Periodic Reporting for period 1 - SMuPhoS (Solid-State Multi-Photon Sources for Larger-Scale Quantum Optics and Photonics)
Berichtszeitraum: 2017-12-01 bis 2019-11-30
We live in times where the laws of quantum physics are finding ways to make an impact in society, by enabling applications ranging from enhanced computing capabilities, to communication tasks where security is guaranteed by these laws of nature themselves. Quantum photonics exploits the non-classical (quantum) properties of light in order to develop light-based quantum technologies. In recent years, the advancement of quantum photonics had been hindered by the photon source technology exploited thus far, based on parametric conversion processes. This older photonic technology constrained the number of photons (single particles of light) that could be manipulated at once, hence limiting the complexity of the protocols being developed. As a result, advancements in quantum photonics have been slow and constrained to mostly non-scalable applications.
This project tackled some of these issues by utilising a different and recent technology: efficient single-photon sources based on semiconductor quantum dots. The objectives of this work consisted, in short, to advance upon the complexity of solid-state based quantum photonics by developing efficient and scalable multi-photon sources based on this quantum dot technology, allowing its use in scalable quantum photonics protocols. Two of such protocols are: on the one-hand, the demonstration of solid-state based heralded entanglement generation, and, on the other hand, the interference of an increasing number of single-photons in a scalable platform.
This project tackled some of these issues by utilising a different and recent technology: efficient single-photon sources based on semiconductor quantum dots. The objectives of this work consisted, in short, to advance upon the complexity of solid-state based quantum photonics by developing efficient and scalable multi-photon sources based on this quantum dot technology, allowing its use in scalable quantum photonics protocols. Two of such protocols are: on the one-hand, the demonstration of solid-state based heralded entanglement generation, and, on the other hand, the interference of an increasing number of single-photons in a scalable platform.
The work carried out during the project can be summarised in the following.
First, I developed and optimised techniques involving resonance fluorescence spectroscopy for single-photon generation and characterisation. From here, the user (final) efficiency of high-quality single-photon sources was increased to about 10%, denoting the direct detection of around 8 MHz of single-photon countrates from standard 80 MHz pump driving. This countrate number is among the highest recorded in the literature.
Subsequently, I designed and co-develop a system for active and efficient time-to-space mapping of the single-photon signal. This apparatus takes a stream of temporally-separated single-photons, all within the same spatial mode, and transforms it into various spatially-separated single-photons that propagate simultaneously. This constitutes the basis of a scalable multi-photon source.
The multi-photon source previously described has been used in a few different experiments. First, within the framework of a collaboration between France and Italy based groups, it served in the first demonstration of joint scalable photonic platforms: solid-state based multi-photon interference in reconfigurable and integrated photonic circuits. Secondly, in collaboration with an Australian research group, the source was also used for demonstrating the heralded generation of quantum entanglement, a version for creating entanglement that is required in scalable applications.
Later on, in collaboration with an Israel-based group, the high-rate single-photon source developed within this project was also utilised for demonstrating multi-partite entangled states known as cluster states, a resource highly sought-after in quantum computing applications.
Several of the results obtained during this project have been reported in written form, either submitted or already published in prestigious scientific journals.
First, I developed and optimised techniques involving resonance fluorescence spectroscopy for single-photon generation and characterisation. From here, the user (final) efficiency of high-quality single-photon sources was increased to about 10%, denoting the direct detection of around 8 MHz of single-photon countrates from standard 80 MHz pump driving. This countrate number is among the highest recorded in the literature.
Subsequently, I designed and co-develop a system for active and efficient time-to-space mapping of the single-photon signal. This apparatus takes a stream of temporally-separated single-photons, all within the same spatial mode, and transforms it into various spatially-separated single-photons that propagate simultaneously. This constitutes the basis of a scalable multi-photon source.
The multi-photon source previously described has been used in a few different experiments. First, within the framework of a collaboration between France and Italy based groups, it served in the first demonstration of joint scalable photonic platforms: solid-state based multi-photon interference in reconfigurable and integrated photonic circuits. Secondly, in collaboration with an Australian research group, the source was also used for demonstrating the heralded generation of quantum entanglement, a version for creating entanglement that is required in scalable applications.
Later on, in collaboration with an Israel-based group, the high-rate single-photon source developed within this project was also utilised for demonstrating multi-partite entangled states known as cluster states, a resource highly sought-after in quantum computing applications.
Several of the results obtained during this project have been reported in written form, either submitted or already published in prestigious scientific journals.
As an unexpected outcome of the project that goes beyond foreseen results: We discovered that novel and distinct states of quantum light can also be produced with the explored solid-state technology. We realised that the same devices, semiconductor quantum dots, used for two decades to generate single-photons can also be configured to emit quantum superpositions of photon-number Fock states, on demand. This means that now the field of quantum photonics can exploit a useful state of light that was very difficult to obtain in previous works, and this time we can generate them in an on-demand fashion. This result opens a series of possibilities for exploring novel quantum photonics protocols, such as so-called coherent-state quantum computation.