Multi-phonon Fock state heralding with single-photon detection

TL;DR

This paper demonstrates how single-photon detection in optomechanical systems with forward Brillouin scattering can herald the creation of complex multi-phonon Fock states, advancing quantum state engineering in mechanical oscillators.

Contribution

It introduces a method to generate and herald multi-phonon Fock states using single-photon detection in systems with forward Brillouin scattering, including quantum tomography techniques.

Findings

Single-photon detection can herald multi-phonon Fock states.

Complex entangled states evolve from single photons and weak laser pulses.

Heralded phonon states can be generated despite optical losses.

Abstract

Recognized as a potential resource for quantum technologies and a possible testbed for fundamental physics, the control and preparation of nonclassical states of mechanical oscillators has been explored extensively. Within optomechanics, quantum state synthesis can be realized by entangling photonic and phononic degrees of freedom followed by optical detection. Single-photon detection enables one of the most powerful forms of such heralded quantum state preparation, permitting the creation of single phonon states when applied to conventional cavity optomechanical systems. As the complexity of optomechanical systems increases, single-photon detection may provide heralded access to a larger class of exotic quantum states. Here, we examine the quantum dynamics of optomechanical systems that permit forward Brillouin scattering, where a single phonon mode mediates transitions between a collection of equally spaced optical resonances. Solving both the Schrodinger equation and the Lindblad master equation for this system, we find that initial states comprised of single photons or weak laser pulses evolve into complex quantum states where the frequency of single photon states and the phonon occupation number are entangled. Physically, these interactions permit a single photon to scatter to lower frequencies, where phonon excitation occurs for each scattering event. Combining this result with frequency filtering, we show how single-photon detection can herald selected multi-phonon Fock states, even in the presence of optical losses. We also present an approach for quantum tomography of the heralded phonon states.