How does a highly complex physical laboratory setup become a marketable product? The secret lies in reduction, says Dr Robert Staacke, whose startup focuses on optical quantum sensors: Strip things down until only the essentials remain, and use minimal functions that will fit inside a practical housing—instead of overloaded optical tables—and can be understood without having studied physics. Industrial magnetometers from Quantum Technologies are set to revolutionise automotive sensor technology and beyond. They are supported by the distributor reichelt elektronik, who was convinced of the technology at an early stage and entered into a partnership with the company.
Measuring tasks continue to pose new challenges in factory and process automation as well as in automotive and medical technology. Precise, reproducible and scalable processes are required that allow for advantageous integration into applications under adverse conditions — at high or low temperatures, in electromagnetic fields or with limited installation space. In the field of magnetometry, or magnetic field measurement, the focus has been on quantum sensors for several years, which achieve an extraordinary sensitivity and accuracy compared to conventional measuring sensors. Unlike Hall-effect or magnetoresistive sensors, for example, they react robustly to temperature fluctuations and provide hysteresis-free measurement. This is based on quantum physical interactions on a subatomic scale, which can be generated and controlled in diamond crystals, for example.
With diamonds and laser for magnetic field measurement
Quantum Technologies, a spin-off of the University of Leipzig, has been developing quantum magnetometers since 2020. Target applications include highly sensitive angle encoders, robust sensor technology for current sensors and electric motor monitoring. “Each and every one is a problematic area of application,” says Dr Robert Staacke, co-founder and CEO of Quantum Technologies, “including for quantum sensors. Either the necessary cooling is a disadvantage when integrating the measurement procedures, or microwave radiation is required. But this can generate heat, and it is often difficult to galvanically separate the sensor and the measuring environment.” These are the obstacles Staacke and his team want to overcome with their work.
As a doctoral student in Leipzig, Staacke had already conducted research on magnetic field sensors that use quantum effects. Typically, scientists focus on so-called colour centres, in particular nitrogen-vacancy centres (NV), in diamond crystals. They are suitable for measuring magnetic fields and their changes optically. NV centres are created by replacing one of the carbon atoms in the diamond crystal lattice, a modification of the element carbon, with nitrogen, where an adjacent carbon atom is missing. This defect pair of nitrogen atom (N) and lattice vacancy (vacancy = V) is characterised by having a spin of one. External magnetic fields influence the energy levels of the spin states of the centre, which in turn results in an observable change in fluorescence. Using light, the NV centre can be energised. When the resulting fluorescence is monitored, conclusions can be drawn about the strength of the relevant magnetic field.
Microwaves eradicated from the sensor
In contrast to SQUIDs (Superconducting Quantum Interference Devices), NV magnetometers can detect further measuring ranges and operate up to room temperature and beyond. However, it is typically necessary to orient the NV centres spatially in accordance with the magnetic field and to use microwave radiation. Although NV sensors do not require the complex cooling equipment required for SQUIDs, microwaves also require special setups — for example, antennas in close proximity to the diamond or shielding enclosures to increase the sensitivity of the measurement. The innovative technology of Quantum Technologies therefore pursues an approach that works independently of the direction of the magnetic field and without microwave radiation. Instead of an extended and homogeneous diamond crystal, diamond nanoparticles are used on the tip of an optical fibre. The statistically distributed alignment of the particles eliminates the direction dependence, or anisotropy, of material properties, which is inevitable in crystals. The magnetic field measurement is now isotropic.
This technology has two key advantages. On the one hand, the sensors work purely optically. They can be easily supplied where they are required on the tip of an optical fibre, without any electrically conductive or magnetic material. The measurement can therefore be electrically isolated and is unaffected by electromagnetic interference sources. On the other hand, the measuring setup is compact, simple and can also be integrated into difficult-to-access applications such as electric motors.
That was not always the case. The typical image of a laboratory in which research is conducted at NV centres is that of complicated testing equipment setups and huge optical tables strewn with components and devices. Staacke says, “This is why we had our doubts at the start. How could a product ever come out of that?” His team’s approach was somewhat atypical for science, which is usually about measuring even more precisely with even more complexity in order to reveal an additional physical effect. “The main question we asked ourselves was: how can we reduce complexity and simplify the system? What can we forgo so that our product still has an advantage that the current state of the art does not offer?”
The minimalist quantum sensor
Staacke describes the minimum equipment required as follows: “We need diamond nanoparticles, a light source and a detector. We then evaluate the red fluorescence, and we don’t really need anything more. This is not the most sensitive sensor that can be realised with NV centres, but we do gain galvanic isolation. The diamond nanoparticles give us an isotropic measurement option and a tiny measuring point, which opens up entirely new application possibilities.”
The directional and interference-free measurement as well as the sensor’s small footprint are vital to the applications that Quantum Technologies wants to tap into — directly in the air gap of an electric motor, for example, or within an electric vehicle battery, in high-voltage power plants, in invasive medical technology and radiology or in non-destructive inline material tests for the metal industry.
In practice, Staacke believes it is important that the red fluorescence of varying intensity provides an easily interpretable output signal. “The physical relationships behind the measurement are highly complex. But changes in brightness can be easily understood by anyone, even without being a quantum physicist.”
A single measuring point is one of the simpler application scenarios. According to Staacke, scanning methods, for example with a moving sensor in the materials, are also relatively easy to implement. The idea of a quantum magnetic field camera is a bit more complex, but demonstrators for this have already been set up. Staacke explains, “We covered a larger area with diamond nanoparticles, excited them with an LED and then observed the red fluorescence using a CCD camera.”
Developing markets, gathering experience
Demonstrators for position and frequency measurement on rotating magnets for electric motor monitoring, as well as the Megapixel magnetic field camera, are intended to illustrate practical advantages to future customers of Quantum Technologies — as well as the wide range of potential applications. In order to accelerate the market entry process, the company entered into a partnership with reichelt elektronik just last year.
Their Head of Product Management and Marketing, Christian Reinwald, sees this cooperation as an opportunity to be part of an emerging technology segment at an early stage. “As a distributor, we are happy to support a startup with exceptional technological potential in opening up its industrial markets,” said Reinwald, commenting on the collaboration. At the same time, reichelt has the opportunity to gain initial experience in the application of quantum sensor technology. This is very valuable, as distribution customers will benefit from the findings in the future.
The QT DMFS-C2 quantum magnetic field sensor from Quantum Technologies is currently available through the sales program of reichelt elektronik. Equipped with multimode optical fibre and specified for operating temperatures from 15 to 25°C and for an excitation power of 5 mW, the robust and compact sensor is suitable for fully optical, galvanically isolated and isotropic measurement of magnetic field strength in the range of 0 to 75 mT. This simply requires an excitation light source for generating the fluorescence, and a photo detector for its observation — and no microwave radiation. In addition to the photodiode, suitable filters are required in the detector to suppress the excitation wavelength. These and other application requirements as well as the specifications of the quantum sensor are documented in detail at the distributor.
Conclusion: The next level of sensor integration
From the Leipzig research laboratory on industrial sensor applications: Robert Staacke and Quantum Technologies have managed to transfer complex quantum physics into a handy, user-friendly industrial product in just a few years. Its capabilities for robust and isotropic magnetic field measurement in the tightest of spaces will enable development engineers to integrate sensor technology in completely new measurement scenarios and in previously impossible applications in automation, automotive and medical technology. The partnership with reichelt elektronik is driving the market launch of quantum sensors and helping to deepen the application expertise associated with it.
Images: Quantum Technologies
