Mark C. Kuzyk

Optomechanical Dark Mode

Inducing a Quiet Space The interaction between light and matter forms the foundation of many applications in communication and sensing, as well as provides insights into fundamental quantum-level processes. Optical coupling of a mechanical system can be used to study these processes. However, because the mechanical oscillator is unavoidably coupled to its environment, thermal noise can spoil the sensitivity of the optomechanical coupling. Dong et al. (p. 1609, published online 15 November) exploit the ability to form a mechanical “dark state” that can effectively isolate the mechanical system from thermal-induced noise. The formation of such a noise-free zone may provide a simpler route to probe quantum optomechanical systems that circumvents the need to cool the oscillator to its quantum limit where all thermal motion is frozen out. The formation of a mechanical dark mode can be used to isolate an optomechanical system from thermal noise. Thermal mechanical motion hinders the use of a mechanical system in applications such as quantum information processing. Whereas the thermal motion can be overcome by cooling a mechanical oscillator to its motional ground state, an alternative approach is to exploit the use of a mechanically dark mode that can protect the system from mechanical dissipation. We have realized such a dark mode by coupling two optical modes in a silica resonator to one of its mechanical breathing modes in the regime of weak optomechanical coupling. The dark mode, which is a superposition of the two optical modes and is decoupled from the mechanical oscillator, can still mediate an effective optomechanical coupling between the two optical modes. We show that the formation of the dark mode enables the transfer of optical fields between the two optical modes. Optomechanical dark mode opens the possibility of using mechanically mediated coupling in quantum applications without cooling the mechanical oscillator to its motional ground state.

Storing optical information as a mechanical excitation in a silica optomechanical resonator.

We report the experimental demonstration of storing optical information as a mechanical excitation in a silica optomechanical resonator. We use writing and readout laser pulses tuned to one mechanical frequency below an optical cavity resonance to control the coupling between the mechanical displacement and the optical field at the cavity resonance. The writing pulse maps a signal pulse at the cavity resonance to a mechanical excitation. The readout pulse later converts the mechanical excitation back to an optical pulse. The storage lifetime is determined by the relatively long damping time of the mechanical excitation.

Non-reciprocal Brillouin scattering induced transparency

By exploiting the interaction between light and phonons in a silica microsphere resonator it is possible to generate Brillouin scattering induced transparency, which is akin to electromagnetically induced transparency but for acoustic waves.

Optomechanical light storage in a silica microresonator

Coherent inter-conversion between an optical and a mechanical excitation in an optomechanical resonator can be used for the storage of an optical pulse as an excitation in a mechanical oscillator. This optomechanical light storage is enabled by external writing and readout pulses at one mechanical frequency below the optical resonance. In this paper, we expand an earlier experimental study [Phys. Rev. Lett. 107, 133601 (2011)] on storing an optical pulse as a radial breathing mode in a silica microsphere. We show that the heterodyne beating between a readout pulse and the corresponding retrieved pulse features a periodic oscillation with a well-defined phase and with the beating period given by the mechanical frequency, demonstrating directly the coherent nature of the light storage process. The coherent inter-conversion accelerates with increasing optomechanical coupling rates, providing an effective mechanism for tailoring the temporal profile of the retrieved pulse. Experimental studies on both light storage and optomechanically induced transparency under nearly the same conditions also illustrate the connections between these two closely-related processes.

Generating robust optical entanglement in weak-coupling optomechanical systems

A pulsed scheme for generating robust optical entanglement via the coupling of two optical modes to a mechanical oscillator is proposed. This scheme is inspired by the S{\o}rensen-M{\o}lmer approach for entangling trapped ions in a thermal environment and is based on the use of optical driving pulses that are slightly detuned from the respective sideband resonance. We show that for certain pulse durations, the optomechanical interaction can return the mechanical oscillator to its initial state. The corresponding entanglement generation is robust against thermal mechanical noise in the weak as well as the strong coupling regimes. Significant optical entanglement can be generated in the weak coupling regime, even in the presence of a large thermal phonon occupation.

Controlling multimode optomechanical interactions via interference

We demonstrate optomechanical interference in a multimode system, in which an optical mode couples to two mechanical modes. A phase-dependent excitation-coupling approach is developed, which enables the observation of constructive and destructive optomechanical interferences. The destructive interference prevents the coupling of the mechanical system to the optical mode, suppressing optically-induced mechanical damping. These studies establish optomechanical interference as an essential tool for controlling the interactions between light and mechanical oscillators.

Observation of brillouin scattering induced transparency in a silica microsphere resonator

We experimentally demonstrate induced transparency in silica microsphere resonator using forward Brillouin scattering.

Optomechanical dark mode

Summary form only given. Thermal mechanical motion hinders the use of a mechanical system in applications such as quantum information processing. A straightforward, but technically challenging, approach to overcome the thermal motion is to cool the mechanical oscillator to its motional ground state. An alternative approach, as proposed recently, is to exploit the use of a mechanically-dark mode, which is a special coherent superposition of two optical modes [1, 2]. The cancellation in the mechanical coupling induced by the superposition decouples the dark mode from the mechanical oscillator. The formation of the dark mode, however, also induces a conversion of the optical field from one optical mode to the other. This type of mechanically-mediated coupling is immune to thermal mechanical motion, providing a promising mechanism for interfacing hybrid quantum systems. Here, we report the experimental demonstration of such a dark mode by coupling two optical modes in a silica resonator to one of its mechanical breathing modes in the regime of weak optomechanical coupling [3].

Optical state transfer via optomechanical dark mode

We demonstrate an optomechanical dark mode that converts fields between two optical modes, but is decoupled from the mechanical oscillator. The dark mode can enable mechanically-mediated quantum-state-transfer, without cooling the mechanical system to its ground state.

Generating robust optical entanglement via optomechanical coupling

A pulsed scheme for generating two-mode squeezed light via the coupling of two optical modes to a mechanical oscillator in an optomechanical system is proposed. The scheme can be robust against thermal mechanical motion.