Toward engineered quantum many-body phonon systems

TL;DR

This paper explores the feasibility of creating quantum many-body phonon systems using silicon-based coupled phonon cavities with impurity qubits, demonstrating potential for observing phase transitions like Mott insulator and superfluid states.

Contribution

It proposes experimentally feasible silicon-based architectures for quantum many-body phonon states, analyzing both equilibrium and non-equilibrium conditions, and highlights the role of temperature and driving fields.

Findings

Quantum many-body phonon states are achievable in silicon nanomechanical systems.

Temperature and driving fields critically influence the realization of superfluid and insulator states.

Detection methods for these quantum states are proposed.

Abstract

Arrays of coupled phonon cavities each including an impurity qubit in silicon are considered. We study experimentally feasible architectures that can exhibit quantum many-body phase transitions of phonons, e.g. Mott insulator and superfluid states, due to a strong phonon-phonon interaction (which is mediated by the impurity qubit-cavity phonon coupling). We investigate closed equilibrium systems as well as driven dissipative non-equilibrium systems at zero and non-zero temperatures. Our results indicate that quantum many-body phonon systems are achievable both in on-chip nanomechanical systems in silicon and distributed Bragg reflector phonon cavity heterostructures in silicon-germanium. Temperature and driving field are shown to play a critical role in achieving these phonon superfluid and insulator states, results that are also applicable to polariton systems. Experimental procedures to detect these states are also given. Cavity-phoniton systems enable strong phonon-phonon interactions as well as offering long wavelengths for forming extended quantum states; they may have some advantage in forming truly quantum many-body mechanical states as compared to other optomechanical systems.