Zhi-Wei Wang

Spatial mode properties of plasmon-assisted transmission

Orbital angular momentum of photons is explored to study the spatial mode properties of the plasmon-assisted transmission process. We found that photons carrying different orbital angular momenta have different transmission efficiencies, while the coherence between these spatial modes can be preserved.

Influence of unsymmetrical periodicity on extraordinary transmission through periodic arrays of subwavelength holes

Quadrate hole array is explored to study the influence of unsymmetrical periodicity on extraordinary optical transmission through periodic arrays of subwavelength holes. It is found that the transmission efficiency of light and the ratio between transmission efficiencies of horizontal and vertical polarized light can be continuously tuned by rotating the quadrate hole array. The authors can calculate out the transmission spectra (including the heights and locations of peaks) for any rotation angle θ with a simple theoretical model.

Polarization properties of subwavelength hole arrays consisting of rectangular holes

The influence of hole shape on extraordinary optical transmission was investigated using hole arrays consisting of rectangular holes with different aspect ratios. It was found that the transmission could be tuned continuously by rotating the hole array. Furthermore, a phase was generated in this process, and linear polarization states could be changed to elliptical polarization states. This phase was correlated with the aspect ratio of the holes. An intuitional model was presented to explain these results.

Experimental entanglement quantification and verification via uncertainty relations

We report on experimental studies on entanglement quantification and verification based on uncertainty relations for systems consisting of two qubits. The new proposed measure is shown to be invariant under local unitary transformations, by which entanglement quantification is implemented for two-qubit pure states. The nonlocal uncertainty relations for two-qubit pure states are also used for entanglement verification which serves as a basic proposition and promise to be a good choice for verification of multipartite entanglement.

Remote control of extraordinary transmission through subwavelength hole arrays

For pairs of entangled photons, each seems to know about the state of the other. Using this property of quantum entanglement, we can remotely control the extraordinary optical transmission through subwavelength holes in a metal plate. Our method can also be used for entanglement distillation.

Removal of surface plasmon polariton eigenmodes degeneracy

The effect of the tilt angle of a metal film on the transmissivity of subwavelength holes in optically thick metal film is investigated. We found that the transmission efficiency can be highly dependent on the tilt angle. It is also found that when the input photons are not polarized along the eigenmode directions of surface plasmon polariton, a birefringent phenomenon is observed when a periodic array of subwavelength holes is tilted. Linear polarization states can be changed to elliptical polarization states, and a phase can be added between two eigenmodes. The phase is changed with the tilt angle. A model based on surface plasmon polariton eigenmodes degeneracy is presented to explain these experimental results.

Interference of surface plasmon polaritons controlled by the phase of incident light

Interference patterns of surface plasmon polaritons(SPPs) are observed in the extraordinary optical transmission through subwavelength holes in optically thick metal plate. It is found that the phase of incident light can be transferred to SPPs. We can control the destructive and constructive interference of SPPs by modulating the relative phase between two incident beams. Using a slightly displaced Mach-Zehnder interferometer, we also observe a SPPs interference pattern composed of bright and dark stripes.

Manipulating quantum states with aspheric lenses

Abstract We present an experimental demonstration to manipulate the width and position of the down-converted beam waist. Our results can be used to engineer the two-photon orbital angular momentum (OAM) entangled states (such as concentrating OAM entangled states) and generate Hermite–Gaussian (HG) modes entangled states.

Linear optical implementation of perfect discrimination between single-bit unitary operations

Discrimination of unitary operations is a fundamental task of quantum information. Assisted by linear optical elements, we experimentally demonstrate perfect discrimination between single-bit unitary operations using the sequential scheme which is proved by Duan et al (Phys. Rev. Lett. 2007 98 100503). We also make a comparison with another perfect discrimination scheme called the parallel scheme. The complexity and resource consumed are analysed.

Entanglement witness measurement for two-qubit states by optical interference

We present a novel interferometer to directly implement entanglement witness measurement. This is optimal and avoids the complex task to decompose witness into local projectors. The interferometer is based on a hybrid realization of controlled-SWAP gate. We also demonstrate entanglement-witness for simple cases experimentally.