Events

  Certifying the quantumness of a single nuclear spin qudit through its uniform precession

Martin Nurizzo (UNSW Sydney)

Date/Time: Tuesday, 10th September 2024 at 2:00 pm

Place: Room Rémy Lemaire K223, Institut Néel

Abstract: Although qubits are prime examples of quantum systems, single qubits can only host semi-classical spin coherent states. Qudits, on the other side, can exhibit non-classical states, which cannot be described by a classical probability distribution. Here we detect quantumness in the time evolution of a uniformly precessing 8-dimensional nuclear qudit. In this experiment quantumness is certified by asking how often the x-coordinate of a uniformly precessing state is positive 1. A violation of a classical bound in this protocol indicates the absence of a classical probability distribution that can explain the observed data, thus confirming quantumness 2. We present our experimental demonstration of this protocol focusing on a family of non-classical states in a spin-7/2 antimony nucleus, implemented within a silicon nano-electronic device 3. Our results reveal a significant violation of the classical protocol bound, surpassing it by 19 standard deviations for the spin-cat state. These findings underscore our ability to prepare arbitrary nonclassical resource states with high fidelity in a single atomic-scale qudit, with potential applications in quantum information processing, sensing and quantum error correction.
Ref.: 1 Tsirelson, B. How often is the coordinate of a harmonic oscillator positive? https://doi.org/10.48550/arXiv.quant-ph/0611147 (2006).
2 Zaw, L. H., Aw, C. C., Lasmar, Z. & Scarani, V. Detecting quantumness in uniform precessions. Phys. Rev. A 106, 032222 (2022).
3 Yu, X. et al. Creation and manipulation of Schrodinger cat states of a nuclear spin qudit in silicon. Preprint at https://doi.org/10.48550/arXiv.2405.15494 (2024).