Near-optimal single-photon sources in the solid state

Abstract

Single-photons are key elements of many future quantum technologies, be it for the realisation of large-scale quantum communication networks 1 for quantum simulation of chemical and physical processes 2 or for connecting quantum memories in a quantum computer 3 . Scaling quantum technologies will thus require efficient, on-demand, sources of highly indistinguishable single-photons 4 . Semiconductor quantum dots inserted in photonic structures are ultrabright single photon sources [5][6][7] , but the photon indistinguishability is limited by charge noise induced by nearby surfaces 8 . The current state of the art for indistinguishability are parametric down conversion single-photon sources, but they intrinsically generate multiphoton events and hence must be operated at very low brightness to maintain high single photon purity 9,10 . To date, no technology has proven to be capable of providing a source that simultaneously generates near-unity indistinguishability and pure single-photons with high brightness. Here, we report on such devices made of quantum dots in electrically controlled cavity structures. We demonstrate on-demand, bright and ultra-pure single photon generation. Application of an electrical bias on deterministically fabricated devices 11,12 is shown to fully cancel charge noise effects. Under resonant excitation, an indistinguishability of 0.9956±0.0045 is evidenced with a g (2) (0)=0.0028±0.0012. The photon extraction of 65% and measured brightness of 0.154±0.015 make this source 20 times brighter than any source of equal quality. This new generation of sources open the way to a new level of complexity and scalability in optical quantum manipulation.

Direct generation of linearly polarized single photons with a deterministic axis in quantum dots

“…To develop these non-classical light sources, the nanophotonics of semiconductor quantum dots (QDs) [7][8][9] has been a field under intense scientific investigation. Although ultrapure and highly indistinguishable single-photon generation has been achieved in various arsenide-based QD systems [10][11][12][13][14], the large band offsets and strong exciton binding energies of III-nitride materials are needed for the realization of polarized photon emission [15][16][17] and room temperature operation [18,19]. These polarized single-photon sources can then fulfill the need for on-chip polarization encoding in quantum cryptography, such as the BB84 protocol [20].…”

Classical boson sampling algorithms with superior performance to near-term experiments

“…The advent of integrated quantum photonics 10 has enabled large, complex, stable and programmable optical circuitry 11,12 , while recent advances in photon generation [13][14][15] and detection 16,17 have also been impressive. The possibility to generate many photons, evolve them under a large linear optical unitary transformation, then detect them, seems feasible, so the role of a boson sampling machine as a rudimentary but legitimate computing device is particularly appealing.…”

Two-Photon Interference from the Far-Field Emission of Chip-Integrated Cavity-Coupled Emitters

“…A number of works have reported such two-photon interference from a variety of solid-state quantum emitters such as defect centers, 10,11 dophants, 12 and quantum dots. [13][14][15][16][17][18][19][20][21][22] But these sources exhibit isotropic emission that is often difficult to collect efficiently.…”

“…27,28 The majority of the work to-date focused on a single emitter in a cavity, which can exhibit nearly perfect single photon purity and indistinguishability using resonant pumping techniques. [14][15][16][17] Two-photon interference has been demonstrated from two cavity-coupled emitters on different chips contained in separate cryostats. 21 But integrating multiple cavity-coupled emitters on the same chip remains extremely challenging due to spectral randomness of the emitters and errors in nanofabrication.…”

“…We could significantly reduce this effect by using resonant pumping [15][16][17] or quasi-resonant pumping 41,42 The temperature tuning method we employ also provides only a limited tuning range because the linewidth of the quantum dots broadens with increasing temperature, which will ultimately degrade the two-photon interference contrast. 14 Future devices could incorporate DC Stark shift 20 or local strain tuning 43 to enable wider tuning ranges.…”