Researchers have successfully demonstrated a quantum sensor that can work with ambient magnetic field and sunlight; this can help reduce the energy costs associated with this energy consuming device.
Today, quantum sensors are used in various fields such as nanoscale magnetometry, gravitational wave detection and time measurement. Most researchers aim to build the most sensitive quantum sensors possible, which often requires the use of sophisticated-energy-consuming technologies. This high energy consumption can be problematic for sensors intended for use in remote areas of the Earth, in space, or in off-grid Internet of Things sensors. Yunbin Zhu of the China University of Science and Technology and colleagues have demonstrated a quantum sensor that directly uses renewable energy sources to get the energy it needs to work, reducing the need for external energy sources for quantum sensors.
This new device could significantly reduce the energy costs of quantum sensors in existing applications and expand the use of quantum sensors.
Today, research laboratories with almost unlimited access to energy are where most quantum technologies are discovered. Powerful lasers, microwave frequency amplifiers and waveform generators are needed for a conventional device to operate at cryogenic temperatures. A device like this can use thousands of watts and run continuously. Making sensors from systems that do not require cryogenic cooling, such as nitrogen-gap (NV) centers with diamond defects, is one method of reducing these energy costs. Such sensors still require a powerful laser that can use 100-1000 W and a microwave source that requires about 100 W.
The miniaturization of sensors, a procedure that normally reduces power consumption, is another area of research. But the latest iterations of these tiny sensors continue to use the grid for power.
Zhu and colleagues take a different strategy by creating a quantum sensor that generates its own electricity from a renewable energy source (in this case, solar energy).
The team's sensor is built from a collection of NV centers in diamond, a well-known solid-state quantum sensing technology that can operate in a variety of conditions, including high pressures (up to 40 GPa), low temperatures (0-600 K), and magnetic fields (0-12 T). Nitrogen ions are often injected into the diamond lattice to produce nitrogen vacancy centers, which are defects. A limited electronic state is produced by centers that trap charge carriers such as electrons or holes.
By laser-stimulating the defect, users can read the spin of this condition. Next, the NV center fluoresces, producing radiation whose strength is related to the spin of the system. Because green lasers have the largest fluorescence of the system, scientists often use them for this excitation.
Because NV centers operate at room temperature and do not need a cooling system, they are perfect for use in quantum applications. However, they need a laser to excite the NV core. The fluorescence frequency of the NV center can be bisected by adding a bias magnetic field, and the resulting two emission peaks can be accessed by sweeping the microwave amplifier over these frequencies. They also need a magnetic field generator and a microwave frequency amplifier. These peaks provide information about temperature and strain changes in the device, as well as any changes in the ambient magnetic field relative to the bias voltage.
The technology developed by Zhu and colleagues eliminates both the laser and the amplifier. The researchers filter sunlight using an optical band-pass filter so that only green wavelengths come in instead of laser light to activate the NV center.
They also use an iron device known as a flux concentrator to increase the Earth's magnetic field to 100 to 300 Gs. The energy nature of NV centers at certain magnetic field strengths allows purely optical detection of changes in the surrounding magnetic field by simply observing the fluorescence intensity of the device. With this feature, the team can drive a sensor without the need for an additional magnetic field generator or external microwave frequency amplifier.
The team's device only needs 0,1 W to operate, which is enough to power a photodetector with low energy consumption for spin reading. The researchers have shown that they can detect with remarkable precision changes in the Earth's magnetic field in ground level, caused, for example, by the presence of nearby power lines or trains.
This sensitivity is less than 1 nT/sqrt(Hz), comparable to that of diamond, which normally contains natural amounts of the two carbon isotopes C12 and C13. Higher sensitivity is achieved with isotopically pure, lab-grown diamond; the best is in the range of 1 pT/sqrt(Hz), which is suitable for detecting changes in biological magnetic fields in heart or skeletal muscles. I believe they can achieve such a level of precision by increasing the amount of sunlight penetrating the tool, or by adjusting the diamond's isotopic composition and concentration of NV centers.
This experiment represents the first step towards feeding quantum technology directly with renewable energy, eliminating the need for an external power source. By doing this, Zhu and colleagues show that their devices are significantly more energy efficient than similar grid-connected devices.
Source: physics.aps.org/
📩 19/10/2022 21:25
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