THESIS
2020
xiv, 121 pages : illustrations ; 30 cm
Abstract
Quantum entanglement attracts researchers for a long run as its fundamental role in quantum
physics and its potential application in the quantum information processing. Energy-time entangled photon pairs (biphotons) with sufficient narrow bandwidth have been widely explored in the
rapid-developing researches of quantum computation and quantum networks, due to their critical
significance to develop the photon-atom interaction based quantum interface.
In this Thesis, we present a comprehensive study of energy-time entanglement of photons with
narrow bandwidth. We first theoretically analyze four-level system and calculate the linear and
nonlinear atomic responses, and also adopt Heisenberg picture to describe the biphoton generation
and thoroughly investigate the biphoton temporal...[
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Quantum entanglement attracts researchers for a long run as its fundamental role in quantum
physics and its potential application in the quantum information processing. Energy-time entangled photon pairs (biphotons) with sufficient narrow bandwidth have been widely explored in the
rapid-developing researches of quantum computation and quantum networks, due to their critical
significance to develop the photon-atom interaction based quantum interface.
In this Thesis, we present a comprehensive study of energy-time entanglement of photons with
narrow bandwidth. We first theoretically analyze four-level system and calculate the linear and
nonlinear atomic responses, and also adopt Heisenberg picture to describe the biphoton generation
and thoroughly investigate the biphoton temporal and spectral properties.
After describing the two-dimensional
85Rb magneto-optical trap we work with, including magnetic field control and external-cavity diode laser systems, we demonstrate the generation of narrowband biphotons via backward four-wave mixing (FWM). These biphotons are naturally energy-time entangled because of energy conservation in the generation process. Therefore, we measure the two-photon temporal waveform and spectral correlation and confirm the Einstein-Podolsky-Rosen energy-time entanglement, which plays an essential role in quantum communication tasks
over long distances. To deeply characterize the temporal relative phase of our biphoton sources, we
propose and demonstrate a novel protocol of delta-quench measurement for directly measuring the quantum wave functions. This protocol is beyond traditional methods and requires simpler setup
and less resources.
We further realize and explore mirrorless optical parametric oscillation (OPO) by increasing
the parametric gain in the same backward FWM scheme. The system provides an ideal platform to
study OPO and squeezed light in the resonant atomic medium.
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