Periodic Reporting for period 1 - QUDOT-TECH (Quantum Dots for Photonic Quantum Information Technologies)
Berichtszeitraum: 2020-01-01 bis 2021-12-31
We are presently at the verge of a second revolution of quantum science, where quantum engineering based on direct exploitation of fundamental quantum mechanical abilities such as superposition and entanglement promise entire new technologies for society. In QUDOT-TECH, we build from the semiconductor quantum dot - the most mature optical quantum information technology - and propose to construct a scalable platform for optical quantum information processing. Our novel platform will pave the way for quantum technology to become a reality with benefits for society within health care, drug design, quantum chemistry, logistic optimization etc.
The main goal of the network is to produce the next generation of ESRs, who are trained to work across disciplinary and sectorial boundaries and therefore bring about step-changes in both research and technology development relating to optical quantum information processing.
The QUDOT-TECH network will train the ESRs to be capable of working at all technological maturity levels, from the basic research level to the mature application level with opportunities for industrial exploitation and commercialization. The network is organized in three scientific workpackages, reflecting technological maturity levels from highly mature technologies (work package 1) adopted by spinout companies, to more applied research (work package 2) and to exploratory basic research (work package 3). Complemented by education in entrepreneurship and innovation, the team of ESRs will contribute to moving Europe into a leading position in scientific and technological innovation within optical quantum technologies.
The main goal of the network is to produce the next generation of ESRs, who are trained to work across disciplinary and sectorial boundaries and therefore bring about step-changes in both research and technology development relating to optical quantum information processing.
The QUDOT-TECH network will train the ESRs to be capable of working at all technological maturity levels, from the basic research level to the mature application level with opportunities for industrial exploitation and commercialization. The network is organized in three scientific workpackages, reflecting technological maturity levels from highly mature technologies (work package 1) adopted by spinout companies, to more applied research (work package 2) and to exploratory basic research (work package 3). Complemented by education in entrepreneurship and innovation, the team of ESRs will contribute to moving Europe into a leading position in scientific and technological innovation within optical quantum technologies.
A main QUDOT-TECH activity is to train the ESRs scientifically, in communication and dissemination, in exploitation and entrepreneurship. Scientific training has taken place in the form of local training, first secondments and short visits, as well as in the form of Advanced Scientific Courses during the two of the total of three planned summer schools. Transferable skills training has taken place predominantly during the Transferable Skills Modules at the two summer schools.
Highlights of the scientific work carried out in the first project period are briefly reported below:
Sources with vertical emission: Tunability of the nano-trumpet SPS geometry has been implemented at CEA combined with broadband Purcell enhancement. New designs allowing for improved collection from connected pillar structures have been fabricated at C2N, and four-photon measurements have been performed in collaboration with SAP. Furthermore, significant progress in SPS fiber-pig-tailing and integration in closed-cycle cryostat has been achieved at QUA.
On-chip integration: A numerical simulation framework for analyzing and optimizing on-chip ridge waveguide single-photon source designs based on a FEM model has been constructed at DTU in collaboration with JCM. Similarly, a model for analyzing V groove waveguide designs based on a FDTD model has been established at DTU. Wafer-bonding technology has been developed at DTU allowing for integration of quantum dots in a high-index GaAs/SiO2 platform. The superconducting properties of MoSi deposited on GaAs wafers for integration of on-chip detectors have been investigated at BAS, and the results are well understood.
Spin-photon interfaces: A analytical and numerical framework based on a dedicated input-output formalism has been established at NEEL. The framework takes into account solid-state-induced decoherence, finite cooperativity and imperfect photon detection. New samples for use in spin-photon interface experiments have been fabricated by C2N, where quantum non-demolition measurements have also been realized between a single spin and coherent pulses of polarized light. Good progress in the control of the decoherence induced by the nuclear spin environment has been achieved by CAM.
