Abstract
We demonstrate the triggered emission of polarization-entangled photon pairs from the biexciton cascade of a single InAs quantum dot embedded in a GaAs/AlAs planar microcavity. Improvements in the sample design blue shifts the wetting layer to reduce the contribution of background light in the measurements. Results presented show that >70% of the detected photon pairs are entangled. The high fidelity of the state that we determine is sufficient to satisfy numerous tests for entanglement. The improved quality of entanglement represents a significant step towards the realization of a practical quantum dot source compatible with applications in quantum information.
Highlights
A source of entangled photon pairs is a vital commodity for quantum information applications based on quantum optics [1], such as entanglement based protocols for quantum key distribution [2], long distance quantum communication using quantum repeaters [3], and to realize an optical quantum computer [4]
(a) Typical quantum dot (b) Degenerate quantum dot photon pairs, so called because it can produce no more than two photons per excitation cycle [7]. Such a device could be a favourable alternative to parametric down converters for future applications in quantum optics, with the added benefit that it might be realized in a simple structure similar to an LED [8]
By controlling the polarization splitting using growth [12] or magnetic fields [13], we recently demonstrated for the first time that triggered entangled photon pairs are emitted by dots with zero polarization splitting [14]
Summary
A source of entangled photon pairs is a vital commodity for quantum information applications based on quantum optics [1], such as entanglement based protocols for quantum key distribution [2], long distance quantum communication using quantum repeaters [3], and to realize an optical quantum computer [4]. The emission of a pair of photons from a quantum dot is shown schematically, and begins with excitation of the biexciton state XX. The removal of the intermediate exciton level splitting is crucial in order to realize triggered entangled photon pair emission from a quantum dot, as shown in figure 1(b).
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