Measurement and control of single-photon microwave radiation on a chip

Real-time single microwave photon detection is an emerging capability in quantum mechanics applications, such as quantum computing, quantum measurements and in ultrasensitive spectroscopy in cryogenic environments. However, unlike optical quantum detection, there are no detectors that can reliably resolve single microwave photons. A fundamental reason for this is the much lower energy of the microwave photon compared to that of an optical photon. This means that detecting microwave photons relies on extremely sensitive detectors, operating in highly shielded environments at ultra-low temperatures. New single microwave photon technologies are required to improve the performance and sensitivity of quantum microwave devices and so reduce background effects in cryogenic environments to promote the development of on-chip microwave components.

The project Controlling single-photon microwave radiation on a chip (MICROPHOTON) developed single photon microwave sources and detectors and investigated the sources of interference in cryogenic measurement systems.

The project:

• Developed single-microwave-photon detectors for use between 8 GHz and 80 GHz based on superconductor and semiconductor nanotechnologies.
• Developed and characterised two types of single microwave photon sources which are suitable for integration with superconducting-normal metal-superconducting thermal detectors. • Determined for the first time, the frequency and power function responses of a cryo-electronic quantum nano-detector using on-chip-generated microwaves.
• Constructed a measurement chamber for studying the effects of microwave background radiation on cryo-electronic devices.
• Used external magnetic fields to prevent background microwave photon interference effectively via on-chip leads during microwave measurements.

In this project, for the first time experiments using on-chip microwave technologies for generating, transmitting and detecting microwaves were performed. These advances support the development of signal amplifiers for wireless communications and radiation measurements. The project’s microwave photon detectors and sources have the potential to assist in the characterisation of novel microwave applications including the realisation of practical quantum computing based on solid-state qubits.

EMPIR project 17FUN10 ParaWave builds on this work.