Bell correlations between light and vibration at ambient conditions

Abstract

Time-resolved Raman spectroscopy techniques offer various ways to study the dynamics of molecular vibrations in liquids or gases and optical phonons in crystals. While these techniques give access to the coherence time of the vibrational modes, they are not able to reveal the fragile quantum correlations that are spontaneously created between light and vibration during the Raman interaction. Here, we present a scheme leveraging universal properties of spontaneous Raman scattering to demonstrate Bell correlations between light and a collective molecular vibration. We measure the decay of these hybrid photon-phonon Bell correlations with sub-picosecond time resolution and find that they survive over several hundred oscillations at ambient conditions. Our method offers a universal approach to generate entanglement between light and molecular vibrations. Moreover, our results pave the way for the study of quantum correlations in more complex solid-state and molecular systems in their natural state.

Measurement-induced collective vibrational quantum coherence under spontaneous Raman scattering in a liquid

“…We estimate that about N ~ 10 10 randomly moving molecules occupy the focal volume. If we consider them individually, the Raman interaction can be modeled as a tensor product of N two-mode squeezing unitary operators acting on the vacuum state of the Stokes photon ( S ) and the vibration ( v ) 20 , 52 . Assuming the same Raman cross-section for all the molecules and uniform field intensity within the focal volume, and ignoring corrections from time-ordering of operators 55 , 56 as valid in the low-gain regime, the state of the system after a short interaction is where p ≃ 10 −2 in our experimental conditions (low gain, spontaneous regime).…”

“…Following a pioneering work by I. Walmsley and coworkers in 2011 11 , more recent experiments have used time-correlated single photon counting to evidence non-classical intensity correlations between light fields interacting with the same phonon mode via Raman scattering, with potential applications in ultrafast quantum information processing [12][13][14][15][16][17] , novel forms of spectroscopy 18,19 , and the generation of non-classical states of light 20 . These experimental results have spurred further theoretical developments to understand how the Raman process leads to photonic correlations mediated by a phononic excitation [21][22][23][24] , how the experimental geometry impacts the photon statistics of the Stokes field 25 , and how the coupling of a Raman-active mode to a nanocavity modifies the dynamics of the system [26][27][28] .…”

Continuous-wave frequency upconversion with a molecular optomechanical nanocavity

“…In a different approach, modulations on terahertz waves have been read out optically through a megahertz-frequency mechanical resonator ( 22 ). Molecular oscillators constitute a new frontier in cavity optomechanics ( 23 , 24 ) because they enable multi-terahertz resonant frequencies and room temperature quantum coherent operation ( 25 ). Moreover, they can be coupled to plasmonic nanocavities with deep-subwavelength mode volumes, thereby enabling optomechanical coupling rates in excess of 1 THz ( 26 ).…”