*These authors contributed equally to this work. SUPPORTING INFORMATION:Coupled systems composed of asymmetric resonator elements have symmetric and antisymmetric resonances. In the manuscript, only the antisymmetric resonances are reported for the SRR-bar and ACSRR cases, as the amount of tuning is larger and more strongly dependent on the coupling distance than for the symmetric resonance. In Figure S1, the wavelength range is extended in order to show how both the symmetric and the antisymmetric mode are affected by the sample strain. In the case of the SRR-bar, the symmetric mode, which is largely due to the nanowire resonance, is almost completely unaffected by changing the coupling distance with the other resonator. This was discussed in greater detail in previous work 1 .

Metamaterials can be designed to operate at frequencies from the visible to the mid-IR, making these structures useful for both refractive index sensing and surface-enhanced infrared absorption spectroscopy. Here we investigate how the mechanical deformation of compliant metamaterials can be used to create new types of tunable sensing surfaces. For split ring resonator based metamaterials on polydimethylsiloxane we demonstrate refractive index sensing with figures of merit of up to 10.1. Given the tunability of the resonance of these structures through the infrared after fabrication, they are well suited for detection of the absorption signal of many typical vibrational modes. The results highlight the promise of postfabrication tunable sensors and the potential for integration.

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The on-chip generation of nonclassical states of light is a key requirement for future optical quantum hardware. In solid-state cavity quantum electrodynamics, such nonclassical light can be generated from self-assembled quantum dots strongly coupled to photonic crystal cavities. Their anharmonic strong lightmatter interaction results in large optical nonlinearities at the single photon level, where the admission of a single photon into the cavity may enhance (photon tunneling) or diminish (photon blockade) the probability for a second photon to enter the cavity. Here, we demonstrate that detuning the cavity and quantum-dot resonances enables the generation of high-purity nonclassical light from strongly coupled systems. For specific detunings we show that not only the purity but also the efficiency of single-photon generation increases significantly, making high-quality single-photon generation by photon blockade possible with current state-of-the-art samples. [7] or epitaxially grown photonic nanowires [8] for enhanced light off-chip extraction efficiency. On the other hand, photonic crystal cavities provide a promising on-chip route toward optoelectronic integration of QDs due to the established set of associated integrated waveguide and detector structures [9,10]. Such structures will be able to exploit strong light-matter coupling with QDs for the generation of a variety of on-chip nonclassical light states by various quantum-electrodynamical (QED) methods, and recent exotic proposals have even explored the possibility of releasing energy exclusively in bundles of n photons [11]. The phenomena of photon tunneling and photon blockade in strongly coupled systems have been experimentally demonstrated both for the case of the QD on resonance [12][13][14] and near resonance [15] with the cavity (and likewise, only for resonant atom-cavity system [16]). However, in the case of large detuning these effects have only been investigated theoretically [17].In this Letter, we demonstrate the feasibility of performing photon blockade at significant detuning, and indeed the importance of doing so for high-purity and highefficiency operation. We show that by detuning the QD and cavity resonances while operating in the photonblockade regime, the second-order autocorrelation function [g ð2Þ ð0Þ] of the light transmitted through the cavity decreases from g ð2Þ ð0Þ ¼ 0.9 AE 0.05 to g ð2Þ ð0Þ ¼ 0.29 AE 0.04. Simulations of the second-and third-order autocorrelation functions for our system are in excellent agreement with the measurements, and they reveal that not only does the quality of the single photon stream increase, but that the absolute probability of obtaining a single photon increases by a factor of ∼2. Furthermore, we show that the values we obtain for g ð2Þ ð0Þ are only limited by the system parameters (QD-cavity field coupling strength g and cavity field decay rate κ), and that high-quality single-photon emission is within reach for current state-of-the-art samples for specific cavity and QD detunings.The sample i...

Quantum emitters are an integral component for a broad range of quantum technologies, including quantum communication, quantum repeaters, and linear optical quantum computation. Solid-state color centers are promising candidates for scalable quantum optics due to their long coherence time and small inhomogeneous broadening. However, once excited, color centers often decay through phonon-assisted processes, limiting the efficiency of single-photon generation and photon-mediated entanglement generation. Herein, we demonstrate strong enhancement of spontaneous emission rate of a single silicon-vacancy center in diamond embedded within a monolithic optical cavity, reaching a regime in which the excited-state lifetime is dominated by spontaneous emission into the cavity mode. We observe 10-fold lifetime reduction and 42-fold enhancement in emission intensity when the cavity is tuned into resonance with the optical transition of a single silicon-vacancy center, corresponding to 90% of the excited-state energy decay occurring through spontaneous emission into the cavity mode. We also demonstrate the largest coupling strength (g/2π = 4.9 ± 0.3 GHz) and cooperativity (C = 1.4) to date for color-center-based cavity quantum electrodynamics systems, bringing the system closer to the strong coupling regime.