The world, say many experts, is on the verge of a second quantum revolution. Energy quantization gave us modern electronics via the transistor and the laser, but humans’ burgeoning ability to manipulate individual atoms and electrons could potentially transform industries ranging from communications and energy to medicine and defense. The most talked-about of such technologies is the quantum computer, a device in theory so powerful that it could crack the codes underlying internet security in just a few minutes. But full-scale quantum computers are still potentially decades away. In contrast, devices that exploit quantum phenomena to encrypt codes, rather than break them, are starting to appear on the market.
Yet many scientists believe that quantum will enjoy its first real commercial success in sensing. That’s because sensing can take advantage of the very characteristic that makes building a quantum computer so difficult: the extraordinary sensitivity of quantum states to the environment. Quantum could be transformative, enabling autonomous vehicles that can “see” around corners, underwater navigation systems, early-warning systems for volcanic activity and earthquakes, and portable scanners that monitor a person’s brain activity during daily life.
Quantum sensing uses some nonintuitive properties of nature to measure things like time, magnetic fields, gravity, or acceleration. These sensors offer a particularly high level of sensitivity based on certain delicate quantum phenomena, such as quantum decoherence and quantum entanglement. Quantum sensors are measuring device that takes advantage of quantum correlations, such as states in a quantum superposition or entanglement, for better sensitivity and resolution than can be obtained by classical systems. For example, Quantum sensor exploit entangled quantum systems to make better atomic clocks or more sensitive magnetometers.
Quantum sensors include atomic clocks, single-photon detectors, PAR sensors, quantum LiDAR and quantum radar, gravity sensors, atomic interferometers, magnetometers, quantum imaging devices, spin-qubit-based sensors, and quantum rotation sensors, among others. Quantum sensing covers motion – including acceleration, rotation and gravity – electric and magnetic fields, and imaging. The benefits to quantum sensing include: Measuring electric and magnetic fields very accurately across many frequencies; Measuring physical quantities against atomic properties, so there is no drift or need to calibrate; Using quantum entanglement to improve sensitivity or precision.
Whether they are responding to the gravitational pull of buried objects or picking up magnetic fields from the human brain, quantum sensors can detect a wide range of tiny signals from the world around us. The applications for these sensors are also very broad, ranging from agriculture to stock trading to transportation to defense. A new generation of quantum sensors when developed will help to Map accurately buried hazards before rail, road and building projects begin; Make autonomous vehicles safe; Deliver crucial timing signals needed for electronic equipment, ending reliance on vulnerable and variable satellite signals; Set new standards for the operation of trading on financial markets and Reveal the invisible natural world underground and undersea.
Interferometry of atomic matter-waves has been demonstrated for the first time in orbit
A recent upgrade to NASA’s Cold Atom Lab has enabled atom interferometry on the International Space Station (ISS), forming the basis of a new generation of exquisitely precise quantum sensors that scientists can use to explore the universe. Applications of these spaceborne quantum sensors include tests of general relativity, searches for dark energy and gravitational waves, spacecraft navigation and drag referencing, and gravity science, including planetary geodesy—the study of a planet’s shape, orientation, and gravity field.
The wave-particle duality of matter is a cornerstone of quantum mechanics. First hypothesized by Louis De Broglie in 1924, it postulates that every particle or quantum object can be described as either a particle or a wave, depending on how we measure the properties of the object.
A natural consequence of the wave-like nature of quantum matter is that it can simultaneously exist in more than one place. When experimentalists measure the particle location, the simultaneous paths taken by the particle “collapse” to a single traceable trajectory. Quantum interferometry starts with particles in the same lowest energy state and then puts some of them in the first excited state and measures the phase difference between these two groups after they traverse a region of interest. Matter-wave interferometers have been experimentally demonstrated on Earth with numerous types of particles, including electrons, neutrons, atoms, antimatter, and even biomolecules.
View of the atom interferometry-capable Science Module inside two layers of magnetic shields during the pre-launch build/testing phase at JPL.
Over the last few decades, technology advancements have enabled cooling of atoms to temperatures below 1 microKelvin to form a fifth (purely quantum) state of matter called a Bose-Einstein condensate (BEC), making ultracold atom interferometers using this unique matter a leading candidate for future precision sensing of inertial forces. Analogous to high-precision optical interferometers (such as the Laser Interferometer Gravitational-Wave Observatory [LIGO], which recently detected gravitational waves using highly stable optical waves), atom interferometers with BECs utilize extremely pure, low-velocity quantum gases to achieve high-precision, phase-sensitive measurements of fundamental forces including gravity. They also promise to deliver unprecedented acceleration and rotation sensitivity for inertial navigation. In fact, such atom interferometers are shown to be sensitive enough to detect variations in a gravitational field, and thus could be used to map the interior density of planets.
