High yield and ultrafast sources of electrically triggered entangled-photon pairs based on strain-tunable quantum dots

Abstract

Triggered sources of entangled photon pairs are key components in most quantum communication protocols. For practical quantum applications, electrical triggering would allow the realization of compact and deterministic sources of entangled photons. Entangled-light-emitting-diodes based on semiconductor quantum dots are among the most promising sources that can potentially address this task. However, entangled-light-emitting-diodes are plagued by a source of randomness, which results in a very low probability of finding quantum dots with sufficiently small fine structure splitting for entangled-photon generation (∼10−2). Here we introduce strain-tunable entangled-light-emitting-diodes that exploit piezoelectric-induced strains to tune quantum dots for entangled-photon generation. We demonstrate that up to 30% of the quantum dots in strain-tunable entangled-light-emitting-diodes emit polarization-entangled photons. An entanglement fidelity as high as 0.83 is achieved with fast temporal post selection. Driven at high speed, that is 400 MHz, strain-tunable entangled-light-emitting-diodes emerge as promising devices for high data-rate quantum applications.

Tuning exciton energy and fine-structure splitting in single InAs quantum dots by applying uniaxial stress

“…However, we found that a similar rotation of the exciton polarization angle under uniaxial stress observed in Ref. 25 was also observed when the FSS value decreases at first and then increases. We believe that the FSS can be reduced close to zero by exactly aligning the stress axis with the QD principle axes.…”

“…We believe that the FSS can be reduced close to zero by exactly aligning the stress axis with the QD principle axes. 25,26 In conclusion, we have experimentally demonstrated that the exciton and biexciton transition energies as well as FSS in single InAs QDs can be tuned in situ at low temperature cryostat by using a uniaxial stress device. The observed red shift of exciton emission energy and achieved minimum FSS value with increasing the tensile stress are up to 5 nm and down to 10 µeV, respectively.…”

“…By using a half-wave plate and a linear polarizer, polarization-resolved PL was measured to estimate the variation of FSS. With this experimental procedure, [25][26][27] we can determine the FSS with an accuracy of ∼µeV.…”

“…Recently, a new method of using a microstructured semiconductor-piezoelectric device to build scalable entangled photon sources with self-assembled QDs was proposed, 23,24 and was successfully demonstrated by combined uniaxial stresses along two orthogonal directions, i.e., along [110] and [1-10] crystal axis of GaAs. 25,26 In this letter, we report on a uniaxial stress device as shown in Fig. 1 which is developed to work at low temperature.…”

“…It was reported that there is about 33% QDs with a long axis parallel to the [110] orientation of the GaAs substrate and a perpendicular (2016) short axis along the [1-10] orientation. 25 The orientation of the QD sample which is attached to the latten plate is taken in such a way, that it makes the sample's [110] orientation as far as possible parallel to the direction of 0 • axis, then the 0 • axis of the sample holder can be very close to the long axis of the QD. In this case, the tensile stress further stretch QD shape, leading to an increase of FSS as observed when the stress is applied in the QD long axis direction (labeled as 0 • as depicted in Fig.…”