Resolved-Sideband Cooling of a Levitated Nanoparticle in the Presence of Laser Phase Noise

Abstract

We investigate the influence of laser phase noise heating on resolved sideband cooling in the context of cooling the center-of-mass motion of a levitated nanoparticle in a high-finesse cavity. Although phase noise heating is not a fundamental physical constraint, the regime where it becomes the main limitation in Levitodynamics has so far been unexplored and hence embodies from this point forward the main obstacle in reaching the motional ground state of levitated mesoscopic objects with resolved sideband cooling. We reach minimal center-of-mass temperatures comparable to Tmin = 10mK at a pressure of p = 3 × 10 −7 mbar, solely limited by phase noise. Finally we present possible strategies towards motional ground state cooling in the presence of phase noise.

Strong optomechanical coupling at room temperature by coherent scattering

“…In CS, scattering events from the detuned trapping field, locked at Δ, populate the cavity. This contrasts the approach of actively driving the cavity 3 , 7 , 24 . A particle in free space, solely interacting with the trapping light, Raman scatters photons into free space and the energy difference between incident and emitted light equals ± ℏ Ω m with m = x , y , z .…”

“…The former one gives rise to the optomechanical coupling by CS, and the latter to the coupling achieved by actively driving the cavity. The term gives rise to the trapping potential, while the term causes recoil heating 36 , 41 , which can be neglected for the moderate vacuum conditions presented here 7 , 41 . The remaining two terms can be safely neglected according to ref.…”

“…The optical coupling rate Γ opt depends additionally on the trap detuning Δ and is maximised at Δ = − Ω m to (refs. 7 [, 12 ). While P t and Δ only influence the magnitude of the coupling strength, y 0 and θ change also the nature of the coupling from 1D to potentially 3D 36 .…”

“…Recently, the centre-of-mass motion of a levitated particle has successfully been 3D cooled employing coherent scattering (CS) 8 , 23 . Cooling with CS is less sensitive to phase noise heating than actively driving the cavity 7 , 24 , because optimal coupling takes place at the intensity node. Lately, this has enabled phonon occupation numbers of less than one 9 .…”

“…aser cooling has revolutionised our understanding of atoms, ions and molecules. Lately, after a decade of experimental and theoretical efforts employing the same techniques [1][2][3][4][5][6][7][8] , the motional ground state of levitated silica nanoparticles at room temperature has been reported 9 . While this represents an important milestone towards the creation of mesoscopic quantum objects, coherent quantum control of levitated nanoparticles 10,11 still remains elusive.…”