How Sensors Using Quantum Entanglement Could Improve Earthquake Detection

One of the scariest things about an earthquake is not how much damage it creates but when and where it will strike next. The start of 2023 has already brought significant tremor activity, with February quakes in Turkey and Syria killing tens of thousands of people.

Many experts predict this type of destructive earthquake activity will only continue, threatening other at-risk areas around the globe.

Although scientists cannot predict when an earthquake may strike, many are developing sensitive devices that could improve earthquake detection. One such device is the quantum sensor.

Suspending atoms at ultra-cold temperatures (near 0 degrees Kelvin) in laser arrays, quantum sensors can detect minute changes in gravity waves while becoming even more sensitive when quantum entangled.

While this setup offers more thorough data for improving earthquake models, it can be costly.

Current detection methods leverage a network of seismographs around the globe. At each network node, any tremor, or even a rock slipping, could trigger a measurement from the seismograph.

“Current systems are made up of accelerometers [seismographs] that detect the earliest seismic wave arrivals, which are pressure waves [p-waves] that move the ground but aren’t as destructive as subsequent shear waves [s-waves] which travel slower,” says Daniel Boddice, a professor at the University of Birmingham who has a Ph.D. in civil engineering.

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While these measurements can help triangulate the quake’s epicenter, they have significant limitations. “This gives some warning but means [seismographs] can't produce decisive event warnings because they only see something when the ground starts to shake,” Boddice adds.

In other words, the seismographs can only measure waves as the earthquake happens, forcing scientists into a race against time to warn at-risk areas before it is too late.

With quantum sensors, boosting the sensitivity to gravity waves can result in more data before a quake, giving valuable time for issuing a warning.

Combining groups of atoms and a web of lasers, scientists can monitor the fluctuations in individual atoms within this web, culminating in large amounts of accurate data.

Scientists are working on adding quantum entanglement to these sensors, where two particles within the apparatus would be entangled or have interdependent quantum states. When this happens, the atoms are less susceptible to environmental noise, giving more precise readings of gravitational wave fluctuations.

Although the entangled quantum sensors may not be plagued by the problems of traditional seismographs, such as signal jamming, they have their issues, mainly the flimsiness of the entire system.

Quantum entanglement is incredibly fragile and can break quickly. That makes the implementation and maintenance of such a system difficult and costly. But research is underway to make these systems more robust, especially for creating other devices like quantum computers.

Boddice is one of the many researchers looking into leveraging these quantum devices for an improved earthquake detection system.

“By adding a network of permanently monitoring gravimeter sensors, if you detected a mass shift caused by the plate movement on multiple detectors simultaneously, you’d have an earlier warning,” Boddice says. That could then be confirmed once the accelerometers started to detect wave arrivals as the gravitational signal travels at light speed.

Combining quantum sensors with traditional seismographs could provide more precise data for researchers to use in earthquake models, leading to better hot-spot predictions and more effective warning systems.

The sensitivity gained through this sort of quantum sensing “has the potential of saving thousands of lives by providing the critical extra seconds needed to reach safer locations at the onset of an earthquake,” says Anjul Loiacono, vice president of Quantum Signal Processing at Infleqtion (formerly ColdQuanta), a quantum computing company developing quantum sensors for gravitational wave detection.

Though the warning window may be expanded only slightly, Boddice believes that this extra time can still make a difference in reducing fatalities during an earthquake.

“For example, if a rail under a train buckles while the train is moving, it will crash; so it’s better to stop the train to avoid that impact,” he says. “You can take action to avoid people getting into riskier places.”

This might apply to the operation of elevators, or closing entrances to tunnels where people may get trapped when an earthquake starts. You could also shut off power and gas networks to avoid fires in the event of a rupture during a tremor.

“Individually these actions might seem like tiny things, but cumulatively for a big enough earthquake, they might make a significant difference to casualties,” Boddice adds.

While these devices can improve the warning time, they also may be too sensitive, which poses other challenges.

“The high sensitivity of the quantum gravimeters is both a blessing and a curse,” Boddice says.

That’s because all sorts of forces, such as vehicle traffic, send vibrations through the Earth that might register in these sensitive devices. This sparks the job of discerning the background noise from important but small gravity signals.

As a result, some scientists are turning to machine-learning algorithms. This technology can help interpret what is noise and what is an earthquake.

“Combining the power of machine learning with quantum gravitational sensing technology will lead to faster and more precise detection of imminent earthquakes,” Loiacono says.

Machine-learning algorithms can also help predict trends for future earthquake activity.

Current data shows a significant spike in the number of major earthquakes within the past two years, and experts predict that this trend will continue.

However, that increasing trend is largely due to the fact that detection abilities have increased, as well as reporting vigilance and the impact of earthquakes in more populated and developed areas.

“There’s a long history of detecting earthquakes, and they aren’t any more common now than in the past,” Boddice says. “I suspect a combination of more populated areas increases the chances of them being noticed or more reporting on them due to 24-hour rolling news.”

He suggests that an objective, comprehensive and long-term look at the trend would actually reveal they are no more common now than at any other point in time.

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