Photon blockade (PB), an effective method of generating antibunching effect, is a critical way to construct a single photon source. The PB effect can be divided into conventional PB effect (CPB) and unconventional PB effect (UPB). Most studies focus on designing systems to successfully enhance CPB or UPB effect individually. However, CPB extremely depends on the nonlinearity strength of the Kerr materials to achieve strong antibunching effect while UPB relies on quantum interference beset with the high probability of the vacuum state. Here, we propose a method to utilize the relevance and complementarity of CPB and UPB to realize these two types simultaneously. We employ a hybrid Kerr nonlinearity two-cavity system. Because of the mutual assistance of two cavities, CPB and UPB can coexist in the system under certain states. In this way, for the same Kerr material, we reduce the value of the second-order correlation function due to CPB by three orders of magnitude without losing the mean photon number due to the presence of UPB, so the advantages of both PB effects are fully reflected in our system, which is a huge performance boost for single photons.

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In recent years, most of the previous studies focused on the perfect absorption and high-efficiency quantum memory of the one-sided system, which ignoring the characteristics of its optical switching contrast. Thus, the performance of all-optical switching and optical transistors is limited. Herein, we propose a localized surface plasmon (LSP) mode-assisted cavity QED system which consists of a Λ-shaped three-level quantum emitter (QE), a metal nanoparticle and a one-sided optical cavity with a fully reflected mirror. In this system, the QE coherently couples to the cavity and LSP mode, respectively, which is manipulated by the control field. As a result, considerable high and stable switch contrast 90% can be achievable due to the strong confined field of LSP mode and perfect absorption of the optical medium. In addition, we obtain a power dependent effect between the control field and the transmitted frequency as a result of the converted dark state. We employ the Heisenberg-Langevin equation and numerical Master equation formalisms to explain high switching, controllable output light and the dark state. Our system introduces an effective method to improve the performance of optical switches based on one-sided system in quantum information storage and quantum communication.

Precise force measurement is critical to probing biological events and physics processes, spanning from molecular motor’s motion to the Casimir effect1 and the detection of gravitational wave2. Yet, despite extensive technology developments, the 3D nanoscale measurement of weak forces in aqueous solutions poses a significant challenge. Techniques that rely on the optically trapped nanoprobe are beset with difficulties, including low light scattering for force measuring and high localization error from their Brownian motion. Here, we report the measurement of the long-distance electrodynamic force on single nanocrystals suspended in aqueous solution with only 11 net charges. To achieve this, we develop an upconversion photonic force microscope that encompasses a diffraction-limited tracking-based force sensing theory and the advance of lanthanide ion resonance force probe3,4. The tracking method is based on neural network empowered super-resolution localization, where the position of force probe is extracted from the optical astigmatism modified point spread functon(PSF), enabling the measurement of trap stiffness for nanoparticles through equipartition theorem with a force sensitivity down to 592.9 attoNewtons (aN), that is, 5 times lower than the reported best sensitivity value5. We further demonstrate that the technology can measure a single nanocrystal's electrophoresis force and zeta potential, experimentally verifying Loeb's empirical relationship. This work offers new opportunities for detecting single-charge dynamics over long-distance and sub-cellular single molecular level biomechanical force.