Antibunched single-photon/photon-pair emission with coupled Jaynes-Cummings model.

Herein, we propose a coupled Jaynes-Cummings model for the preparation of strong antibunched single photons and antibunched correlated photon pairs. Using the effective Hamiltonian method, we obtained the expression for the correlation function and then presented the optimal conditions for conventional/unconventional photon blockade. The results showed that on one hand, an intersection point exists between conventional photon blockade and unconventional photon blockade and that the performance of the single photon at the intersection point is better. On the other hand, under the condition of unconventional photon blockade, the photons produced by each Jaynes-Cummings system are strongly correlated with each other.

Sub-femto-Newton sensing torsion pendulum for detection of light force.

Mechanical oscillators are widely used in many fields of physics, including ultrahigh precision measurements, gravity experiments, and optical mechanical systems. A sub-gram-scale silicon wafer is suspended by a tungsten wire with a diameter of 8 µm, forming a torsion pendulum to detect the laser radiation pressure. We demonstrate the application of a low-frequency, highly sensitive torsion pendulum for the measurement of light forces. In the feedback cooling state, the system exhibits a force sensitivity at the end of the pendulum close to 0.1 fN, approaches the thermal noise limit, and reaches the detection level of the laser radiation pressure of 60 nW.

Coherent feedback induced transparency.

We propose a light transparency effect induced by coherent feedback. By studying a system comprising a linear optical cavity controlled by a linear coherent feedback loop, we show that the optical signal field passing through the system cavity exhibits novel transparency behaviors. Unidirectional coupling between the system and its feedback control loop enables the group velocity and transmission rate to be tuned separately, thus maintaining the unity transmission rate when the group velocity is significantly suppressed. Furthermore, we demonstrate that simply applying a certain phase shift to the output of the system cavity and feeding it back into the system can induce perfect transmission. Our proposal offers a simple and effective way to control light transmission and group velocity using only linear optics elements.

Improvement for Testing the Gravitational Inverse-Square Law at the Submillimeter Range.

We improve the test of the gravitational inverse-square law at the submillimeter range by suppressing the vibration of the electrostatic shielding membrane to reduce the disturbance coupled from the residual surface potential. The result shows that, at a 95% confidence level, the gravitational inverse-square law holds (|α|≤1) down to a length scale λ=48 µm. This work establishes the strongest bound on the magnitude α of the Yukawa violation in the range of 40-350 µm, and improves the previous bounds by up to a factor of 3 at the length scale λ≈70 µm. Furthermore, the constraints on the power-law potentials are improved by about a factor of 2 for k=4 and 5.

Pulse-regulated single-photon generation via quantum interference in a χ(2) nonlinear nanocavity.

A scalable on-chip single-photon source at telecommunications wavelengths is an essential component of quantum communication networks. In this work, we numerically construct a pulse-regulated single-photon source based on an optical parametric amplifier in a nanocavity. Under the condition of pulsed excitation, we study the photon statistics of the source using the Monte Carlo wave-function method. The results show that there exists an optimum excitation pulse width for generating high-purity single photons, while the source brightness increases monotonically with increasing excitation pulse width. More importantly, our system can be operated resonantly, and we show that in this case the oscillations in g(2)(0) are completely suppressed.

Null test of Newtonian inverse-square law at submillimeter range with a dual-modulation torsion pendulum.

A null experimental test of the Newtonian inverse-square law at submillimeter range using a torsion pendulum was presented. Under the dual modulations of both the expected signal and the gravitational torque for calibration, our data concluded with 95% confidence that no new forces were observed and any gravitational-strength Yukawa forces (|alpha|>or=1) must have a length scale lambda<66 microm, agreeing well with the latest result of the Eöt-wash group. Our result sets a unification energy scale of M*>or=2.8 TeV/c2 for the two compactified extra space dimensions with the same size R*<47 microm.