arXiv subjects

Timo Kaldewey

Publications and source records attributed to Timo Kaldewey.

3 recordsLinked to original sources

arXiv2017

Coherent and robust high-fidelity generation of a biexciton in a quantum dot by rapid adiabatic passage

A biexciton in a semiconductor quantum dot is a source of polarization-entangled photons with high potential for implementation in scalable systems. Several approaches for non-resonant, resonant and quasi-resonant biexciton preparation exist, but all have their own disadvantages, for instance low fidelity, timing jitter, incoherence or sensitivity to experimental parameters. We demonstrate a coherent and robust technique to generate a biexciton in an InGaAs quantum dot with a fidelity close to one. The main concept is the application of rapid adiabatic passage to the ground state-exciton-biexciton system. We reinforce our experimental results with simulations which include a microscopic coupling to phonons.

cond-mat.mes-hall↗

arXiv2017

Demonstrating the decoupling regime of the electron-phonon interaction in a quantum dot using chirped optical excitation

Excitation of a semiconductor quantum dot with a chirped laser pulse allows excitons to be created by rapid adiabatic passage. In quantum dots this process can be greatly hindered by the coupling to phonons. Here we add a high chirp rate to ultra-short laser pulses and use these pulses to excite a single quantum dot. We demonstrate that we enter a regime where the exciton-phonon coupling is effective for small pulse areas, while for higher pulse areas a decoupling of the exciton from the phonons occurs. We thus discover a reappearance of rapid adiabatic passage, in analogy to the predicted reappearance of Rabi rotations at high pulse areas. The measured results are in good agreement with theoretical calculations.

cond-mat.mes-hall↗

arXiv2017

Optical nanoscopy via quantum control

We present a scheme for nanoscopic imaging of a quantum mechanical two-level system using an optical probe in the far-field. Existing super-resolution schemes require more than two-levels and depend on an incoherent response to the lasers. Here, quantum control of the two states proceeds via rapid adiabatic passage. We implement this scheme on an array of semiconductor self-assembled quantum dots. Each quantum dot results in a bright spot in the image with extents down to 30 nm (λ/31). Rapid adiabatic passage is established as a versatile tool in the super-resolution toolbox.

cond-mat.mes-hall↗