Nonlinear Quantum Optomechanics via Individual Intrinsic Two-Level Defects

Abstract

We propose to use the intrinsic two-level system (TLS) defect states found naturally in integrated optomechanical devices for exploring cavity QED-like phenomena with localized phonons. The Jaynes-Cummings-type interaction between TLS and mechanics can reach the strong coupling regime for existing nano-optomechanical systems, observable via clear signatures in the optomechanical output spectrum. These signatures persist even at finite temperature, and we derive an explicit expression for the temperature at which they vanish. Further, the ability to drive the defect with a microwave field allows for realization of phonon blockade, and the available controls are sufficient to deterministically prepare non-classical states of the mechanical resonator.Introduction.-Cavity optomechanics [1-3] has enabled the preparation of mechanical resonators in states of low phonon occupation via optomechanical (OM) sideband cooling [4][5][6][7][8][9], and to observe their quantum coherent interaction with light [9]. Further, OM systems have enabled displacement detection at or even below the standard quantum limit [10][11][12], thereby complementing other mechanics-based sensing applications [13,14]. They have also been proposed for creating macroscopic quantum superpositions [15] as well as for applications in quantum information [16,17]. However, in experiments carried out so far, the interaction between mechanical oscillator and cavity field is effectively linear, while one of the major challenges in the field is to realize non-linearities at the single phonon level. For example, the intrinsic OM radiation pressure non-linearity is predicted to enable the generation of non-classical states of light and mechanics [18,19], provided that the singlephoton coupling rate exceeds the mechanical frequency and the cavity decay rate. In multi-mode OM systems, the same non-linearity can be exploited more easily and it has been proposed to use it for enhanced readout [20] and quantum information processing [21].Here we propose an alternative route to render the dynamics of the mechanical oscillator nonlinear at the single quantum level: using its natural coupling to intrinsic structural two-level system (TLS) defects and thereby alleviating the need to functionalize the system [see Fig. 1(a)]. Ensembles of TLS defects were first studied in the context of the anomalous and universal low temperature properties of glasses [22][23][24][25][26], where they arise from frustration. In experiments involving Josephson junctions, individual TLSs with transition energies distributed well into the GHz regime were observed and studied for their role in decoherence [27]. Nevertheless, their comparatively long coherence times, and their ability to strongly couple to Josephson junctions via the electric dipole moment have enabled a TLS quantum memory [28]. In the same context, the influence of strain on TLSs has been probed recently [29]. However, in the OM setting, TLS ensembles have mainly been studied

Optomechanical analog of two-color electromagnetically induced transparency: Photon transmission through an optomechanical device with a two-level system

“…1, we study a general theoretical model of a hybrid device in which a two-level system is coupled to the mechanical resonator of an optomechanical system [79]. Figure 1 can also describe a system, in which a single-mode cavity field is coupled to a mechanical resonator which interacts with a two-level system as in Refs.…”

“…Then, if there exists a defect in the mechanical resonator of an optomechanical system, then a threebody hybrid system composed of a mechanical mode, a twolevel defect, and a cavity field can be formed. The intrinsic two-level defects in the mechanical resonator can affect the ground-state cooling of the mechanical mode and the nonlinear properties of an optomechanical system [28,79]. As mentioned above, this kind of hybrid systems can also be realized by an extra capacitive coupling of a superconducting qubit to the mechanical resonator of an optomechanical system [32].…”

Single-Polariton Optomechanics

“…When the bath of the system is at very low temperatures, the hybrid configuration leads to non-classical statistics of the mechanical motion leading to negative values of its Wigner function and emission of single phonons with strong antibunching. These concepts could be tested on a large set of experimental platforms spanning from a real single atom trapped in a macroscopic optomechanical FabryPerot cavity resonator, to diamond resonators embedding NV centers, defect centers in silica toroids [23], or semiconductor optomechanical systems with built-in artificial atoms. Of peculiar interest are miniature GalliumArsenide optomechanical resonators combining strong optomechanical [14,15] with cavity QED couplings [24], and superconducting systems where strong coupling circuit QED and quantum control of GHz mechanical motion have been already demonstrated [7].…”

Controlling photon transport in the single-photon weak-coupling regime of cavity optomechanics

“…The nonlinear interaction between optical and mechanical modes arising from radiation pressure force in optomechanical (OM) systems exhibit a lot of interesting nonlinear effects such as photon (phonon) blockade [16,17], optomechanical induced transparency [18,19] and Kerr nonlinearity [20,21]. Cavity optomechanics has received significant attention both in fundamental experiments [22,23] and sensing applications [24,25].…”