Achieving atom interferometry in space had been a long-sought goal of NASA and the fundamental physics community. “The promise of very low temperature gases and effectively limitless free-fall time for space-based atom interferometry is expected to open a new regime of precision for inertial force and rotation measurements that could revolutionize both contemporary gravity science and spacecraft navigation capabilities in the near future,” said Dr. Jason Williams, a Principal Investigator for atom interferometry studies onboard ISS.
In May 2020, atom interferometry with an ultracold BEC of rubidium atoms was demonstrated for the first time on an orbiting platform. This experiment was realized by NASA’s multi-user Cold Atom Lab (CAL), which has been operating onboard the ISS since 2018. In January 2020, CAL received a Science Module capable of atom interferometry as part of an on-orbit upgrade. For the May 2020 demonstration, a laser pulse acted as the beam splitter for an atomic wave packet. Subsequent laser pulses then recombined the atoms and mixed them to produce an interference pattern which was read out by taking pictures of atoms occupying the spatially separated outputs. This demonstration of matter-wave interferometry in space heralds a future in which space-based quantum sensors become a widely used tool for scientific exploration of the universe. Applications of the new technology include tests of general relativity, searches for dark energy and gravitational waves, spacecraft navigation, and prospecting for subsurface minerals on the moon and other planetary bodies.
The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). Images courtesy of NASA/JPL-Caltech. Designed and built at JPL, Cold Atom Lab is sponsored by the Biological and Physical Sciences (BPS) Division of NASA’s Science Mission Directorate at the Agency’s headquarters in Washington DC and the International Space Station Program at NASA’s Johnson Space Center in Houston, Texas.
A quantum compass
Atom interferometers could also be used to build navigation devices that continue to work even when contact with GPS satellites is lost, as can happen in a tunnel or, more ominously, when signals are deliberately jammed. Keeping on course in this way relies on dead reckoning, the use of accelerometers and gyroscopes to continuously update a vehicle’s position, orientation and velocity with respect to a known starting point.
Like spring gravimeters, conventional accelerometers experience drift, as their pendula warp over time. In contrast, quantum accelerometers—essentially gravimeters with their laser beams flipped along the acceleration axis—are very stable. Although the atoms’ finite free-fall time and need for preparation prevent continuous operation, which is often provided by conventional accelerometers, they enable proper calibration.
Quantum gyroscopes, meanwhile, work by generating a phase difference between atom waves propagating in opposite directions around a rotating ring. Such technology has been developed by AOSense, a company in Sunnyvale, Calif., USA, set up in 2004 by atomic physicist Mark Kasevich and two colleagues at Stanford University, USA. Often working with the U.S. military, the firm built prototype gradiometers, gyroscopes and accelerometers for the Defense Advanced Research Projects Agency (DARPA). The aim, according to a 2014 story in Physics Today, was to make inertial measurement units that could fit on a fingertip. But in the end, Kasevich says, the necessary lasers and optical modulators couldn’t be made small enough to shrink gyroscopes below “about 100 cm3.”
Undeterred, physicists at Imperial College in London and the Glasgow-based company M Squared have built what the college describes as “the U.K.’s first commercially viable quantum accelerometer, which could be used for navigation.” OSA Fellow Ed Hinds of Imperial says that the roughly cubic-meter-sized device is about 1,000 times more stable than conventional accelerometers, and should be tested on a canal boat later this year.
It is not yet clear, however, whether the technology really is commercially viable. Being developed to guide submarines of the British Royal Navy, the complete navigation system will require another two accelerometers and three gyroscopes. Hinds says that the gyroscopes will be “much harder” to build than the accelerometers, and adds that reducing the device’s size and weight “are not the pressing issues.”
Jay Hendricks, head of a team at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., USA, which has built a pressure sensor that in effect counts particles in a box. The device compares the pressure of cavities containing helium gas and a vacuum by measuring the beat frequency generated by laser beams fired through them. Tiny changes made to the laser frequency in the gas to maintain a resonant standing wave reflect minuscule variations in the pressure (since pressure alters refractive index). “This is one step back from truly quantum, but is based on principles that can be quantized,” he says.
