Penrose Tap

Sir Roger Penrose proposed that a particle entering a spinning black hole's ergosphere — a region where spacetime itself is dragged along by the rotation — could split in two. One piece falls in carrying negative energy (slowing the black hole slightly), while the other escapes with more energy than the original particle. A genuine loophole in conservation laws, powered by the black hole's rotational kinetic energy.

CUNY physicists built a ring of 16 electronic resonators that never physically rotates. Instead, they modulate each node in a rapid, precisely timed sequence that propagates around the ring — creating a traveling phase pattern indistinguishable from true rotation to any electromagnetic wave passing through it. Crucially, the synthetic speed can be dialed far beyond any mechanical limit.

The experiment produced 7.8 dB of net wave amplification without any energy input to the wave itself — the extra energy comes from the modulation source, just as Penrose's escaping particle draws from the black hole's spin. This validated superradiance, the wave-mechanical analog of the Penrose process, in a controlled benchtop environment for the first time.

When electromagnetic waves scatter off a rotating object, they can come back amplified — this is superradiance. It was predicted in 1972 by Zel'dovich and has been observed in rotating acoustic systems, but electromagnetic superradiance at frequencies relevant to real physics had never been demonstrated until the CUNY experiment used synthetic rotation to remove all mechanical barriers.

The synthetic-rotation amplifier principle opens paths to new non-reciprocal amplifier designs for optics and wireless communications, and provides a laboratory testbed for studying quantum vacuum amplification near rotating bodies. Because the effective rotational speed is purely a software parameter, researchers can explore regimes that would require a black hole spinning near its absolute physical limit.