Mid-term milestone meeting“

At the end of April, we reached the halfway point of our project. The mid-term milestone meeting with the project sponsor took place on 10 April. We looked back on numerous development steps and looked ahead to what is still to come. Initially, we developed a project logo,

we have become visible on Instagram and our project website www.qoool-sensing.org has gone online. The first didactic content has been created in the form of a glossary.

Our project presented itself for the first time at the Maker Fair 2024 with a first plug-on module for the senseBox and made the first diamonds glow. QOOOL Kit Fluoro was created and officially launched at Quantum Effects 2024. We also made progress with QOOOL Kit Magneto. Our first setup for this, which we also presented to you at Quantum Effects 2024, still consists of a laser and our discrete microwave resonator and delivered the first ODMR signals. After the trade fair, ‘The Lämp’ was created in a limited edition, a battery-powered pocket quantum demonstrator that also demonstrates fluorescence of the NV in the diamond. In the meantime, we have successfully tested light sources and colour filters that have led to smaller setups, which also provide ODMR signals and on which we have tested different diamonds.

We have made a microcontroller platform fit to control a microwave generator, read in the fluorescence signals of the diamond and display the fluorescence live via the microwave frequency in GNU Octave. This is how we were able to make the first ODMR recordings without the use of an oscilloscope, without

and with a magnet near the setup.

For precise manipulation of spin states, a microwave field of defined frequency must be applied efficiently to the NV centre. For this purpose, a high-frequency resonator was developed with the aim of maximising the amplitude of the oscillating magnetic field.

Mesh view of resonator in electromagnetic simulation

To this end, a complete design chain for the resonator was established and continuously developed - starting with impedance-adapted circuit development and simulation, through physical modelling and electromagnetic simulation, to production using high-precision RF processing techniques such as laser cutting. This is followed by frequency-based characterisation and experimental tests. The resonator has now been optimised in several versions and has already demonstrated reliable performance in ODMR experiments. Nevertheless, development is continuing with the aim of achieving a broad bandwidth, high energy efficiency and a miniaturised and flexible design.

While we are still working on a good solution for the microwave resonator and the final microwave generator is being developed, the basis has already been created for porting everything else to the senseBox. To this end, simulations are currently underway and various setups are being trialled, which should make it possible to produce resonators with processes suitable for series production. Resonators have already been produced on Rogers, PEEK and PI.

There is also a first preview of QOOOL Kit Magneto. For this purpose, we have developed the π-Mk1 platform, which will form the basis for our QOOOL Kit Magneto.It contains all the critical components of the NV magnetometer, housed in a space of π cm³, and will provide the senseBox with the fluorescence signals in a form that it can handle.

At the same time, we are currently working flat out on the web simulator that will allow QOOOL Kit Fluoro and later QOOOL Kit Magneto to be tested virtually. The simulator will soon be online on our project page and we are very proud of it.

In order to be able to use the two QOOOL Kits Fluoro and Magneto in schools and extracurricular learning centres later on, didactic concepts have been and are being developed and tested in parallel to create a meaningful transition from the learning content taught at school to the new content of quantum technology. For example, an experiment on colour centres with salts in glass ampoules and a Tesla coil was developed. Here, colour centres can be generated in a targeted manner using school resources and a convincing comparison of theory (previously covered in school) and experiment can be carried out.The activities of QOOOL Sensing have already found their way into teacher training programmes.

The second half of the project remains exciting and we are already looking forward to presenting QOOOL Kit Magneto to you virtually and in reality. Stay tuned for what awaits you.