Energy-Tunable Sources of Entangled Photons: A Viable Concept for Solid-State-Based Quantum Relays

Abstract

We propose a new method of generating triggered entangled photon pairs with wavelength on demand. The method uses a microstructured semiconductor-piezoelectric device capable of dynamically reshaping the electronic properties of self-assembled quantum dots (QDs) via anisotropic strain engineering. Theoretical models based on k·p theory in combination with finite-element calculations show that the energy of the polarization-entangled photons emitted by QDs can be tuned in a range larger than 100 meV without affecting the degree of entanglement of the quantum source. These results pave the way towards the deterministic implementation of QD entanglement resources in all-electrically-controlled solid-state-based quantum relays.

Polarization-entangled twin photons from two-photon quantum-dot emission

“…However, in most high-quality semiconductor quantum-dot structures, the finestructure splitting between exciton levels limits the achievable degree of polarization entanglement [6]. Recent achievements show that this obstacle can be overcome by applying strain to the quantum dot [7][8][9] or by selecting those quantum dots on a given sample that possess a particularly small fine-structure splitting. As an alternative approach, it was shown theoretically that a high degree of polarization entanglement can also be obtained by using a direct two-photon emission process from the quantum-dot biexciton inside an optical cavityindependent of the fine-structure splitting [10].…”

Strain-inducedg-factor tuning in single InGaAs/GaAs quantum dots

“…As the strain-induced shift in the emission energy is at least a factor of 15 smaller than what has been reported in literature for similar devices [12,17], we expect that the observed effect can be greatly enhanced. Using novel devices an even larger tuning range will be possible [28][29][30]. By optimizing the size, shape, and composition of the dots, we can enhance the valence band contribution and improve even further.…”

Tuning of emission energy of single quantum dots using phase-change mask for resonant control of their interactions

“…One common challenge in QD engineering is to allow the optical transition in a QD to resonate with that of other QDs or with a cavity mode. Spectral tunability so that QDs emit indistinguishable photons is required in quantum repeaters and distributed quantum networks [1][2][3]. The tunability of mutual resonance of QDs can also be utilized in quantumtunneling-based [4] or energy-transfer-based devices [5], as well as in the manifestation and application of the superradiance mechanism [6][7][8][9].…”