Background

HQubit is dedicated to improving Quantum Qubit Fidelity. During our research, the influence of quantum quasiparticles and interference from cosmic radiation are significant factors. Through multiple verifications, the infrared filters developed by HQubit can significantly reduce the impact of radiant noise on Qubits (verified by the research group).

Set up

We combine DC bias and RF signals at 10mK using a bias-tee before sending them to the chip. Infrared filters are used at both the common port of the bias tee and the readout line to effectively absorb infrared radiation. Furthermore, a cryogenic u-metal shield is utilized on the sample port for shielding purposes. This combined solution can isolate infrared and magnetic radiation remarkably and is consistent with observations reported by other research groups.

Results

Based on the above findings, we believe that the shield and infrared filter are effective in blocking stray photons of around 100 GHz (or higher) from reaching the sample via open space and cables.