Bypassing the bandwidth theorem with PT symmetry
  The beat time {\tau}_{fpt} associated with the energy transfer between two coupled oscillators is dictated by the bandwidth theorem which sets a lower bound {\tau}_{fpt}\sim 1/{\delta}{\omega}. We show, both experimentally and theoretically, that two coupled active LRC electrical oscillators with parity-time (PT) symmetry, bypass the lower bound imposed by the bandwidth theorem, reducing the beat time to zero while retaining a real valued spectrum and fixed eigenfrequency difference {\delta}{\omega}. Our results foster new design strategies which lead to (stable) pseudo-unitary wave evolution, and may allow for ultrafast computation, telecommunication, and signal processing. 
Hamidreza Ramezani (1), J. Schindler (1), F. M. Ellis (1), Uwe   Guenther (2), Tsampikos Kottos (1) ((1) Department of Physi...
physics.class-ph cond-mat.other quant-ph