Qingqing Sun

Quantum lithography with classical light : Generation of arbitrary patterns

Based on our previous scheme [Hemmer et al., Phys. Rev. Lett. 96, 163603 (2006)] we show the procedures to obtain any one- or two-dimensional pattern by multiple exposures. A key modification to the resonance condition is made to achieve subwavelength pattern resolution. The level separation of the substrate does not pose an upper limit to the frequency summation. So the fundamental frequency can be high and the number of Fourier terms can be large, making our scheme very suitable for subwavelength arbitrary patterns.

Effects of noise and parameter deviations in a bichromatic Raman white light cavity

We analyze the effects of noise and parameter deviations in a bichromatic Raman type white light cavity, with potential applications in precision measurements such as gravitational wave detection. The results show that the dispersion variation induced by parameter deviation can be controlled within 10. The laser phase noise decreases the dispersion magnitude while the amplitude noise increases it. Although we can always adjust the parameters to satisfy the white light condition, both noises make the cavity transmission curve uneven.

All optically controlled steering of light

We propose a scheme that provides all optically controlled steering of light beam. The system is based on steep dispersion of coherently driven medium. Using eikonal equation, we study the steering angle, the spread of optical beam, and the limits set by residual absorption of medium under conditions of electromagnetically induced transparency (EIT). Implementation of another scheme for ultra-short pulses is also discussed.

Entanglement Criteria for Continuous-Variable Systems

In 1935, Einstein, Podolsky, and Rosen (EPR) questioned the completeness of quantum theory in their seminal work [1]. The argument is based on two spatially separated systems, which are prepared into a bipartite wavefunction and then cease to interact with each other. According to quantum mechanics, a measurement on system I will reduce system II into certain wavefunction. A different measurement setting will reduce system II into another wavefunction. These two wavefunctions could be eigenfunctions of noncommuting operators. On the one hand, localism states that the choice of measurement in system I should not change system II. On the other hand, without disturbance, the eigenfunction of an operator provides the value of the physical quantity with certain, which corresponds to an element of physical reality. So by choosing different measurement settings, two noncommuting physical quantities could have simultaneous reality, which obviously contradicts with the uncertainty relation. Therefore, EPR argued that the wave function description in quantum theory cannot be complete.

Subwavelength interferometric lithography with classical lights : toward 2-dimensional patterns

We review our schemes of subwavelength interferometric lighthography based on classical lights, and show the procedures to obtain arbitrary subwavelength 2D patterns by multiple exposures. The first scheme is by correlating wave vector and frequency in a narrow band, multiphoton detection process. The second scheme is by preparing the system in a position dependent trapping state via phase shifted standing wave patterns.