Direct Measurement And Extraordinary Optical Transmission Of Continuous-variable Entanglement

Quantum entanglement is one of the most incredible and the most fascinating things in quantum mechanics. Quantum information and quantum computing, based on quantum entanglement, have been paid much attention by researchers, and remarkable achievements have been made in these fields. Entanglement between quadrature components of light fields is known as continuous-variable entanglement as the quadrature component has a continuous spectrum. The continuous-variable entanglement is an important research direction of quantum entanglement. An optical parametric amplifier based on the second-order nonlinear optical process is one of the main approaches to produce continuous-variable entangled states. As the signal and idler beams emitting from the nondegenerate optical parametric amplifier (NOPA) with seed injected are EPR entangled, the NOPA is a reliable source of continuous-variable entanglement.Plasmon polariton is a hybrid mode coupled by light field and electron oscillation on a metal surface. In recent years, researchers began to pay attention to its quantum properties and a new research hotspot has emerged. Subwavelength hole arrays in metal films have the phenomenon of extraordinary optical transmission (EOT) due to effect of plasmon polariton. Extraordinary optical transmission of entanglement has become a gap to reveal the quantum properties of plasmon polariton.By means of a continuous-variable entanglement source in our laboratory, this thesis focuses on entanglement measurement and extraordinary optical transmission of entanglement. The main contents are as follows.1. We propose a new direct Bell-state measurement scheme using an unbalanced Mach-Zehnder interferometer (UMZI). The UMZI is constructed by two single-mode optical fibers with lengths of 2 m and 50 m. Quantum correlation between the twin beams from the NOPA operating in an amplification mode is measured by this UMZI. The measured correlation variances of amplitude difference and phase sum are 1.79 dB and 1.62 dB below the shot noise limit, respectively. This method can directly acquire the quantum correlations of amplitude quadratures and phase quadratures simultaneously. Difficulties to measure twin beams with correlation of amplitude quadratures and anticorrelation of phase quadratures are overcome.2. Extraordinary optical transmission of continuous-variable entanglement is studied. We use focused ion beam to fabricate a gold film with hole arrays of hexagonal symmetry and obtain a transmittance of 75%. The continuous-variable entanglements are first demonstrated to survive after a photon-plasmon-photon conversion process. The incidence entangled beams with correlation variances of 2.7 dB amplitude sum and 2.1 dB phase difference are still in entanglement with 2.2 dB amplitude sum and 1.6 dB phase difference after the hole arrays. We also use a feedback-control technique to utilize the reflected light from the metal plate and reduce entanglement degradation caused by loss.3. We set up an experimental system to perform quantum tomography and make some initial research on the process of extraordinary optical transmission. The process tomography of a hole array sample with a transmittance of 66% is build and the Fidelity is 99.9%. It suggests that taking the process of EOT as loss is reasonable. We are analysing the changes of phase in EOT process.