Physics Seminar by Prasanna Venkatesh B

Time: 1400 HRS

Venue: A01-101

Title: How to charge quantum batteries quickly and discharge them fully?

Abstract: A useful quantum battery (QB) must charge fast and store energy that can be extracted as work, quantified by the ergotropy. We will first show that controlled pure dephasing of a driven charger speeds up charging: an optimal rate balances coherent oscillations at weak dephasing against Zeno freezing at strong dephasing. For N qubits charged collectively by such a dephased charger, the steady-state ergotropy-to-energy ratio approaches unity as 1−\Theta(1/N). This “asymptotic freedom” arises from an emergent near-degeneracy of the collective ground state, even though the battery remains mixed. Finally, we will see that the 1/N law is generic: it holds, with rigorous finite-N bounds, for any charged state of polynomially bounded rank. Asymptotically pure states converge faster, up to exponentially in N.