German Researchers Develop Compact, Cost-Effective LED Quantum Sensor for Broad Applications

Researchers from Münster University of Applied Sciences have developed a compact, fully integrated LED quantum sensor, one of the smallest of its kind. The sensor, which is based on nitrogen vacancy (NV) centers in diamond microcrystals, integrates a pump light source, photodiode, microwave antenna, filtering, and fluorescence detection. It offers an all-electric interface and has a sensitivity of 2832 nT/Hz. The sensor can be easily produced using generally available parts and consumes around 0.1 W of power, making it suitable for a wide range of stationary and handheld systems. This development could lead to wider usage of quantum magnetometers in non-laboratory environments.

What is the New Compact and Fully Integrated LED Quantum Sensor?

A team of researchers from the Department of Electrical Engineering and Computer Science and the Department of Engineering Physics at Münster University of Applied Sciences in Germany have developed a compact and fully integrated LED quantum sensor. The sensor is based on nitrogen vacancy (NV) centers in diamond microcrystals. The team includes Jens Pogorzelski, Ludwig Horsthemke, Jonas Homrighausen, Dennis Stiegekötter, Markus Gregor, and Peter Glösekötter.

The sensor is one of the smallest fully integrated quantum sensors to date. It is an extremely cost-effective device that integrates a pump light source, photodiode, microwave antenna, filtering, and fluorescence detection. The sensor offers an all-electric interface without the need to adjust or connect optical components. It has a sensitivity of 2832 nT/Hz and a theoretical shot noise limited sensitivity of 287 nT/Hz.

The sensor can be easily produced in a small series since only generally available parts were used. The form factor of 6.9 * 39 * 159 mm3 combined with the integration level is the smallest fully integrated NV-based sensor proposed so far. With a power consumption of around 0.1 W, this sensor becomes interesting for a wide range of stationary and handheld systems. This development paves the way for the wide usage of quantum magnetometers in non-laboratory environments and technical applications.

How Does the Quantum Sensor Work?

Quantum magnetometry based on optically detected magnetic resonance (ODMR) of nitrogen vacancy centers in diamond nano or microcrystals is a promising technology for sensitive integrated magnetic field sensors. Currently, this technology is still cost-intensive and mainly found in research.

The NV center is a point defect in diamond. The diamond crystal structure is shown in Figure 1a. Two of the carbon atoms are replaced by a nitrogen atom and an adjacent vacancy. For an ensemble of NV centers in a solid diamond, all four orientations within the tetrahedral structure of the diamond are possible.

A negatively charged NV center is a spin S=1 system with spin triplets in the ground state (ground state 3A2) and in the excited state (3E). The optical excitation of the ground state is spin-conserving. The decay of electrons in the ms=0 spin state leads to fluorescence with a dominant wavelength of 637nm, while the ms=1 state has a higher probability of non-radiative transitions to the 1A1 singlet state.

What are the Applications of the Quantum Sensor?

In recent years, negatively charged NV centers in diamond have become established in the field of quantum-based sensing. NV centers can be used to build highly sensitive magnetic field sensors, even in the fT/Hz range. These can be kept extremely small with spatial resolutions down to atomic size. This sensor technology can also measure magnetic fields very accurately combined with low energy and space requirements.

NV centers can also be used to measure temperatures, electric fields, and there are also applications in the field of quantum computing. Other magnetic sensing protocols using the NV center include an all-optical approach using spin mixing in the NV ground state or measurement of the infrared absorption of the infrared transition with near shot-noise limited sensitivity. As they are a solid-state system in diamond, the sensors can be operated at room temperature. Therefore, the structure can be kept less complex as cryogenic temperatures are not required.

The magnetic sensing capability of the NV center is given by the interaction of an external magnetic field (Bz, green arrow) with the electron spin. Due to the Zeeman effect, the ms=1 electron spin states are shifted by the projected parallel component B (blue arrow). This shift can be read out in optically detected magnetic resonance (ODMR) measurements. Without any applied magnetic field, a zero-field splitting (ZFS) is still visible due to internal crystal strain. The ZFS center frequency D=2.87 GHz at room temperature shifts with temperature and is used for temperature sensing.

What is the Future of Quantum Sensors?

The development of this compact and fully integrated LED quantum sensor is a significant step forward in the field of quantum-based sensing. The sensor’s small size, low power consumption, and cost-effectiveness make it an attractive option for a wide range of stationary and handheld systems.

The sensor’s ability to measure magnetic fields, temperatures, and electric fields with high sensitivity and accuracy opens up a wide range of potential applications. These include quantum computing, where the sensor’s ability to operate at room temperature could simplify system design and reduce costs.

The use of generally available parts in the sensor’s construction also means that it can be easily produced in small series. This could pave the way for the wider use of quantum magnetometers in non-laboratory environments and technical applications, bringing the benefits of quantum-based sensing to a broader audience.

Conclusion

The compact and fully integrated LED quantum sensor developed by the team at Münster University of Applied Sciences represents a significant advancement in the field of quantum-based sensing. The sensor’s small size, low power consumption, and cost-effectiveness, combined with its high sensitivity and accuracy, make it an attractive option for a wide range of applications. The use of generally available parts in the sensor’s construction also means that it can be easily produced in small series, potentially paving the way for the wider use of quantum magnetometers in non-laboratory environments and technical applications.