Motivated by the great advances in the enhancement of the optomechanical coupling at the level of single photons,
[23-26] much recent interest has been paid to the study of the single-photon strong-coupling regime of cavity optomechanics.
[27-37] The optomechanical interaction in this regime can provide a platform to study the observable optomechanical effects at the level of single photons. In particular, fruitful achievements have been obtained in the studies of various effects in linear optomechanical coupling at the few- and even single-photon levels.
[27-29,32,38-39] For example, the oscillating boundary of the cavity will induce a Kerr-type optical nonlinearity and this nonlinearity has been exploited to realize photon blockade effect in the linear optomechanical cavity.
[27,32] The emission spectrum of the optomechanical cavity has been studied in both the continuous-wave and wavepacket driving cases.
[28-29] It has been found that the phonon sideband peaks appear in the spectrum when the system works in both the single-photon strong-coupling and resolved-sideband regimes. The conditional displacement dynamics of a single photon in optomechanics has been suggested to generate quantum superposition of distinct mechanical states.
[38-39] In addition, some applications of the optomechanical interactions at the single-photon level have been proposed. These applications include the spectrometric reconstruction of the mechanical states
[40] and the spectrometric detection of weak classical forces.
[41]