Abstract
The dark exciton state in semiconductor quantum dots (QDs) constitutes a long-lived solid-state qubit which has the potential to play an important role in implementations of solid-state-based quantum information architectures. In this work, we exploit deterministically fabricated QD microlenses which promise enhanced photon extraction, to optically prepare and read out the dark exciton spin and observe its coherent precession. The optical access to the dark exciton is provided via spin-blockaded metastable biexciton states acting as heralding states, which are identified by deploying polarization-sensitive spectroscopy as well as time-resolved photon cross-correlation experiments. Our experiments reveal a spin-precession period of the dark exciton of (0.82 ± 0.01) ns corresponding to a fine-structure splitting of (5.0 ± 0.7) μeV between its eigenstates ↑⇑±↓⇓. By exploiting microlenses deterministically fabricated above pre-selected QDs, our work demonstrates the possibility to scale up implementations of quantum information processing schemes using the QD-confined dark exciton spin qubit, such as the generation of photonic cluster states or the realization of a solid-state-based quantum memory.
Highlights
The quest for so-called quantum bits satisfying the stringent demands of future quantum computation and quantum communication scenarios is actively pursued world-wide.[1]
Solid-state-based matter qubits are of particular interest due to their capability for device integration,[2] which nowadays enables the development of sophisticated quantum-light sources.[3,4,5,6]
We employ deterministically fabricated microlenses above pre-selected QDs grown by metal-organic chemical vapor deposition (MOCVD) to optically prepare and read out the dark exciton (DE) spin qubit and observe its coherent precession
Summary
The quest for so-called quantum bits (qubits) satisfying the stringent demands of future quantum computation and quantum communication scenarios is actively pursued world-wide.[1]. Our experiments performed with deterministic photonic devices clearly reveal the coherent precession of the DE’s spin, which provides promises for scalable implementations of quantum information processing using the QD-confined DE as the solid-state-based spin qubit.
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