ABSTRACT
Entangled sources are important components for quantum information science and technology (QIST). The ability to generate high-quality entangled sources will determine the extent of progress in this field. Unlike previous schemes, a thin quasi-phase matching nonlinear crystal and a dense-wave-division-multiplexing device are used here to build high-quality versatile photonic sources with a simple configuration that can be used to perform Hong-Ou-Mandel interference, time-energy entanglement and multi-channel polarization entanglement experiments. The measurement results from various quantum optical experiments show the high quality of these photonic sources. These multi-functional photonic sources will be very useful in a variety of QIST applications.
ABSTRACT
Vector beams (VBs) are widely investigated for their special intensities and polarization distributions, which are useful in optical micromanipulation, optical microfabrication, optical communication, and single molecule imaging. To date, nonlinear frequency conversion (NFC) and manipulation of VBs remain challenging because of the polarization sensitivity of most nonlinear processes. Here we report an experimental realization of NFC and manipulation of VBs that can be used to expand the available frequency band. The main idea of our scheme is the introduction of a Sagnac loop to solve the polarization dependence problem of NFC in nonlinear crystals. Additionally, we find that a linearly polarized VB should be transformed into a hybrid-polarized VB in exponential form before performing NFC. The experimental results agree well with those of our theoretical model. The proposed method is also applicable to other wavebands and second-order nonlinear processes, and may be generalized to the quantum regime for single photons.
ABSTRACT
Silicon-on-chip photonic circuits are among some very promising platforms for generating nonclassical photonic quantum state, because of its low loss, small footprint, and compatibility with complementary metal-oxide-semiconductor (CMOS) and telecommunications techniques. Dense wavelength division multiplexing (DWDM) is a leading technique for enhancing the transmission capacity of both classical and quantum communications. To bridge the frequency gap between silicon-chip and other quantum systems, such as quantum memories, a quantum interface is indispensable. Here, we demonstrate a quantum interface for multiplexed energy-time entanglement states, which are generated on a silicon micro-ring cavity that is based on frequency up-conversion. By switching the pump wavelength, energy-time entanglement from any channel can be selected at will after being up-converted. The high visibilities of two-photon interference over three channels after frequency up-conversion clearly prove that the entanglement is fully preserved during the quantum frequency conversion (QFC) process. Our work provides new perspectives regarding channel capacity enhancement in quantum communications and for quantum resources being transferred between two different quantum systems.
ABSTRACT
The interferometer is one of the most important devices for revealing the nature of light and for precision optical metrology. Although many experiments were performed for probing photon behavior in various configurations, a complete study of photon behavior in a birefringent interferometer has not been performed, to our knowledge. By using an environmental turbulence immune Mach-Zehnder interferometer, we observe tunable photonic beatings by rotating a birefringent crystal versus the temperature of the crystal for both the single photon and two photons. Furthermore, the two-photon interference fringes beat 2 times faster than the single-photon interference fringes. This beating effect is used to determine the thermal dispersion coefficients of the two principal refractive axes with a single measurement: the two-photon interference shows superresolution and high sensitivity. Obvious differences between two-photon and single-photon interference are also revealed in unbalanced situations. In addition, the influence of the photon bandwidth on the beating behaviors that come from polarization-dependent decoherence is also investigated. Our findings will be important for better understanding the behavior of two-photon interference in a birefringent interferometer and for precision optical metrology with quantum enhancement.
