Applied Physics
Optomechanical systems typically consist of a mechanical oscillator or cantilever that can be driven by the optical radiation pressure of light. The light can either amplify the motion of the cantilever or be used to reduce the amount of vibration and effectively cool it. Recent work has demonstrated cooling to the extent that the number of vibrations, or phonons, in an oscillator can be quantized, even reaching the quantum-mechanical ground. Galland et al. introduce a method to introduce a single phonon into their mechanical oscillator. Starting off in the quantum-mechanical ground, they pump the system with a laser pulse that generates an entangled phonon-photon pair. Detection of the photon then heralds that a single-phonon state has been induced into the oscillator. The ability to deterministically control the number of vibrational quanta in such an optomechanical system has important implications for the likes of quantum information processing and quantum enhanced sensing applications.
Phys. Rev. Lett. 112 , 143602 (2014).
A single quantum of excitation of a mechanical oscillator is a textbook example of the principles of quantum physics. Mechanical oscillators, despite their pervasive presence in nature and modern technology, do not generically exist in an excited Fock state. In the past few years, careful isolation of GHz-frequency nano-scale oscillators has allowed experimenters to prepare such states at milli-Kelvin temperatures. These developments illustrate the tension between the basic predictions of quantum mechanics that should apply to all mechanical oscillators existing even at ambient conditions, and the complex experiments in extreme conditions required to observe those predictions. We resolve the tension by creating a single Fock state of a vibration mode of a crystal at room temperature using a technique that can be applied to any Raman-active system. After exciting a bulk diamond with a femtosecond laser pulse and detecting a Stokes-shifted photon, the 40~THz Raman-active internal vibrational mode is prepared in the Fock state
∣1> with
98.5% probability. The vibrational state is read out by a subsequent pulse, which when subjected to a Hanbury-Brown-Twiss intensity correlation measurement reveals the sub-Poisson number statistics of the vibrational mode. By controlling the delay between the two pulses we are able to witness the decay of the vibrational Fock state over its
3.9 ps lifetime at room temperature. Our technique is agnostic to specific selection rules, and should thus be applicable to any Raman-active medium, opening a new generic approach to the experimental study of quantum effects related to vibrational degrees of freedom in molecules and solid-state systems.
We propose a setup allowing to entangle two directly non-interacting radiation modes applying four sequential pulsed quantum resonant interactions with a noisy vibrational mode of a mechanical oscillator which plays the role of the mediator. We analyze Gaussian entanglement of the radiation modes generated by the transducer and confirm that the noisy mechanical mode can mediate generation of entanglement. The entanglement, however, is limited if the interaction gains are not individually optimized. We prove the robustness of the transducer to optical losses and the influence of the mechanical bath and propose the ways to achieve maximal performance through the individual optimization.