Terahertz quantum sensing with bilayer graphene quantum dots in resonators

• Applicant: Professor Dr. Christoph Stampfer
• Subject Area: Experimental Condensed Matter Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 534269806

The emerging realm of quantum technologies promises unprecedented advances in fields such as sensing, high-performance computing, simulation, cryptography, and metrology. These technologies have been so far implemented predominantly in the microwave and optical regimes and have an untapped potential in the terahertz (THz) spectral range. Exploiting this frequency domain could have a number of benefits, including superior wireless communication security through quantum cryptography, and increase the operating temperature of solid-state qubits, thus potentially overcoming existing scalability issues. Moreover, THz radiation's ability to manipulate quantum states of molecules paves the way for new quantum computation and simulation platforms. Finally, the transmissivity through otherwise opaque materials, or robustness against Rayleigh scattering may be important assets of THz radiation for quantum sensing applications. Despite these prospects, THz quantum systems are fairly unexplored due to the relative immaturity of THz technology compared to microwave and optical counterparts. To date, there are very few achievements of quantum sensing at THz frequencies. "ThinQ" proposes a pioneering endeavor into the underexplored realm of terahertz (THz) quantum sensing. By leveraging the unique electronic properties of Bernal-stacked bilayer graphene (BLG) quantum dots (QDs) coupled to THz resonators, the project aims to develop a new technology for THz quantum sensing that goes beyond the standard quantum limit. The initiative is partitioned into two primary focus areas. The first concentrates on the development and characterization of THz photon detectors. This will utilize BLG double QDs (DQDs) coupled to a high-quality factor THz resonator to enhance light-matter interaction and to improve directivity for photon-to-electron conversion. The goal is to demonstrate THz photon detection with superior quantum efficiency and refine the approach for single THz photon detection. The second focus area embarks on quantum sensing beyond the standard quantum limit by harnessing non-classical light. By capitalizing on the strong coupling of a THz resonator with BLG DQD, we aim to generate THz squeezed light, a quantum state that surpasses classical sensor capabilities. Furthermore, the project will explore the ultra-strong coupling regime for the detection of non-classical states of THz light. In conclusion, "ThinQ" represents an audacious attempt to unlock the potential of THz quantum technology. By effectively integrating BLG QDs and THz resonators, we will develop THz detectors with unmatched sensitivity and novel building blocks for quantum sensing with squeezed light. This will open the door to novel encryption and computing schemes and contribute significantly to the advancement of quantum technology in the THz regime.

• DFG Programme: Research Grants
• International Connection: France, Sweden
• Cooperation Partners: Dr. Juliette Mangeney; Professorin Dr. Janine Splettstößer