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The integration of entangled photon emitters in nanophotonic structures designed for the broadband enhancement of photon extraction is a major challenge for quantum information technologies. We study the potential of quantum dot (QD) microlenses to act as efficient emitters of maximally entangled photons. For this purpose, we perform quantum tomography measurements on InGaAs QDs integrated deterministically into microlenses. Even though the studied QDs show non-zero excitonic fine-structure splitting (FSS), polarization entanglement can be prepared with a fidelity close to unity. The quality of the measured entanglement is only dependent on the temporal resolution of the used single-photon detectors compared to the period of the excitonic phase precession imposed by the FSS. Interestingly, entanglement is kept along the full excitonic wave-packet and is not affected by decoherence. Furthermore, coherent control of the upper biexcitonic state is demonstrated.
Spin qubits involving individual spins in single quantum dots or coupled spins in double quantum dots have emerged as potential building blocks for quantum information processing applications. It has been suggested that triple quantum dots may provid
We present theory and calculations for coherent high-fidelity quantum control of many-particle states in semiconductor quantum wells. We show that coupling a two-electron double quantum dot to a terahertz optical source enables targeted excitations t
We investigate coherent time-evolution of charge states (pseudo-spin qubit) in a semiconductor double quantum dot. This fully-tunable qubit is manipulated with a high-speed voltage pulse that controls the energy and decoherence of the system. Coheren
Multi-electron semiconductor quantum dots have found wide application in qubits, where they enable readout and enhance polarizability. However, coherent control in such dots has typically been restricted to only the lowest two levels, and such contro
A semiconductor quintuple quantum dot with two charge sensors and an additional contact to the center dot from an electron reservoir is fabricated to demonstrate the concept of scalable architecture. This design enables formation of the five dots as