How do I design the microwave input line filtering to block thermal photons while passing control pulses?

Designing the microwave input line filtering to block thermal photons while passing control pulses uses a combination of attenuators and filters at each cryogenic temperature stage to progressively reduce the thermal photon population reaching the qubit, while maintaining sufficient signal level for qubit control. The challenge: room-temperature microwave equipment generates thermal noise across a wide bandwidth (approximately -174 dBm/Hz at 300K). At the qubit frequency (5 GHz): the thermal photon number at 300K is n_th approximately 1300. At the qubit chip (20 mK): n_th must be much less than 0.01 (approximately -200 dBm/Hz) to avoid thermally exciting the qubit. The required total attenuation: greater than approximately 60 dB from 300K to the mixing chamber. The filter/attenuator chain: at 300K (room temperature): the signal generator outputs the control pulse at +0 to +10 dBm. At 4K stage: install 20 dB attenuator (thermalized to 4K). This reduces the 300K thermal noise by 20 dB and replaces it with 4K thermal noise. At still stage (700 mK): install 10-20 dB attenuator. At cold plate (100 mK): install 10-20 dB attenuator. At mixing chamber (20 mK): install 10-20 dB attenuator. Additionally: install a low-pass or bandpass filter at the mixing chamber to reject out-of-band thermal noise. The filter passes only the qubit control frequencies (e.g., 4-8 GHz) and rejects everything else (especially infrared radiation that propagates as a multimode signal in the coaxial cable).