Breaking Landauer's bound in a spin-encoded quantum computer

Abstract

AbstractIt is commonly recognized that Landauer's bound holds in (irreversible) quantum measurement. In this study, we overturned this common sense by extracting a single spin from a spin–spin magnetic interaction experiment to demonstrate that Landauer’s bound can be broken quantitatively by a factor of $$10^{4} \sim 10^{10}$$ 10 4 ∼ 10 10 via quantum spin tunneling. It is the quantum limit ($$\hbar /2 \approx 10^{ - 34} \;{\text{J}} \cdot {\text{s}}$$ ħ / 2 ≈ 10 - 34 J · s ), rather than Landauer’s bound, that governs the performance of a spin qubit. An optically-manipulated spin-encoded quantum computer is designed, in which energy bound well below $$k_{B} T$$ k B T to erase a spin qubit at the expense of a long spin relaxation time is theoretically sensible and experimentally verified. This work may represent the last piece of the puzzle in quantum Landauer erasure in terms of a single spin being the smallest and the closest to the quantum limit.