Quantum sensor is a physical device designed according to the laws of quantum mechanics and using quantum effects to transform the measured system. Quantum sensors use the extreme sensitivity of quantum states, but it is a great challenge to make them practical and practical.

1、 Definition of quantum sensor

How can a technology be considered quantum technology?

Researchers in the industry generally believe that technologies that follow the laws of quantum mechanics and use quantum effects such as quantum superposition and entanglement can be strictly regarded as quantum technologies.

In recent years, it has been found that higher precision measurement can be achieved by using the basic properties of quantum mechanics, such as quantum coherence, quantum entanglement, quantum statistics and so on. Therefore, the realization of high-precision measurement of physical quantities based on the characteristics of quantum mechanics is called quantum sensing. In quantum sensing, electromagnetic field, temperature, pressure and other external environments directly interact with electrons, photons, phonons and other systems and change their quantum states. Finally, these changed quantum states are detected to achieve high-sensitivity measurement of the external environment. The sensitivity of measurement can be further improved by using the current mature quantum state manipulation technology. Therefore, these quantum systems such as electrons, photons and phonons are a highly sensitive quantum “ruler” – quantum sensor.

The so-called quantum sensor can be defined from two aspects:

(1) A physical device designed according to the corresponding quantum algorithm to perform the transformation function using the quantum effect;

(2) In order to meet the transformation of the measured, some parts are so subtle that their quantum effects must be considered.

No matter from which definition, quantum sensors must follow the laws of quantum mechanics. It can be said that quantum sensor is a physical device designed according to the laws of quantum mechanics and using quantum effects to transform the measured system.

For example, quantum radar technology uses the principle of quantum entanglement. According to physicist Seth Lloyd’s theoretical scheme, this process involves bouncing half of a series of entangled photon pairs back from an object, and then comparing the returned photons with the blocked photons. The purpose of this is to distinguish the initial radiation from strong noise sources, find objects that cannot be detected by ordinary radar such as stealth aircraft, and hide the radar operator

Like the booming biosensors, the quantum sensor should be composed of two parts: the sensitive element generating the signal and the auxiliary instrument processing the signal. The sensitive element is the core of the sensor, which uses the quantum effect.

Characteristics and application analysis of quantum sensor

2、 Characteristics of quantum sensors

The performance and quality of the sensor are mainly evaluated from the aspects of accuracy, stability and sensitivity. Combined with the characteristics of quantum sensor, the performance of quantum sensor can be considered from the following aspects:

(1) Non destructive:

In quantum control, because the measurement may cause the reduction of the wave function of the measured system, and the sensor may also cause the change of the system state, the interaction between the quantum sensor and the system should be fully considered in the measurement. Because the state detection in quantum control is essentially different from that in classical control, the reduction process of state wave function caused by measurement implies that the measurement of state has destroyed the state itself. Therefore, non-destructive is one of the key aspects that quantum sensors should consider. In the actual detection, the quantum sensor can be considered as a part of the system, or the Hamiltonian of the interaction between the sensor and the measured object can be considered in the evolution of the whole system state as the disturbance of the system;

(2) Real time:

According to the characteristics of measurement in quantum control, especially the rapidity of state evolution, real-time has become an important index for the quality evaluation of quantum sensors. The real-time performance requires that the measurement results of the quantum sensor can be better consistent with the current state of the measured object, and can track the evolution of the quantum state of the measured object when necessary. When designing the quantum sensor, we should consider how to solve the problem of measurement lag;

(3) Sensitivity:

Because the main function of quantum sensor is to realize the transformation of micro objects, it is required that small changes of objects can also be captured. Therefore, when designing quantum sensor, its sensitivity should be considered to meet the actual requirements;

(4) Stability:

In quantum control, the state of the controlled object is easily affected by the environment, and the state of the object or the sensor itself may be unstable when the quantum sensor detects the quantum state of the object. The solution is to introduce the idea of environmental engineering and consider using cooling wells, low-temperature retainers and other methods for protection;

(5) Versatility:

Quantum system itself is a complex system. It is easy to interact between subsystems or between sensors and systems. In practical application, it is always expected to reduce the lag caused by human influence and multi-step measurement. Therefore, more functions, such as sampling, processing and measurement, can be integrated on the same quantum sensor, and appropriate intelligent control algorithms can be integrated into it, An intelligent and multifunctional quantum sensor is designed.

Quantum sensors have many properties that classical sensors do not have. When designing quantum sensors, we should not only focus on transforming the non measurable quantities in the quantum field into measurable quantities, but also evaluate the performance of quantum sensors from the aspects of non-destructive, real-time, sensitivity, stability and versatility.

