Systems of coupled mechanical resonators are useful for quantum information processing and fundamental tests of physics. Direct coupling is only possible with resonators of very similar frequency, but by using an intermediary optical mode, non-degenerate modes can interact and be independently controlled in a single optical cavity. Here we demonstrate coherent optomechanical state swapping between two spatially and frequency separated resonators with a mass ratio of 4. We find that, by using two laser beams far detuned from an optical cavity resonance, efficient state transfer is possible. Although the demonstration is classical, the same technique can be used to generate entanglement between oscillators in the quantum regime.

Two major challenges in the development of optomechanical devices are achieving a low mechanical and optical loss rate and vibration isolation from the environment. We address both issues by fabricating trampoline resonators made from low pressure chemical vapor deposition (LPCVD) Si3N4 with a distributed bragg reflector (DBR) mirror. We design a nested double resonator structure with 80 dB of mechanical isolation from the mounting surface at the inner resonator frequency, and we demonstrate up to 45 dB of isolation at lower frequencies in agreement with the design. We reliably fabricate devices with mechanical quality factors of around 400,000 at room temperature. In addition these devices were used to form optical cavities with finesse up to 181,000 ± 1,000. These promising parameters will enable experiments in the quantum regime with macroscopic mechanical resonators.In recent years there has been tremendous growth in the field of optomechanics [1, 2]. The interaction of light and mechanical motion has been used to demonstrate such phenomena as ground state cooling of a mechanical resonator [3][4][5], optomechanically induced transparency [6][7][8], and entanglement of a mechanical resonator with an electromagnetic field [9]. Another proposed application of optomechanics is testing the concept of quantum superpositions in large mass systems [10]. All of these experiments require low optical and mechanical loss rates. In this letter we will focus on our efforts to produce a large mass mechanical resonator with both high mechanical and optical quality factor, which can realistically be cooled to its ground state.There are several requirements for the devices to achieve this. The system must be sideband resolved for optical sideband cooling to the ground state [11,12]. A high mechanical quality factor is also necessary to generate a higher cooperativity and a lower mechanical mode temperature for the same cooling laser power. Furthermore, in the quantum regime, the quality factor sets the timescale of environmentally induced decoherence [13], which is crucial for proposed future experiments. Therefore, it is important to eliminate mechanical and optical loss sources.One major source of loss in mechanical systems is clamping loss, which is coupling to external mechanical modes [14][15][16]. As we will show, this is a critical source of loss for Si 3 N 4 trampoline resonators. Several methods of mechanically isolating a device from clamping loss have been demonstrated including phononic crystals [17,18] and low frequency mechanical resonators [19][20][21][22][23]. Due to the large size of phononic crystals at the frequency of our devices (about 250 kHz), we have selected to sur- * Electronic address: mweaver@physics.ucsb.edu † Now at: Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA round our devices with a low frequency outer resonator. We significantly improve on the design of similar devices using silicon optomechanical resonators [24] by using...

Experimental observation of the decoherence of macroscopic objects is of fundamental importance to the study of quantum collapse models and the quantum to classical transition. Optomechanics is a promising field for the study of such models because of its fine control and readout of mechanical motion. Nevertheless, it is challenging to monitor a mechanical superposition state for long enough to investigate this transition. We present a scheme for entangling two mechanical resonators in spatial superposition states such that all quantum information is stored in the mechanical resonators. The scheme is general and applies to any optomechanical system with multiple mechanical modes. By analytic and numeric modeling, we show that the scheme is resilient to experimental imperfections such as incomplete pre-cooling, faulty postselection and inefficient optomechanical coupling. This proposed procedure overcomes limitations of previously proposed schemes that have so far hindered the study of macroscopic quantum dynamics.

In multimode optomechanical systems, the mechanical modes can be coupled via the radiation pressure of the common optical mode, but the fidelity of the state transfer is limited by the optical cavity decay. Here we demonstrate stimulated Raman adiabatic passage (STIRAP) in optomechanics, where the optical mode is not populated during the coherent state transfer between the mechanical modes avoiding this decay channel. We show a state transfer of a coherent mechanical excitation between vibrational modes of a membrane in a high-finesse optical cavity with a transfer efficiency of 86%. Combined with exceptionally high mechanical quality factors, STIRAP between mechanical modes can enable generation, storage, and manipulation of long-lived mechanical quantum states, which is important for quantum information science and for the investigation of macroscopic quantum superpositions.

We demonstrate 128 Gbps/port (8-λ × 16 Gbps/λ) natively error-free transmission across eight optical ports using a 8-port, 8-λ/port WDM remote laser source and a pair of monolithically integrated CMOS optical I/O chiplets with 4.96-5.56 pJ/bit optical Tx+Rx chiplet energy efficiency.