting at millikelvin temperatures without intermediate thermal staging. The non-magnetic construction and compact SMA inline form factor simplify integration into existing cryostat wiring. No active cooling or special thermal anchoring beyond standard practices is required.

Question 5

Which connector configurations are available?

Accepted Answer

HERD-2 is available with SMA, SMP, SMPM and SMPS connectors, and HERD-1 with SMA F/F. Male/female connector options are available as custom configurations; contact us with your requirements.

Question 6

Are the published specifications measured at room temperature?

Accepted Answer

Insertion loss and attenuation figures are typical values measured at room temperature (295 K). The filters are specified for operation from 0 K to 320 K and are designed, manufactured and tested for stable operation at the millikelvin temperatures inside dilution refrigerators.

Question 7

Are the filter materials and construction reliable?

Accepted Answer

HERD filter materials are validated through thermal cycling and long-term operation in research cryostats. The construction withstands repeated cooldowns, and specifications hold across the full operating temperature range. Each unit is tested individually.

Frequently asked questions