Ultra-low-loss
IR-blocking filters
Infrared radiation breaks Cooper pairs and limits qubit coherence. HERD drains it on every line, with a flat passband.
- Insertion lossDC–8 GHz
- 0.25 dB typ.
- Attenuation70–120 GHz
- >60 dB typ.
Loss and attenuation are typical values at room temperature.
Used by groups at Yale · Princeton · KIT · MIT · UC Berkeley · Cornell · EPFL · TU Delft · PTB · Chalmers
HERD filters
Ultra-low-loss IR-blocking filters for superconducting and spin qubits.
2nd generation
HERD-2
Non-magnetic filter that removes infrared radiation from coaxial lines, with ultra-low in-band loss.
- Insertion lossDC–8 GHz
- 0.25 dB typ.
- Attenuation70–120 GHz
- >60 dB typ.
- Stopband
- 70 GHz and beyond
- Connectors
- SMA
How HERD compares
Of these four components, only HERD-2 combines ultra-low in-band loss with high suppression above 70 GHz.
Frequency (GHz)
S21 measured at room temperature, smoothed with a 1.4 GHz moving average. Above about 120 GHz the HERD-2 trace is limited by the VNA noise floor.
4 to 8 GHzSuppression,
70 to 120 GHz
More in the application note and the HERD-2 datasheet.
Published work using HERD
30+ papers from 15+ institutions worldwide using HERD in their setups.
- Yale UniversityDevoret group
Recovery dynamics of a gap-engineered transmon after a quasiparticle burst
H. Nho et al.Phys. Rev. Lett. 136, 050601 (2026)arXiv:2505.08104
HERD on each RF line inside the light-tight shield at the mixing chamber, with parity switching from stray pair-breaking photons at 0.2 to 1.2 per second.
- Princeton UniversityHouck and de Leon groups
Millisecond lifetimes and coherence times in 2D transmon qubits
M. P. Bland et al.Nature 647, 343–348 (2025)arXiv:2503.14798
HERD on the qubit drive line and the readout input line at 20 mK.
- Karlsruhe Institute of TechnologyPop group
Quantum coherent manipulation and readout of superconducting vortex states
A. Nambisan et al.Nature 653, 63–67 (2026)arXiv:2510.19769
HERD directly on the sample holder's single readout and control line at 20 mK.
- Yale UniversityDevoret group
Benchmarking the readout of a superconducting qubit for repeated measurements
S. Hazra et al.Phys. Rev. Lett. 134, 100601 (2025)arXiv:2407.10934
HERD at the strongly coupled port, inside the light-tight Cryoperm shield at the mixing chamber.
- MITOliver group
ZZ-Free Two-Transmon CZ Gate Mediated by a Fluxonium Coupler
J. An et al.arXiv:2511.02115
HERD on the readout line inside the sample can at 20 mK, directly at the device.
- TU Delft / QuTechKouwenhoven group
Majorana parity qubit in coupled minimal Kitaev chains
F. Zatelli et al.arXiv:2607.09511
HERD on the RF readout line inside the IR shield at the mixing chamber.
- 30+ papers from 15+ institutionsHERD filters are used by groups at Yale, Princeton, KIT, MIT, UC Berkeley, Cornell, EPFL, TU Delft, PTB, Chalmers, and more.All papers using HERD
Why HERD
One filter for readout, charge, and flux lines alike.
0.25dB
Insertion lossDC–8 GHz
About the same as an equal length of coaxial cable with SMA connectors. On readout lines, ultra-low loss between the QPU and the first amplifier preserves the signal-to-noise ratio.
<0.02dB
Passband ripple4–8 GHz
On charge lines, low ripple preserves pulse shapes and leaves the attenuation profile to the attenuators.
DC–23GHz
Passband3 dB cutoff, typ.
On flux lines, the DC bias passes through the filter.
>60dB
Attenuation70–120 GHz
In a stopband measured to 145 GHz. On every line, Cooper-pair-breaking radiation is drained before it reaches the QPU.
0.2–1.2/s
Parity-switching rate
Measured by the group of M. Devoret at Yale on charge-sensitive transmons, with well-thermalized HERD filters inside a light‑tight shield.
Non-magnetic
Materials
Rated from 0 K to 320 K, and suited to magnetically sensitive setups with superconducting or spin qubits.
Loss, ripple, and attenuation are typical values at room temperature.
How HERD works