Abstract
Single photons and entangled photon pairs are a key resource of many quantum secure communication and quantum computation protocols, and non-Poissonian sources emitting in the low-loss wavelength region around 1,550 nm are essential for the development of fibre-based quantum network infrastructure. However, reaching this wavelength window has been challenging for semiconductor-based quantum light sources. Here we show that quantum dot devices based on indium phosphide are capable of electrically injected single photon emission in this wavelength region. Using the biexciton cascade mechanism, they also produce entangled photons with a fidelity of 87 ± 4%, sufficient for the application of one-way error correction protocols. The material system further allows for entangled photon generation up to an operating temperature of 93 K. Our quantum photon source can be directly integrated with existing long distance quantum communication and cryptography systems, and provides a promising material platform for developing future quantum network hardware.
Highlights
Single photons and entangled photon pairs are a key resource of many quantum secure communication and quantum computation protocols, and non-Poissonian sources emitting in the low-loss wavelength region around 1,550 nm are essential for the development of fibrebased quantum network infrastructure
Single photon emission has been demonstrated under optical excitation from InAs/InP dots grown by molecular beam epitaxy in the well-explored Stranski–Krastanow mode[16,17,18,19,20,21,22], the resulting structures are often asymmetric dashes or horns, preventing access to the low intrinsic energy splitting of the photon polarisation states[23] needed for entangled photon generation
The key features of our device are described in the cartoon in Fig. 1a, with a detailed fabrication description given in Methods
Summary
Single photons and entangled photon pairs are a key resource of many quantum secure communication and quantum computation protocols, and non-Poissonian sources emitting in the low-loss wavelength region around 1,550 nm are essential for the development of fibrebased quantum network infrastructure. Quantum dots (QDs), semiconductor islands capable of confining charges in a discrete energy level structure, are well-explored in the contexts of quantum communication and computing Their implementation in InAs/GaAs, emitting around 900 nm, has provided a rich physical system to demonstrate basic building blocks of a quantum network, such as individual entangled photon pairs from electrically driven devices[5], photon sorters[6,7] and even entanglement between distant spins[10,11]. It has been shown that QD growth using metalorganic vapour phase epitaxy (MOVPE), which is the industry favoured growth method, can create droplet QDs with low fine structure splitting (FSS)[24] We extend this growth scheme to produce the first optoelectronic devices for single and entangled photon emission in the 1,550 nm telecom window. We extend the working temperature up to 93 K, allowing operation with liquid nitrogen or closed-cycle coolers
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