The impossibility of Landauer's bound for almost every quantum state

TL;DR

This paper shows that Landauer's bound cannot be achieved for almost all initial quantum states during reset, highlighting fundamental limits on energy dissipation and decoherence in quantum information processing.

Contribution

It proves the unachievability of Landauer's bound for nearly all initial states and analytically characterizes the minimally dissipative state for qubit resets.

Findings

Landauer's bound is unachievable for almost every initial state.

Analytical expression for minimally dissipative state in qubit reset.

Verification of a theorem on initial-state dependence of entropy production.

Abstract

The thermodynamic cost of resetting an arbitrary initial state to a particular desired state is lower bounded by Landauer's bound. However, here we demonstrate that this lower bound is necessarily unachievable for nearly every initial state, for any reliable reset mechanism. Since local heating threatens rapid decoherence, this issue is of substantial importance beyond mere energy efficiency. For the case of qubit reset, we find the minimally dissipative state analytically for any reliable reset protocol, in terms of the entropy-flow vector introduced here. This allows us to verify a recent theorem about initial-state dependence of entropy production for any finite-time transformation, as it pertains to quantum state preparation.