The seed laser system is responsible for exciting the fluorescent defect in the hexagonal boron nitride (hBN) crystal lattice. While developing a space proofed laser is expensive and cumbersome, we take the new space approach where we test different promising laser systems under space conditions and select a suitable laser that can operate in space. This not only includes the laser itself, but also the control electronics required to operate the laser. At a later stage, we want to be able to modulate the laser intensity for on-demand excitation of the quantum emitter.
The integrated quantum light source is the heart of the quantum payload. The transition wavelength of the hBN emitter must be compatible with the laser system: the laser needs a higher photon energy than the energy difference between ground and excited state. But the laser must still fall into the absorption band of the emitter for an efficient excitation. The quantum emitter shall be directly interfaced with the quantum interferometer in WP 3 to reduce the footprint of the integrated quantum light source.
The quantum interferometer is based on a laser-written waveguide in glass which allows us to write arbitrary waveguiding structures, including our multipath interferometer with which we can probe extended quantum theories in microgravity. With the waveguide we can also implement direction couplers (eg 50:50 beam splitters) to measure the second-order correlation function of our photon source and thereby verify that the photon source emits true single photons.
When the emitter is coupled to high-Q resonators, we can funnel the emission into the resonant wavelength and thereby strongly enhance the spectral brightness of the photon source. This provides a promising route for locking the emitter to narrowband atomic transitions of alkali-metal vapors in gas cells. The interaction between the single photons and the vapor can provide a feedback signal for the locking loop. With a better understanding of this interaction, we want to develop a direct interface to quantum memories that do not require frequency conversion between the photon source and the quantum memory.
Once all individual sub-systems have been developed and qualified, all components need to be integrated together to form the quantum payload. The optical interface between components (seed laser, integrated quantum light source, and commercial single photon detectors) is realized by optical single-mode fibers.
The interfaces between the commercial 3U CubeSat and the quantum payload, their intrinsic interfaces, as well as with the payload controller are designed in WP 6. This includes thermal, mechanical, and electronical aspects.
All individual components, as well as the final flight module need to be qualified for use in space environments. Our verification experiments include mechanical shock and vibration tests, irradiation with gamma-rays, as well as thermal-vacuum cycling.
After the satellite launch in 2024, the satellite needs to be operated and controlled from the ground. This includes adjusting experimental parameters as well as the download of the experimental data.
There is also a dedicated work package concerned with the management of the entire project as well as ensuring the scientific communication between the partners, associated partners, contractors, as well as the scientific community.
