Radio-frequency quantum photonics with photon-pressure coupled LC circuits

• Applicant: Dr. Daniel Bothner
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 490939971

The ability to detect and control physical systems with a level of precision, that is limited only by quantum mechanical uncertainties, has facilitated the development of ground-breaking sensing and detector technologies, has enabled various scientific discoveries and has initiated the age of quantum information science. For electromagnetic fields and electrical circuits, two of the most basic and important building blocks of modern technologies, this quantum regime is accessible currently from the GHz regime to the X-ray domain. For lower frequency photons in the MHz and even kHz domain, however, a frequency range highly relevant for many research fields from medicine to the search for dark matter, quantum control and quantum sensing are still prevented by thermal effects and decoherence.The objective of this proposal is to tackle this challenge and to achieve quantum-limited sensing and quantum-level control of electrical circuits in the MHz radio-frequency domain. To this end, we will use a novel, recently pioneered interaction between two superconducting circuits: photon-pressure coupling. Photon-pressure coupling is an engineered interaction between two electrical resonant circuits, that is equivalent to the interaction between light and mechanical displacement in a cavity optomechanical system. Cavity optomechanics on the other hand has already demonstrated remarkable progress towards quantum control of mechanical motion, i.e., towards radio-frequency quantum phononics. The concept behind the exciting possibilities of photon-pressure interacting circuits is that a thermal low-frequency oscillator can be detected and controlled by an additional high-frequency device, which is naturally in the quantum ground-state (for this proposal a superconducting GHz circuit in a dilution refrigerator). Within this project, we will transfer some of the most exciting schemes of opto-mechanics to electrical circuits, in particular the preparation of quantum squeezed states in an RF circuit, back-action evading measurement of RF currents and quantum entanglement between two RF circuits. As second research line, we will realize a new form of photon-pressure interaction, so-called dissipative photon-pressure, which will give additional control and sensing possibilities and in particular open the door for extremely low-frequency quantum circuits, possibly down to the kHz regime.The results of this proposal will be a big step towards radio-frequency quantum photonics, will significantly advance the young field of photon-pressure coupled circuits and have potential implications and applications for a large variety of experiments and technologies, from quantum-enhanced search for dark matter axions and quantum RADAR to radio-frequency quantum galvanometry and quantum-enhanced spin resonance detectors.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr. Reinhold Kleiner; Professor Dr. Dieter Kölle