Quantum Chaos

How does the macroscopic world that we experience in our everyday life emerge from the underlying microscopic world invisible to the naked eye? This question, as old as science itself, became particularly relevant over the past 100 years in understanding how classical mechanics, governing the macroscopic world, derives from quantum mechanics, governing the underlying microscopic world . Although tremendous progress has been made, still many puzzling questions remain [Leggett2002].

 

One of the least experimentally-researched aspects of the quantum/classical crossover is the emergence of chaos. Classical nonlinear systems behaving chaotically show an extreme sensitivity to perturbations, rendering the long term behavior unpredictable although the system is fully deterministic. Due to their discrete nature, quantum-mechanical systems lack such an extreme sensitivity, and instead behave quasi-periodic. In attempting to reconcile this seemingly different behavior, many theoretical predictions have been made, impacting topics in quantum mechanics as varied as the origin of decoherence [Zurek2003], the nature of a measurement [Schlosshauer2004], the origin of thermodynamics [Srednicki1995], and fault-tolerant quantum computing [Silvestrov2001]. However, very little experiments investigating these predictions have been conducted [Hensinger2001, Steck2001, Chaudhurry2009, Manai2015, Neill2016], and none on a single quantum-mechanical degree of freedom observed in real time.

In this project, we will use the high 7/2 nuclear spin of a single antimony donor in silicon to implement a quantum-mechanical equivalent of a classically chaotic system, the driven top [Mourik2017]. To realize this, we use the existing infrastructure developed for the phosphorous qubit, replacing the donor by antimony. Our goals are to achieve full quantum-state control and high-fidelity readout of the 7/2 nuclear spin, allowing us to prepare the nuclear spin in the classically-chaotic regime, and observe  its dynamics in a time-resolved manner. For the first time, we will be able to control a single quantum object whose classical counterpart would behave chaotic, and observe it in real time. When successful, this opens up a broad scala of research possibilities to shed light upon the quantum/classical crossover in dynamics.

Vincent Mourik, Serwan Asaad, Hannes Firgau, Jarryd J. Pla, Catherine Holmes, Gerard J. Milburn, Jeffrey C. McCallum, Andrea Morello, An experimentally realizable single-atom chaotic driven top in silicon, https://arxiv.org/abs/1703.04852, 2017

Serwan Asaad, Mark Johnson, Vincent Mourik, Hannes Firgau, Andrea Morello

Jarryd Pla, UNSW, experiment

Jeffrey McCallum, University of Melbourne, donor implantation

Gerard Milburn, University of Queensland, theory

Klaus Mølmer, Aarhus University, theory