Quantum coherence in quantum dot systems

Chi‐Wai Chow, S. Michael, Hans Christian Schneider

A many-body theory for quantum coherence in a semiconductor quantum-dot system is presented. We present the theory in detail for a Λ scheme in a InGaAs–GaAs quantum dot with a pulsed drive field. The paper shows the significant differences in the predictions of this theory and those of an independent-particle treatment, adapted from atomic quantum coherence theory. Specifically, the influence of the quantum-dot level structure on group-velocity slowdown is discussed, and the influence of different Coulomb renormalization effects is analysed.

S. Abdel‐Khalek, K. Berrada, A. Alkaoud

Jian Qi Shen, Rui Xi Zeng

Quantum-dot-molecular phase coherence (and the relevant quantum-interference-switchable optical response) can be utilized to control electromagnetic wave propagation via a gate voltage, since quantum-dot molecules can exhibit an effect of quantum coherence (phase coherence) when quantum-dot-molecular discrete multilevel transitions are driven by an electromagnetic wave. Interdot tunneling of carriers (electrons and holes) controlled by the gate voltage can lead to destructive quantum interference in a quantum-dot molecule that is coupled to an incident electromagnetic wave, and gives rise to a quantum coherence effect (e.g., electromagnetically induced transparency, EIT) in a quantum-dot-molecule dielectric film. The tunable on- and off-resonance tunneling effect of an incident electromagnetic wave (probe field) through such a quantum-coherent quantum-dot-molecule dielectric film is investigated. It is found that a high gate voltage can lead to the EIT phenomenon of the quantum-dot-molecular systems. Under the condition of on-resonance light tunneling through the present quantum-dot-molecule dielectric film, the probe field should propagate without loss if the probe frequency detuning is zero. Such an effect caused by both EIT and resonant tunneling, which is sensitive to the gate voltage, can be utilized for designing devices such as photonic switching, transistors, and logic gates.

Eduardo Vaz, Jordan Kyriakidis

Rares Andrei Barcan, I. Samaras, K. G. Barr +3 more

Deterministically positioned pyramidal InGaAs quantum dots (QDs) exhibit exceptional quantum properties, making them highly promising candidates for scalable on-chip quantum information processing. In this work, we investigate the coherent dynamics of positively charged excitons under the influence of strong magnetic fields in the Faraday configuration. Pyramidal quantum dots exhibit a fourfold splitting of the charged excitons even in the Faraday configuration, giving rise to an optically addressable double-Lambda ([Formula: see text]) system akin to self-assembled quantum dots in oblique magnetic fields. Here, we investigate ultrafast complete coherent control of the trion to ground state transition utilizing advanced optical resonant excitation techniques and we observe quantum coherence over timescales that are similar to other prominent quantum dot platforms. These results pave the way towards establishing site-controlled pyramidal InGaAs QDs as scalable platforms for quantum information processing, expanding the reach of coherent control to new quantum systems.