3、 Application of quantum sensor

With the in-depth study of quantum control, the requirements for sensitive components will be higher and higher, and the development of sensors also has the trend of miniaturization and quantum type. Quantum effects will inevitably play an important role in sensors, and various quantum sensors will be widely used in quantum control, state detection and so on.

① . micro pressure measurement

The National Institute of standards and Technology (NIST) has developed a pressure sensor that can effectively count the particles in the box. The device compares the pressure of the vacuum cavity and the helium cavity by measuring the beat frequency generated when the laser beam passes through the helium cavity and the vacuum cavity. The small change of laser frequency in the gas to keep the resonant standing wave reflects the small change of pressure (because the pressure changes the refractive index).

The quantum pressure sensor, coupled with the first principle calculation of helium refractive index, can be used as a pressure standard to replace the bulky mercury manometer. It may also be used to calibrate pressure sensors in semiconductor foundries or as very accurate aircraft altimeters.

② Precise gravity measurement

Light measurement is not suitable for all imaging work. As a new alternative and supplementary means, gravity measurement can well reflect the subtle changes in a certain place, such as inaccessible old mines, pits and deep underground water and gas pipes. With this method, oil exploration and water level monitoring will also become extremely easy.

The new gravity sensor and quantum enhanced MEMS (micro electro mechanical system) technology developed by using quantum cold atoms have higher performance than previous devices and will have more important commercial applications.

A low-cost MEMS device is also being conceived. It is expected that it will be only the size of a tennis ball and its sensitivity will be a million times higher than the motion sensor used in smart phones. Once this technology is mature, it will be possible to draw large-area gravity field images.

MEMS sensors have made progress in quantum imaging readout by at least several orders of magnitude. Researchers from Glasgow University and Bridgeport University have developed a we-g detector. We-g is a MEMS based gravimeter, which is much lighter than traditional gravity sensors and may be much cheaper than traditional gravity sensors.

Characteristics and application analysis of quantum sensor

We-g sensors use quantum light sources to improve equipment accuracy, so that even smaller objects can be detected – or help rescue operations in avalanche and earthquake disasters, help the construction industry determine the detailed conditions underground, reduce project delays due to accidental hazards, and get rid of the dependence on expensive exploration and excavation.

In addition, conventional earth remote sensing observation can also be realized through accurate gravity measurement. The scope of monitoring includes the changes of groundwater reserves, glaciers and ice sheets.

③ Detection of radio spectrum by quantum sensor

U.S. Army researchers have developed a new quantum sensor that can help soldiers detect the entire radio spectrum – communication signals from 0 to 100 gigahertz (GHz).

The new quantum sensor is so small that it can hardly be detected by other devices, which is expected to make soldiers more powerful, such as communication receivers.

Although Rydberg atoms have broad-spectrum sensitivity, scientists have never described the sensitivity of the whole operating band quantitatively.

Compared with the traditional receiver, the new quantum sensor is smaller, and its sensitivity is comparable to other electric field sensor technologies, such as passive electronic devices coupled with electro-optic crystals and dipole antennas.

At present, army scientists plan to further refine the latest technology, improve the sensitivity of this quantum sensor, enable it to detect weaker signals, and expand the protocol for detecting more complex waveforms.

However, the imagination of quantum sensors is more than that: the development of quantum magnetic sensors will greatly reduce the cost of magnetic brain imaging and contribute to the popularization of this technology; The quantum sensor used to measure gravity is expected to change people’s impression that the traditional underground survey work is complex and time-consuming; Even in the field of navigation, the area that can not be searched by navigation satellites is the place where the inertial navigation provided by quantum sensors can be used.

④ , medical and health

Dementia: according to the Alzheimer’s disease association, the annual economic loss caused by dementia in the world is about 500 billion pounds, which is still increasing. The current diagnosis form based on patient questionnaire usually seriously limits the possibility of selecting treatment methods. Only early diagnosis and intervention can have better results.

Researchers are studying a technique called magnetoencephalography (MEG) for early diagnosis. However, the problem is that the technology currently requires magnetic shielding room and liquid helium cooling operation, which makes the promotion of the technology extremely expensive. The quantum magnetometer can make up for this defect. It has higher sensitivity, hardly needs cooling and shielding, and the key is its lower cost.

Cancer: a technology called microwave tomography has been applied to the early detection of breast cancer for many years, and quantum sensor helps to improve the sensitivity and display resolution of this technology. Unlike traditional X-rays, microwave imaging does not expose the breast directly to ionizing radiation.

