Quantum confusion, a fundamental concept in the quantum theory of information, has long been seen as a significant indicator of a “quantum” system. However, the relationship between confusion and the computational power of quantum computers has not been clearly understood. In a recent study published on the preprint server arXiv, a team of physicists from Germany, Italy, and the USA delved into this intricate relationship, highlighting the importance of a property known as “magic” in the theory of confusion. The findings of this study have broad implications for various fields including quantum error correction, many-body physics, and quantum chaos.
Traditionally, it has been believed that the stronger the level of confusion in a quantum computer, the greater its computational capabilities. However, this perspective is being challenged as some highly confusing states can be effectively simulated on classical computers without exhibiting the computational power associated with other quantum states. These states are typically created using cliquon chains that are amenable to classical simulation.
To address this discrepancy, the researchers introduced the concept of “magic”, which quantifies the amount of non-Clifford resources required for preparing a quantum state and serves as a more nuanced indicator of the computational power of the state.
In this new study, graduate student Andi Gu from Harvard University, along with postdocs Salvatore F.E. Oliviero from Scuola Normale Superiore and CNR in Pisa, and Lorenzo Leon from the Center for Complex Quantum Systems in Berlin, explored the connection between confusion and magic through operations such as confusion assessment, distillation, and breeding.
The researchers focused on evaluating confusion quantitatively in a quantum system through the process of disturbance distillation. This involves using local operations and classical communication to maximize the number of Bell pairs that can be obtained from a quantum state. Conversely, breeding confusion involves the opposite task of converting copies of Bell states into less confusing states with high precision.