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Quantum Optical Control of Semiconductor Nanostructures
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Fig. 1 Quantum emitters being confined in a micro-cavity. The spatial distribution of cavity modes are directly imaged [Nano Letters 6, 2920 (2006)]. |
Semiconductor nanostructures such as quantum dots (QDs) have offered researchers unique opportunities to investigate sophisticated quantum optical effects in solid-state systems. These effects include quantum interference, Rabi oscillations, and photon antibunching, and were previously only observable in isolated atoms or ions. QDs can be readily integrated into optical microcavities, making them attractive for a number of applications, including particularly quantum information processing and high efficiency quantum light sources. One of the key issues in this area of research is the ability to coherently control solid-state quantum emitters. Successful implementation of coherent controls will open the way to new applications of quantum information science.
Our group has recently made significant progress in this endeavor. In particular, we have shown that resonantly controlled light emissions of quantum dots in a cavity can indeed be achieved. Shown in Fig. 2 is an example of resonant control of quantum emitters in the non-linear regime. In particular, when driven resonantly with the driving Rabi frequency exceeding subtantially the natural line width, the quantum emitter undergoes many Rabi cycles before emitting single photons. The quantum states involved become dressed states, resulting in well-defined side bands for the emitted spectrum (so-called Mollow triplets). This can be observed in the left panel, where the energy separation of the side bands is directly proportional to the driving field strength.
Also shown, in the right panel of Fig. 2, is the measured second order photon-photon correlation, g(2)(t), when the quantum emitters are coherently driven. In this case, g(2)(t) represents the probably of observing the second photon at time t after observing the first. Since the emission of the first photon initializes a quantum bit, g(2)(t) therefore presents the dynamic quantum information of the matter qubits (after initialization) being projected to the photons.
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