Abstract
AbstractSelf‐organized semiconductor quantum dots represent almost ideal two‐level systems, which have strong potential to applications in photonic quantum technologies. For instance, they can act as emitters in close‐to‐ideal quantum light sources. Coupled quantum dot systems with significantly increased functionality are potentially of even stronger interest since they can be used to host ultra‐stable singlet‐triplet spin qubits for efficient spin‐photon interfaces and for deterministic photonic 2D cluster‐state generation. An advanced quantum dot molecule (QDM) device is realized and excellent optical properties are demonstrated. The device includes electrically controllable QDMs based on stacked quantum dots in a pin‐diode structure. The QDMs are deterministically integrated into a photonic structure with a circular Bragg grating using in situ electron beam lithography. A photon extraction efficiency of up to (24 ± 4)% is measured in good agreement with numerical simulations. The coupling character of the QDMs is clearly demonstrated by bias voltage dependent spectroscopy that also controls the orbital couplings of the QDMs and their charge state in quantitative agreement with theory. The QDM devices show excellent single‐photon emission properties with a multi‐photon suppression of . These metrics make the developed QDM devices attractive building blocks for use in future photonic quantum networks using advanced nanophotonic hardware.
Highlights
In the field of photonic quantum technology, individual photons play a prominent role
We design, fabricate, and study quantum dot molecule (QDM) devices with intracavity contacts and a circular Bragg grating on top
The device design is optimized numerically to ensure a good balance between precise electrical field control of the QDM and high photon extraction efficiency
Summary
In the field of photonic quantum technology, individual photons play a prominent role. As flying qubits, they serve primarily as information carriers for low-loss quantum communication over long distances.[1,2,3,4,5,6] The information to be transmitted is typically encoded into the polarization of the photons.[7,8] In the case of quantum repeater networks, and for future distributed quantum computers and global quantum networks, it is of central importance to temporarily store and retrieve the quantum information to be transmitted for as long as possible in the form of stationary qubits in quantum memories.[9,10] In this context it is a great challenge to develop device concepts that simultaneously have a high level of performance in terms of singlephoton generation with high rate and high multiphoton suppression and that are suitable as efficient quantum memories. The NV-center in diamond, for example, has a very long spin coherence time, which makes it ideal as a quantum
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