Together with first-principles calculations of helium’s refractive index, Hendricks says the device, known as the fixed-length optical cavity, could serve as a pressure standard to replace bulky mercury manometers. It might also be used to calibrate pressure sensors in semiconductor foundries or as a very precise aircraft altimeter, he adds. Working with MKS Instruments of Andover, Mass., USA, his group has shrunk the cavity length to just 2.5 cm and squeezed the ancillary equipment into a couple of suitcase-sized boxes—although he can’t say when a fully marketable device might emerge. figureThe Wee-g, a MEMS-based gravimeter that is far lighter and potentially much cheaper than conventional gravity sensors, could reach a sensitivity of 1 part in 109 by using squeezed light to overcome laser shot noise. [Richard Middlemiss]
Back in Glasgow, a group of physicists is using quantum technology to enhance a gravimeter known as “Wee-g”—even though the sensor itself has nothing to do with cold atoms. The microelectromechanical-system (MEMS) device consists of a 12-mm-long piece of silicon suspended by four extremely thin springs. The instrument’s sensitivity, according to team member Richard Middlemiss, is “within an order of magnitude” of existing gravimeters. It is also very light (perhaps making it suitable for drone surveys), and might cost little more than £1000 (about US$1300) once the wafers are mass-produced, he says.
Middlemiss believes that the sensor could hit the market within about a year, after some 30 to 40 units have been deployed on Mt. Etna in Italy to monitor magma movement. That version of the device will use capacitors to track the tiny test mass, but later incarnations could use a laser-based technique known as squeezing to overcome shot noise, potentially raising Wee-g’s sensitivity to 1 part in 109, he says. (For more on squeezed light in quantum sensors, see this issue’s tutorial “Better Sensors via Squeezed Light.”)
Engineering Challenges Remain
The latest advancements in atomic magnetometers have opened new growth opportunities for the market. The fact that magnetometers are used for detecting the interaction between the magnetic field and the alkali metal atoms and have the capability of detecting impurities in magnet will also help this market gain impetus in the forecast period.
On the contrary, design issue that engineers face and the need to regularly heat the magnetometer sensor vapor cell before performing operations may hamper the growth of the market. Nevertheless, the fact that these devices can eliminate the chances of any interference during magnetic imaging is expected to help this market attract high revenue in the coming years.
As magnetometers are integrated into various devices and equipment, however, engineers continue to face challenges due to complexities in designing the features of magnetometers such as noise fluctuations, linearity, and sensitivity, caution the TMR analysts. Minor deviations in GPS that use magnetometers for forecasting natural disasters can give out error-prone and misleading information. Temperature differences, and the presence of both soft and hard iron can lead to biases. A magnetometer reading can be distorted by ferromagnetic parts and associated electric equipment. In soft iron distortion, alternations or deflections arise in the existing magnetic field. If hard iron distortion occurs, such as from a speaker or magnetized piece of iron, it can result in permanent bias in the sensor output.
Quantum Sensor Manufacturing
Making atomic sensors competitive with existing technology is “a struggle,” according to Kasevich, because the subsystems that they rely on, such as lasers and vacuum chambers, are large and complex, and have not had their costs driven down by mass markets. Trying to shrink gyroscopes in particular incurs “crazy development costs,” says Pereira Dos Santos. One option would be to guide rather than drop atoms, but that, he says, is “very exploratory … and it might never work.”
Most quantum-sensing systems remain expensive, oversized and complex, but a new generation of smaller, more affordable sensors should open up new applications. Last year researchers at the Massachusetts Institute of Technology used conventional fabrication methods to put a diamond-based quantum sensor on a silicon chip, squeezing multiple, traditionally bulky components onto a square a few tenths of a millimeter wide. The prototype is a step toward low-cost, mass-produced quantum sensors that work at room temperature and that could be used for any application that involves taking fine measurements of weak magnetic fields.
But another type of quantum technology has simple subsystems and can be built using standard materials-science techniques: nitrogen–vacancy (NV) centers. These are atom-like defects in a synthetic diamond crystal consisting of a nitrogen atom and a gap in place of two carbon atoms. NV centers can emit red light when excited by green, but the probability of doing so depends on the spin states of their electrons. By placing the spin states in a superposition, microwaves with just the right frequency can change the emission intensity.
Crucially, this quantum state can persist for up to a millisecond at room temperature, thanks to the stiff diamond lattice that shields the NV centers from vibrations. And, because changes in the local magnetic field will change the spacing of the spin states and knock the microwave frequency off-resonance—with the change proportional to the field strength—NV centers could potentially make extremely sensitive magnetometers. The system is also sensitive to variations in electric field, strain and temperature, as these change the distance between atoms and, again, shift the resonance.
