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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.

-In this study, we investigate the phonon antibunching effect in a coupled nonlinear micro/nanoelectromechanical system (MEMS/NEMS) resonator at a finite temperature. In the weak driving limit, the optimal condition for phonon antibunching is given by solving the stationary Liouville-Von Neumann master equation. We show that at low temperature, the phonon antibunching effect occurs in the regime of weak nonlinearity and mechanical coupling, which is confirmed by analytical and numerical solutions. We also find that thermal noise can degrade or even destroy the antibunching effect for different mechanical coupling strengths. Furthermore, a transition from strong antibunching to bunching for phonon correlation has been observed in the temperature domain. Finally, we find that a suitably strong driving in the finite-temperature case would help to preserve an optimal phonon correlation against thermal noise.Introduction. -Quantum state transfer and storage are crucial in quantum information processing. To date, the photon has been the information carrier most commonly used to transfer and store quantum information, and it has the advantage of high velocity, robustness to different environments, and good integrability. However, phonons, which are vibrational modes of mechanical resonators, can be maintained for a very long time before being eventually damped, and they have the ability to interact with a wide range of quantum systems, such as electric, magnetic, and optical systems. Therefore, phonons also have promising potential as quantum information carriers [1][2][3].In quantum phononic networks, the nonclassical states of phonons or of a single phonon are important elements. Many methods to prepare nonclassical states of phonons or a single phonon have been proposed. For example, a single-phonon Fock state is prepared by two-phonon damping [4], a non-Gaussian state of a mechanical resonator is generated by performing measurements [5], and a single phonon is produced by the heralded measurement of the Stokes photon in cavity optomechanics [6,7].

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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 exits 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) is completely suppressed.

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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.