Many-Particle Quantum Engineering with Photon-Mediated Interactions

Stanford University, Stanford CA

Investigators

Abstract

A remarkable feature of quantum physics is the non-locality of information. Quantum information can be encoded not only in individual bits or atoms, but also in the correlations amongst many atoms. Such correlations -- or "entanglement" -- may one day offer profound benefits for computation and precision sensing technologies. While the potential benefits of entanglement multiply with increasing particle number, so do the challenges of manipulating and preserving it. One key difficulty is that the naturally occurring interactions among atoms are local, i.e., an atom ordinarily interacts only with other atoms that are very near it. In this project, we will engineer a new type of interaction that is non-local and can thus entangle many spatially separated atoms. We will employ laser light as a messenger for conveying information between these atoms to generate entanglement. A crucial challenge is to convey this information discreetly, without letting it leak to the surrounding environment; otherwise, the delicate quantum mechanical system would be perturbed by the mere act of observation. Addressing this challenge will require a customized experimental apparatus, which graduate and undergraduate students will construct and operate, thereby acquiring valuable technical and analytical problem-solving skills. The educational impact will be extended to students from a local two-year college through summer internships designed to broaden participation in the science and engineering workforce. This project focuses on engineering light-mediated spin-spin interactions among laser-cooled atoms. The primary motivation is to enable the study of novel many-particle entangled states emerging from beyond-mean-field collective spin dynamics. By strongly coupling many atoms to a single mode of light in an optical resonator, we will generate interactions that are highly coherent, controllable, and non-local. By furthermore combining non-local interactions with local addressing, we will harness a single quantum bit non-linearity to manipulate the many-particle collective spin. The ease of tuning and quenching light-mediated interactions, as well as varying the strength and form of dissipation, will enable investigations of the emergence of entanglement in a quantum phase transition or in quantum chaotic dynamics. Sensitive, resonator-aided measurements will enable detailed quantum-state characterization, including tomographic reconstruction into a phase-space representation allowing for visual comparison of quantum dynamics with corresponding classical trajectories.