Several start-up companies are looking to commercialize NV technology, in areas such as biomedicine (see “Probing neurons and tumors,” p. 30), while some multinationals are also entering the fray. These include the German engineering giant Bosch, which is building a prototype NV sensor to monitor charging and prevent excess currents in car batteries. The French electronics company Thales, meanwhile, is applying magnetic field gradients across NV diamond crystals to identify frequency components in unknown microwave spectra.
According to Thales’ head of applied quantum physics, Thierry Debuisschert, 5G network operators could use this technology, for example, to prevent interference between neighboring cell towers. But he says that it will likely take several years to overcome technical and commercial obstacles, such as working out how best to collect the faint red light emitted by the crystal. Likewise, Bosch researcher Robert Roelver says that his company probably won’t market a device for another five to ten years.
Researchers at U.S. defense firm Lockheed Martin also face hurdles in commercializing an innovative navigation instrument. The roughly foot-long NV-based device navigates by picking up tiny anomalies in the Earth’s magnetic field that have previously been mapped. Project leader Michael DiMario explains that more than five years of work have yielded “very promising results” on land, at sea and in the air—but also unforeseen problems. “I can’t really say when it will go to market,” he says.
The atomic magnetometers market is fragmented in nature on account of the presence of multiple players. Some of them are Sinclair Research Center, Inc., The University Of New Mexico, University of California, Lawrence Berkley National Laboratory, Intel Corporation, Singer Company, Charles Stark Draper Laboratory, Inc., Conon, Inc., Georgia Tech Research Corporation, Southwest Sciences, Inc., Varian Associates, Sinclair Research Center, Inc., Sandia National Laboratories.
Most of these players are investing massively in research and development and the production of atomic magnetometers. Government support for these activities, coupled with the availability of suitable infrastructure is also helping these companies gain a competitive edge in the market.
The global magnetometer market is fragmented and witnessing an upsurge in competition, owing to rapid shifts and advancements in technology. Leading manufacturers of magnetometers such as Bartington Instruments Ltd, Cryogenic Ltd, Honeywell International Inc., and Gem Systems Advanced Magnetometers, account for about 30% revenue share of the magnetometer landscape with their robust collaborative strategies and penetrative distribution channels, reports TMR.
Ruling the roost is Bartington Instruments, a UK-based company displaying prowess in high precision magnetometers. A key behind its colossal global expansion is its vast distribution channel, with its arms reaching out across Europe and as far as Asia Pacific, say the TMR researchers. The company is a leading developer of sophisticated products for all major magnetometry markets.
In May 2019, Bartington re-launched the 3-axis Mag-13X fluxgate sensor with a temperature sensor and an electric shield that is designed to reduce emissions, thus making it more viable environmentally. Being used in bio-medicine and data storage, this re-launched product addresses the special needs of complex sensors in the consumer electronics and automotive industries. It is part of the company’s line of Mag-13 magnetometers, shown above is the Mag-13MS 100.
In September, a Bartington Spacemag magnetometer was scheduled to be launched into low Earth orbit, as part of UPM-SAT2 Union, a micro-satellite designed for academic and scientific applications. Created by a team at Universidad Politécnica de Madrid, the satellite was to be launched aboard a Vega rocket in French Guiana. Only a few months earlier, the Oculus-ASR satellite was launched from the Kennedy Space Center in Florida carrying Bartington’s Mag-03MRN 3-axis magnetometer, making it the largest satellite yet with a Bartington magnetometer aboard.
Standing second in market share, according to TMR, is Cryogenic. Headquartered in London with revenue of $12.8 million in 2018 and growing robustly, it has emerged as a leading market player due to its highly sensitive magnetometers. Its SQUID magnetometer has a very intricate internal design which keeps the magnet circuitry at a steady temperature, and makes it stand out in an intensely competitive market, says TMR.
Demand in electronics, healthcare and archeology Increasing
The demand for magnetometers has increased significantly across industries such as consumer electronics, healthcare and industrial archaeology, owing to the versatile roles they play in various industrial applications. Technological breakthroughs such as the development of miniature optical magnetometers are driving future growth in healthcare, notes TMR. Human organs such as muscles, brain, heart and even a single nerve produce a magnetic field that can be measured by these magnetometers which can lead to resolving a myriad of health issues. Wireless, wearable magnetometer-based sensors have changed the way sleep can be monitored. Transformative methods to detect the crucial sleep parameters of patients suffering from sleep apnea can be achieved by examining variations in the Earth’s magnetic field.
Magnetometers can provide turnkey solutions by their usage in cell phones and tablets. With their noise filtering capabilities, incredibly dynamic ranges and reduced power consumption, they will continue to find applications in the consumer electronics landscape in the coming years, says TMR.
