Angular momentum time-crystal for synthetic Penrose superradiance

The revival of interest in time-varying media has propelled research into emerging landscapes of wave-matter interactions, revitalizing conventional notions in stationary paradigms with new facets. A remarkable scenario unfolds in the time-like crystalline regime of azimuthal spatiotemporally modulated systems, where non-Hermitian momentum gaps and increased angular velocity harbor the potential for realizing Zel’dovich’s 1970s description of Penrose’s 1960s visionary proposal concerning energy extraction from a rotating black hole. Zel’dovich’s interpretation identifies a mechanism capable of amplifying quantum fluctuations and classical waves when interacting with a spinning dissipative apparatus at negative rotational Doppler-shifted frequencies. Leveraging a ring network of modulated microwave resonators, we present unequivocal experimental evidence of electromagnetic Zel’dovich amplification, aligning with expectations for operation within the angular momentum gap of time-like crystals. Our findings foster wave dynamics studies in rotating frameworks and open new frontiers in the pursuit of classical and quantum energy harvesting.