Fig. 1. Cooling technologies for realizing quantum ground states. (a) Sideband cooling^[21]; (b) laser cooling^[8]; (c) active feedback^[25]; (d) compressed light^[26]

Fig. 2. Studies of acoustic quantum states. (a) Phonon count in optomechanical crystal^[37]; (b) acoustic quantum state in eardrum resonator^[38]; (c) manipulation of coherent phonon in nanoresonator^[40]

Fig. 3. Regulations of acoustic quantum states: entanglement state. (a) Optomechanical entanglement scheme^[41]; (b) distant entanglement scheme^[43]; (c) acoustic quantum state coupled with microwave photon in superconducting eardrum^[44]; (d) non-classical correlation of photon and phonon in one-dimensional optomechanical crystal^[45]

Fig. 4. Regulations of acoustic quantum states: squeezed state. (a) Quadrature squeezing of acoustic quantum state^[51]; (b) quantum squeezing state in a mechanical resonator^[53]; (c) quantum squeezing state via detuning-switched driving^[55]; (d) quantum squeezing resonator with ms quantum decoherence time^[56]

Fig. 5. Regulations of acoustic quantum states: Fock state. (a) Preparing of phonon Fock state through a non-Gaussian state light field^[57]; (b) preparing of a phonon Fock states through parametric down-conversion^[58]; (c) phonon blockade in atom-photon-phonon hybrid system^[61]; (d) non-classical correlation between single phonon states and single photons in the SiN eardrum resonator^[62]

Fig. 6. Mode locking of acoustic quantum states. (a) Self-excited oscillation of external radiation pressure^[65]; (b) injection locking^[66]; (c) multimode competition^[69]; (d) dual-mode locking^[70]

Fig. 7. Microwave-optical conversion. (a) Microwave-optical conversion of the eardrum system^[78]; (b) microwave-optical conversion of BAR system^[81]; (c) microwave-phonon-photon coupling in one-dimensional optomechanical crystal based on AlN^[83]; (d) conversion of superconducting qubits to communication optics^[84]; (e) microwave-optical conversion based on lithium niobate^[87]; (f) microwave-phonon-photon coupling based on GaAs^[89]; (g) microwave-optical conversion based on GaAs^[90]; (h) microwave-optical conversion based on GaP^[91]

Fig. 8. Phonon transmission. (a) Array of optomechanical crystal cavity (snowflake shape)^[93]; (b) array of suspended microspheres^[94]; (c) array of optomechanical crystal cavity (snowflake microporous shape)^[95]

Fig. 9. Quantum storage. (a) One-dimensional resonator-optical cavity coupling system^[98]; (b) diamond microdisk system^[100]; (c) one-dimensional optomechanical crystal system^[101]

Fig. 10. Applications of optomechanical system in quantum precision measurement. (a) One-dimensional optomechanical crystal accelerometer^[102]; (b) on-chip optomechanical system accelerometer^[105]; (c) gyroscope for electro-opto-mechanical system^[106]; (d) gyroscope of microsphere shell combined with ring resonator^[108]

Fig. 11. Basic physics explorations of optical force systems. (a) Schematic diagram of LIGO structure^[110]; (b) gravitational force detection between non-classical mechanical oscillators^[111]; (c) design of instruments for direct measurement of light dark matter^[113]; (d) quantum ground state cooling using measurement-based feedback and a JTWPA^[115]

Fig. 12. Hybrid systems. (a) Tunable F-P cavity based on ultracold atom^[120]; (b) optomechanical system formed by ultracold atom and thin film^[121]; (c) optomechanical regulation of NV color center^[122]; (d) NV color center in diamond optomechanical crystal^[125]