In addition, the diamond based quantum sensor also makes it possible to study the temperature and magnetic field in living cells at the atomic level, which provides a new tool for medical research.

Heart disease: arrhythmia is usually regarded as the first fatal killer in developed countries, and the pathological feature of the disease is the irregular heart rate of fast and slow. At present, the magnetic induction tomography technology under development is regarded as a tool to diagnose fibrillation and study its formation mechanism. The emergence of quantum magnetometer will greatly improve the application effect of this technology, and will be of great benefit in imaging clinical application, patient monitoring and surgical planning.

⑤ , transportation and navigation

With the development of transportation, it is more necessary to understand the accurate location information and conditions of various means of transportation, which also puts forward requirements for the number of sensors carried by cars, trains and aircraft. Satellite navigation equipment, radar sensors, ultrasonic sensors and optical sensors will gradually become standard.

However, these are far from enough, and the development of sensor technology will also face new challenges. The positioning and navigation accuracy of the automatic driving vehicle and train is strictly within 10 cm. The next generation of driving assistance system must be able to monitor the local centimeter dangerous road conditions at any time. Using quantum sensors based on cold atoms, the navigation system can not only accurately position information to centimeters, but also have the ability to work in places inaccessible to navigation satellites such as underwater, underground and buildings.

At the same time, other types of quantum sensors are also developing (such as sensors working in terahertz band), which can accurately evaluate the road to the millimeter level. In addition, the laser based microwave source originally developed for the atomic clock can also improve the working range and accuracy of the airport radar system.

4、 How far is the quantum sensor revolution?

Many experts say that the world is on the verge of the second quantum revolution. Energy quantization has brought modern electronic technology to mankind through transistors and lasers. However, with the rapid development of human ability to manipulate single atoms and electrons, it may change industries such as communication, energy, medicine and national defense. This has triggered a special project with large funds in the United Kingdom and the European Union in order to seek to commercialize quantum technology. At the same time, the national quantum plan has recently been promulgated in the United States (the American Optical Society is the founding partner), and China and other countries will spend billions of dollars on relevant research in the next few years.

Dr. qudsiaquraishi, a physicist at the sensor and electronic equipment Bureau of the U.S. Army Research Laboratory, pointed out that the next generation of accurate sensing system involves quantum sensors. Quantum sensors are based on laser cooling atoms, which is likely to greatly improve the performance of the system. Laser cooled atoms are small coherent gas atoms, which can measure the changes of gravity field or magnetic field. They are not only very accurate, but also highly sensitive.

Many scientists engaged in quantum sensor research have set up companies to commercialize their technology, but few real products are on the market.

In fact, in quantum technology, what people talk about most is quantum computer. In theory, quantum computers are powerful and can crack the underlying code of Internet Security in just a few minutes. But the advent of full-scale quantum computers may take decades. In contrast, devices that use quantum phenomena to encrypt rather than crack passwords are beginning to appear on the market.

However, many scientists believe that quantum will achieve its first real commercial success in the field of sensing. This is because sensing can take advantage of a characteristic of quantum computers: quantum states are extremely sensitive to the environment, which is why it is so difficult to make quantum computers. Whether they respond to the gravity of buried objects or receive the magnetic field of the human brain, quantum sensors can detect all kinds of weak signals from the surrounding world. Kai bongs, a physicist at the University of Birmingham in the UK, said he believes that, in particular, the gravity measurement quantum sensor “will soon be more widely used”, and its potential market may reach US $1 billion a year.

Characteristics and application analysis of quantum sensor

However, in addition to some markets targeting opportunities, the competitiveness of quantum sensors remains to be seen. They are usually larger and more complex than their classic rivals – as Franck Pereira dos Santos of Syrte metrology laboratory in Paris points out, they have benefited from huge investments over the years. He believes that quantum technology is sometimes exaggerated by those who lack practical experience in manufacturing sensors.

However, the establishment of quantum theory is one of the most brilliant achievements in the 20th century. It reveals the structure, properties and motion law of matter in the micro field, and introduces people’s perspective from the macro field to the micro system.

Moreover, at present, high-precision quantum sensing of physical quantities such as electromagnetic field, temperature, pressure and inertia can be realized by using quantum systems such as electrons, photons and phonons. Experiments have demonstrated quantum super-resolution microscope, quantum magnetometer and quantum gyroscope, which are applied to the research of materials, biology and other related disciplines.

Therefore, although the realization of mass production of quantum sensors to the market will be difficult and long, it is believed that in the future, with the gradual maturity of relevant technologies, quantum sensors will be widely used in the national economy and the people’s livelihood.

Leave a Reply

Your email address will not be published. Required fields are marked *