Quantum Sensing
Shashank V Raghavan??
Artificial Intelligence?| Autonomous Systems??| Resident Robot Geek??| Quantum Computing??| Product and Program Management??
Quantum Sensing is an advanced sensor technology that vastly improves the accuracy of how we measure, navigate, study, explore, see, and interact with the world around us by sensing changes in motion, and electric and magnetic fields.?
What are quantum sensors?
Quantum sensors measure minute changes in electric and magnetic fields as well as motion and the measurements are made at the atomic level. At this scale, information from individual atoms instead of from huge collections of atoms allows quantum sensors to make exponentially more accurate, more thorough, more efficient, and more productive measurements. Using the smallest amounts of energy and matter, quantum sensors can detect and measure the smallest changes in time, gravity, temperature, pressure, rotation, acceleration, and frequency as well as magnetic and electric fields.
Unlike quantum computing which has been discussed for years but is not available for public use, quantum sensing has been available for several decades in products such as magnetic resonance imaging (MRI) machines. Similarly, microwave atomic clocks and superconducting quantum interference devices (SQUIDs), have used quantum sensors for decades as well. The next generation of quantum sensing is just emerging. It includes gravity sensors, nitrogen-vacancy (NV) sensors, and other innovations. Next-generation applications fall into at least eight categories and differ regarding maturity levels and market potential.
How does Quantum Sensing work?
Collecting these “delicate” data at the atomic level often means extracting information from individual atoms instead of from the huge collections of atoms, as happens in classical physics. This allows quantum sensors to make our technological devices exponentially more accurate, more thorough, more efficient, and more productive. Devices that use quantum sensing are also not subject to the same physical constraints as conventional sensors, allowing for exceptional reliability with less vulnerability to the signal jamming and other electromagnetic interference that is increasingly common with today’s light- and sound-based data sensors.
What is Quantum Sensing used for?
Because quantum sensing measures activity in the physical world using atomic properties, the significantly more accurate data it provides can make future versions of technologies that already exist today function better, collecting and using better information to yield better results. Examples of using this in day-to-day life include:
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How does Quantum Sensing extract data at the atomic level?
Quantum Sensors use what are called “quantum resources” to measure changes in atoms with a higher degree of precision than any traditional measurement strategy can. Quantum resources are physical qualities that don’t exist in classical physics, including entanglement, quantum interference (a.k.a. superposition), discrete states, and coherence. For example, quantum optics typically relies on measurements using various aspects of light, or photons, but quantum sensors can also be made from other mediums, such as atoms in free space and certain solid state devices.
Who uses Quantum Sensing?
Just as GPS, radar, lidar, and other electromagnetic technologies use quantum physics to provide increasingly common tools on city streets, in aircraft, and on even basic cell phones today, Quantum Sensing is in the process now of shifting from being a highly-prized capability few know about to being in daily use everywhere tomorrow. Once it achieves widespread adoption, Quantum Sensing is expected to dramatically improve capabilities for:
Quantum sensors turn the inherent weakness of quantum technology - its instability against the environment - into a strength. It takes a huge amount of work to isolate a quantum system in a way that allows it to be used faithfully as a clock. Quantum sensors can detect and measure magnetic fields with previously unheard-of sensitivity and precision. In general, these quantum devices are REALLY sensitive to everything around them; the most sensitive experiments to date have shown that such clocks can measure the effect of lifting the clock by a bit more than one foot (gravity changes as you move away from the center of the Earth). But quantum sensors deliver more than just sensitivity - quantum sensors also give the benefit of stability over long times. Conventional sensor instruments slowly change over time, meaning that averaging longer to reduce measurement noise becomes impossible. But because quantum sensors use immutable quantities - like the structure of atoms - their measurements tend to be very stable over long times.
Exploring a Quantum Sensor: Atomic Clocks
Let’s explore one exciting kind of quantum sensor based on the same core technology as used in atomic clocks - cold-trapped atoms. Cold atoms can be exploited for ultra-sensitive interferometric measurements using the wavelike nature of matter. Instead of building interferometers with light reflected off of (matter-based) mirrors (as widely used in telecom optical modulators), one can build atom interferometers using matter “reflected” off of pulses of light. Such atom interferometers have the benefit that the atoms themselves have mass, making them sensitive to both gravity and general acceleration. Accordingly, there is an emerging area of work on quantum-enabled “PNT” or positioning, navigation, and timing. Here, atomic accelerometers may enable dead reckoning navigation in environments such as space or GPS-denied battlefields.
More broadly, leveraging these capabilities and advantages, atomic devices are routinely used for both magnetometry and gravimetry. They could thus be deployed by military personnel to detect underground, hardened structures, submarines, or hidden weapons systems. Imagine a detector which can measure via changes in gravity whether a mountain is being hollowed out in a hostile nation with a furtive weapons program. In civilian applications, these devices form the basis of new ways to monitor the climate - from underground aquifer levels through to ice-sheet thickness. Totally new forms of Earth observation for the space sector are now emerging, enabled by new small-form quantum sensors. Those capabilities flow into new data streams for long-term weather forecasting and insurance against weather events in agriculture. And of course, the mining industry has long relied on advanced instrumentation for improved aerial survey and productivity enhancement.
Of course, trapped atoms aren’t the only technology relevant to quantum sensing. There’s been a huge amount of research showing how solid-state devices like imperfections in diamonds can be used as sensitive magnetometers. These have the advantage that they can be used in biological environments - even in vivo. They may not be as sensitive as atomic devices, but by virtue of their tiny size, they can access new applications that are not possible with trapped atoms.
While the promise of Quantum Sensing continues to increase, the ability to apply it to solutions that can be implemented ahead of the curve requires development environments that support aggressive innovation. Given the broad appeal of the core technology, it is expected that much progress in the field will continue to be achieved through advantageous partnering to accelerate real world deliverables.