Phononic engineering: Phononic bandgaps at GHz frequencies resulting from phononic shield elements have been numerically investigated at BAS. The resonators and acoustic shield elements have been fabricated at NBI, and high quality factors have been measured. Additionally, numerical simulations were carried out in order to assess the vibration modes of oscillating nanowires with different geometries at DTU. Furthermore, nanowire-quantum dot geometries fulfilling all requirements for performing quantum non-demolition measurements were identified.
Highlights of the scientific work carried out in the first project period are briefly reported below:
Sources with vertical emission: Tunability of the nano-trumpet SPS geometry has been implemented at CEA combined with broadband Purcell enhancement. New designs allowing for improved collection from connected pillar structures have been fabricated at C2N, and four-photon measurements have been performed in collaboration with SAP. Furthermore, significant progress in SPS fiber-pig-tailing and integration in closed-cycle cryostat has been achieved at QUA.
On-chip integration: A numerical simulation framework for analyzing and optimizing on-chip ridge waveguide single-photon source designs based on a FEM model has been constructed at DTU in collaboration with JCM. Similarly, a model for analyzing V groove waveguide designs based on a FDTD model has been established at DTU. Wafer-bonding technology has been developed at DTU allowing for integration of quantum dots in a high-index GaAs/SiO2 platform. The superconducting properties of MoSi deposited on GaAs wafers for integration of on-chip detectors have been investigated at BAS, and the results are well understood.
Spin-photon interfaces: A analytical and numerical framework based on a dedicated input-output formalism has been established at NEEL. The framework takes into account solid-state-induced decoherence, finite cooperativity and imperfect photon detection. New samples for use in spin-photon interface experiments have been fabricated by C2N, where quantum non-demolition measurements have also been realized between a single spin and coherent pulses of polarized light. Good progress in the control of the decoherence induced by the nuclear spin environment has been achieved by CAM.
Phononic engineering: Phononic bandgaps at GHz frequencies resulting from phononic shield elements have been numerically investigated at BAS. The resonators and acoustic shield elements have been fabricated at NBI, and high quality factors have been measured. Additionally, numerical simulations were carried out in order to assess the vibration modes of oscillating nanowires with different geometries at DTU. Furthermore, nanowire-quantum dot geometries fulfilling all requirements for performing quantum non-demolition measurements were identified.
In spite of the numerous delays in project activities due to the corona pandemic, the project output in the first period includes: A nanopost SPS geometry with a measured extraction efficiency of 0.35 and a broadband Purcell enhancement of 5 has been demonstrated in a joint effort led by CEA. A study on molecular beam epitaxy grown quantum dots with a contaminated aluminum evaporation cell was conducted by RUB and a way of addressing this problem to restore growth of excellent low noise heterostructures was identified. Optical driving of the radiative Auger transition in a trion of a semiconductor quantum dot was demonstrated linking few-body Coulomb interactions and quantum optics. On driving both the radiative Auger and the fundamental transition simultaneously, a reduction of the fluorescence signal by up to 70% was observed.
In the second project period, the projects aims at continuously producing and communicating progress results within optical quantum-dot based quantum technology, both to the scientific community and the wider audience. In particular, we expect to achieve our project objectives of demonstrating the scalability of optical quantum information technology, through the demonstrations of unprecedented SPS and entangled-photon pair brightness, on-chip integration capability and optical gating with full control of the decoherence. While the scientific work performed so far remains of a fundamental research character and has been severely impacted by the corona crisis, selected work has already been presented at international conferences including Quantum Information and Measurement VI 2021, CLEO 2021 and the APS March Meeting 2021.
In the second project period, the projects aims at continuously producing and communicating progress results within optical quantum-dot based quantum technology, both to the scientific community and the wider audience. In particular, we expect to achieve our project objectives of demonstrating the scalability of optical quantum information technology, through the demonstrations of unprecedented SPS and entangled-photon pair brightness, on-chip integration capability and optical gating with full control of the decoherence. While the scientific work performed so far remains of a fundamental research character and has been severely impacted by the corona crisis, selected work has already been presented at international conferences including Quantum Information and Measurement VI 2021, CLEO 2021 and the APS March Meeting 2021.