400 MHz Bandwidth Josephson Mixers Amplify Quantum Signals with 10 dB Reflection

Researchers have achieved a 400 MHz bandwidth in Josephson mixers, a substantial leap overcoming a key limitation that previously restricted the processing of frequency-multiplexed signals essential for scaling up quantum processors. These redesigned mixers, based on a Josephson ring modulator and incorporating coupled-mode networks, not only broaden signal handling capacity but also exhibit power reflections above 10 dB, indicating strong signal preservation during amplification, critical for maintaining the integrity of quantum information. The team demonstrated a saturation power of about -110 dBm at 15 dB, representing a significant increase in the signal strength these mixers can manage before…