Controlling Quantum Emitters through Spatially and Temporally Dependent Electric Fields

Beyond gradual improvement of current-day devices, nano and especially quantum technology promise to profoundly change data processing, communication, imaging and sensing. Delivering on this promise requires reliable control over the electronic state of individual nano-sized objects integrated within devices – a formidable task.A prime example of such nanoemitters are colloidal quantum dots (CQDs). The tunability of their properties, low production cost and ease of integration led to their increasing use in consumer electronics. However, in the discussion of future quantum technology, they are often overlooked. This is despite the recent introduction of a new type of CQDs: halide-perovskite nanocrystals (HPNCs) significantly outperforming more mature CQDs and demonstrating nearly coherent emission at low temperatures. Nevertheless, one obligatory capability for quantum protocols is still lacking in CQDs ¬– coherent control of its quantum state. ConQuEST proposes a clear path to fill this gap, demonstrating coherent control of the excited state of individual CQDs and its radiation. It relies on a key innovation: making use of the large quantum-confined Stark effect in CQDs through the application of time- and space-dependent electric-field waveforms to coherently manipulate the electrons’ wavefunction. The project establishes two novel experimental platforms to interact radio-frequency and terahertz waveforms with single CQDs. These implement ideas that go far beyond the state of the art, such as compressing single photons into femtosecond pulses and transforming a quantum dot into a local interferometric sensor. If successful, ConQuEST will revolutionize the manner in which quantum technology evolves, offering exciting new avenues especially for quantum sensing and imaging.