2025-02-17 シンガポール国立大学 (NUS)
＜関連情報＞
- https://news.nus.edu.sg/fundamental-proof-of-quantum-mechanics/
- https://www.cell.com/newton/fulltext/S2950-6360(25)00009-X
核スピンの一様歳差運動による量子性の証明 Certifying the quantumness of a nuclear spin qudit through its uniform precession
Arjen Vaartjes∙ Martin Nurizzo∙ Lin Htoo Zaw∙ … ∙ David N. Jamieson∙ Valerio Scarani∙ Andrea Morello
Newton Published:February 14, 2025
DOI:https://doi.org/10.1016/j.newton.2025.100017
Accessible overview
It is widely believed that the quantum mechanical precession of a spin behaves similarly to the precession of a classical gyroscope. Contrary to this conventional wisdom, the present work highlights that such similarity only holds in special circumstances, such as two-dimensional spins (qubits) or semi-classical states of larger spins. The work proposes a simple protocol that enables the quantumness of a spin system to be determined through measurements of its precession. The protocol is experimentally demonstrated on the nuclear spin of a single antimony atom, implanted in a silicon nanoelectronic device. The results show significant deviations from those expected from classical systems. Such a means to certify nonclassical states could be of interest for many applications, including quantum information processing, quantum sensing and quantum foundations.
Highlights
•The quantumness of a spin state can be certified by measuring its precession
•Exotic states of an antimony nuclear spin are certified quantum by this method
•The key requirement is measuring the positivity instead of the spin projection
•The method is resource efficient and may find widespread application
Summary
Spin precession is a textbook example of the dynamics of a quantum system that exactly mimics its classical counterpart. Here, we challenge this view by certifying the quantumness of exotic states of a nuclear spin through its uniform precession. The key to this result is measuring the positivity, instead of the expectation value, of the x-projection of the precessing spin, and using a spin >1/2 qudit that is not restricted to semi-classical spin coherent states. The experiment is performed on a single spin-7/2 123Sb nucleus, implanted in a silicon nanoelectronic device, amenable to high-fidelity preparation, control, and projective single-shot readout. Using Schrödinger cat states and other bespoke states of the nucleus, we violate the classical bound by 18 standard deviations, proving that no classical probability distribution can explain the statistic of this spin precession and highlighting our ability to prepare quantum resource states with high fidelity in a single-atomic-scale qudit.
