Microwave quantum diode

Area of Science:

• Quantum Computing
• Microwave Engineering
• Superconducting Devices

Background:

• Quantum circuits are sensitive to noise and amplifier backaction, hindering scalability.
• Current non-reciprocal devices (circulators, isolators) are bulky and limit cryogenic integration.
• Scalable quantum applications require compact solutions for noise mitigation.

Purpose of the Study:

• To introduce a compact microwave diode architecture for quantum circuits.
• To demonstrate the non-reciprocal transmission properties using a superconducting flux qubit.
• To provide a scalable alternative to traditional non-reciprocal devices.

Main Methods:

• Designed a microwave diode architecture exploiting the non-linearity of a superconducting flux qubit.
• Experimentally operated the device at cryogenic temperatures near the qubit degeneracy point.
• Measured transmission power in opposite directions across various frequency ranges.

Main Results:

• Demonstrated significant power transmission differences in opposite directions.
• Achieved a transmission rectification ratio exceeding 90% over a 50 MHz bandwidth (6.81–6.86 GHz).
• Reported over 60% rectification across a 250 MHz bandwidth (6.67–6.91 GHz) at -99 dBm input power.

Conclusions:

• The proposed compact microwave diode architecture is effective for non-reciprocal signal transmission.
• This scalable design offers potential for improved quantum information processing and microwave readout.
• The architecture opens opportunities in quantum information, microwave readout, and optomechanics.