Performance and limits of feedback cooling methods for levitated oscillators: A direct comparison

Abstract

Cooling the center-of-mass motion is an important tool for levitated optomechanical systems, but it is often not clear which method can practically reach lower temperatures for a particular experiment. We directly compare the parametric and velocity feedback damping methods, which are used extensively for cooling the motion of single trapped particles in a range of traps. By performing experiments on the same particle, and with the same detection system, we demonstrate that velocity damping cools the oscillator to a temperature an order of magnitude lower and is more resilient to imperfect experimental conditions. We show that these results are consistent with analytical limits as well as numerical simulations that include experimental noise.

Equilibrium stochastic delay processes

“…In table 1, we summarize relations between the three interpretations and the definitions of the corresponding forces. While the purpose of this paper is to primarily discuss equilibrium delay processes theoretically, appendix B offers some suggestions regarding possible experimental realizations for Markovian thermal reservoirs (described by white noise) using state-of-the-art experimental setups similar to those in [39,[67][68][69]. In the following, we take Boltzmann's constant k B as our unit of entropy.…”

“…introduced in table 1(C), are in good agreement with measurements performed both in the underdamped and overdamped regime. An example of the former is the velocity damping experiments, where an optomechanically trapped particle diffusing in a dilute gas is cooled using velocity feedback [38,39].…”

“…However, the small-τ expansion (32) leads to T eff < T 0 and thus it suggests a positive value of QM . 4 and driven with a time symmetric protocol (39) for the potential (36). The remaining panels show the function (41) for NEFB (b), EFB (c), and EQ (d).…”

“…Test of the Crooks fluctuation theorem. (a) Probability densities for work for NEFB, EFB and EQ processes departing from the stationary state of figure4and driven with a time symmetric protocol(39) for the potential(36). The remaining panels show the function(41) for NEFB (b), EFB (c), and EQ (d).…”

Cooling through parametric modulations and phase-preserving quantum measurements

“…As a result, the system can only be operated at parametric resonance over short time-scales and with weak driving strengths, which is what we assume for the cooling protocol. A similar issue arises when solving the dynamics of classical oscillators with a time-modulated potential [43]. We discuss this further in Supplemental Note 2.…”