The global atomic magnetometers market is expected to gain momentum on account of its low maintenance, initial, and labor cost. Atomic magnetometers are devices used for detecting sensitivity in magnetic fields and is used in a large number of applications such as detecting biomagnetic fields in relation to the human brain or locating underground structures that are unexploded. The increasing number of mining activities may also add boost to the growth of this market.
Long hailed for its widespread use in scouring the Earth’s magnetic field, the adoption of magnetometers has effectively resonated in various industrial applications that involve geophysical surveys and detecting magnetic anomalies. With the ever-expanding range of industrial applications of magnetometers, end users are voicing demand for advancements in their features, such as improved sensitivity, accuracy, and precision.
With the advent of emerging technology, reports TMR, manufacturers in the magnetometer market are focusing on enhancing the quantum properties of atomic sensors to improve the sensitivity and speed of magnetometers, and ultimately improve their efficiency in industrial applications. Ongoing research and development in quantum technologies is expected to contribute toward improving the sensitivity and precision of magnetometry measurements, enabling market players to stand out in the competition with high-performance magnetometers.
The magnetometer market has gained momentum and its landscape is growing fast, says TMR, owing to the rapidly changing and dynamic environment that has promulgated their use for the detection of mineral deposits, coal exploration, and identifying precious archaeological artifacts, along with their inclusion in consumer electronics, healthcare and aerospace industries. Most of the content of this article is from TMR’s report summary which is available in full on their website.
The atomic magnetometers market is categorized on the basis of product, channels, end users, application, and region. In terms of product, the market is classified into cold atomic magnetometers, and spin-exchange relaxation-free (SERF) magnetometer. In terms of channel, the market is bifurcated into direct sales and distributor. Based on end users the market is classified into medical, biological, and others. With respect to application, the market is divided into nuclear magnetic resonance, and magnetic resonance imaging. The market is expected to attract high revenues from the SERF segment as these magnetometers eliminates the decoherence of atomic spin as a result of spin-exchange collisions among the alkali metal atoms and is better than the traditional magnetometers in terms of both performance and efficiency.
While all quantum magnetometers offer users enhanced sensitivity compared with classical magnetometers, there is growing competition in the field between optically pumped magnetometers, proton magnetometers, Overhauser magnetometers, SERFs, NV-diamond vapor cell magnetometers and SQUIDs. For example, beyond medical imaging, the extreme sensitivity of SQUIDs makes them ideal for biological investigations of various kinds. And NV-diamond center magnetometers are being used in navigation systems where conventional GPS won’t work. A detailed assessment of the commercial potential for such novel systems is also included in this report. Quantum magnetometers have a large number of applications in the military. Both researchers in the US and China are working on such applications and this report discusses the impact that an era of Sino-American tensions may have on the quantum magnetometer business.
The demand for magnetometers is likely to remain comparatively higher in developed regions such as North America and Europe, holding a formidable revenue share of the magnetometer market, and continuing their dominance especially in the area of consumer electronics. Though the market is likely to stabilize in the US and Canada, the market for magnetometers in Europe is growing at a fast rate. European countries including Germany, UK and France are expected to account for one-third revenue share of the global magnetometer market, mainly attributing to the presence of key market players, their penetrative reach across the region, and the heavy funding and investments done in the semiconductor and medical industries there.
Magnetometers are one of the most integral components used in the aviation industry and spacecraft telemetry for developing spacecraft magnetic cleanliness designs. The use of magnetometers in aviation is not restricted to Global Positioning System (GPS) monitoring and tracking, but also involves their application in Unmanned Aerial Vehicles (UAVs) for aerial mapping and investigation. These are some of the key trends that are boosting the sales of magnetometers in the aerospace industry.
The aerospace and defense industry generated over one-third of the total revenue of the global market for magnetometers in 2018, and this demand will only get amplified in the coming years. Ongoing advancements in technologies are enabling manufacturers to improve the performance characteristics of magnetometers to suit the specific requirements vis-à-vis their applications in the aviation and defense industries.
Aerospace and defense end-users are showing preference towards the adoption of three-axis magnetometers with unique variable permeability properties, along with excellent noise performance, high sensitivity, and good linearity. Leading stakeholders are likely to increase their focus on capturing the opportunities pertaining to the integration of magnetometers with UAV technology.
In addition, OEMs and magnetometer suppliers stand to hugely profit due to substantial investments in arenas such as crop monitoring, infrastructure inspection and accident analysis. Increasing use of drones in land mining, farming and construction will spearhead the sales of magnetometers in these industries, says TMR.
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