Phonon Decoherence of Quantum Dots in Photonic Structures: Fundamental Limits to Photon Indistinguishability

There has been outstanding progress towards devising a deterministic interface between stationary and flying qubits with semiconductor quantum dots (QDs). Exploiting this interface at the ultimate quantum level requires a profound understanding and precise control of the sources of noise that decohere the QDs. Here we present the first unifying description of the interaction between QDs and phonons in photonic structures with a particular emphasis on the attainable indistinguishability of the emitted photons [1]. We show that the coherence depends critically on the geometric dimensionality of the structure for QDs embedded in a photonic sphere (0D), waveguide (1D), membrane (2D), or bulk medium (3D). In bulk, the dephasing rate scales drastically with temperature as T¹¹ and is negligible at low temperatures. In contrast, the stepwise phonon density of states of 1D structures leads to a linear temperature scaling and low photon indistinguishability even at sub-Kelvin temperatures.

[1] P. Tighineanu, C. L. Dreeßen, C. Flindt, P. Lodahl, and A. S. Sørensen, arxiv/1702.04812.