The macroscopic qubit delusion

TL;DR

This paper critically examines the concept of macroscopic qubits, arguing that under realistic conditions, their interpretation as true qubits may be misleading despite experimental support, especially in semiclassical systems.

Contribution

It demonstrates how the false qubit interpretation can be consistent with existing experimental data on semiclassical systems like Bose-Einstein condensates.

Findings

False qubit interpretation can align with experimental data

Semiclassical systems may not exhibit true quantum qubit behavior

Recent experiments do not conclusively prove macroscopic qubits are genuinely quantum

Abstract

There exists a large number of experimental and theoretical results supporting the picture of "macroscopic qubits" implemented, for instance, by Rydberg atoms, Josephson junctions or Bose-Einstein condensates - the systems which should rather emerge in localized semiclassical states. In this note it is shown how, under realistic conditions, the false qubit interpretation can be consistent with the restricted set of experimental data collected for semiclassical systems. The recent experiments displaying semiclassical character of Bose-Einstein condensates and possible quantumness tests for a single system are briefly invoked also.