Beyond qubits
The other waves of quantum technology
UNESCO, as I mentioned in my last post, designated 2025 as the year of quantum science and technology. This was appropriate because the science of quantum mechanics turns 100 this year, and for a century now we’ve had to live with the mind-bending concepts of entanglement, superposition and uncertainty. At the start of my journey into quantum a few years ago, I read Carlo Rovelli’s magnificent book Helgoland; upon finishing it, I came to the uncomfortable conclusion that we can’t really talk about solid objects in any meaningful way. Instead, I had to accept that matter at its most fundamental level is best thought of as a set of mathematical equations, waves and probabilities.
And yet, from this almost incomprehensible, ethereal unreality have come many of the technological advancements we take for granted in everyday life. Quantum technology is often described in three waves. The first wave consists of the many quantum innovations that were developed before quantum computing and the idea of encoding information in qubits. Quantum computing and qubits form the second wave, and I’ve covered these in some detail in many of my previous posts. The third wave refers to the inventions coming after quantum computing, in particular quantum telecommunication and sensors. In honour of UNESCO’s designation, let’s look in more detail at the oft-neglected first and third waves of quantum.
Wave one: the familiar
As I write this article, I can use my fingers to move the page up and down on my laptop screen, or enlarge an image, in exactly the same way as I would scroll on my iPhone. From kiosks to ATMs and computers to smart phones, we take touch screens for granted. I’ve heard of babies and toddlers, exposed early to tablets, trying to swipe their fingers over pages in a conventional printed book—the action is so intuitive. But have you thought about how it works with such precision? The touch screen uses a quantum effect called tunnelling, in which a particle like an electron can jump through a non-conductive barrier.
Well, it doesn’t really jump—tunnelling only works if the barrier is very thin, and you have to view a collection of particles not as solid masses, but as a Schrödinger wave equation. (Remember what I said before—matter is really just mathematics.) If the wave and barrier interact, parts of the wave may be on both sides and, presto—some of the electrons might be on the other side of the barrier.
A touch screen is composed of two layers of non-conducting material, with tiny spike-like conductors embedded in them. When you press your finger on the screen, you bring the layers closer together. Although the conducting spikes don’t actually touch, they get close enough that some electrons tunnel, establishing a current that allows your tap or swipe action to proceed. From now on, whenever you use your phone, remember that it’s a highly sensitive quantum device—just not a quantum computer.
Here's another example from wave one: I’ve always had very poor eyesight and was teased as a kid for wearing glasses with “coke-bottle” lenses. So, in my mid-forties I finally decided to do something about it and opted for the popular laser eye surgery. Although the faint smell of burning was a bit disconcerting, the procedure was not at all uncomfortable and it gave me more than a decade of 20/20 vision. From precision surgery to compact disc players to industrial applications and even data transmission, the laser—an early quantum technology—is everywhere.
LASER, of course, is an acronym that stands for Light Amplification by Stimulated Emission of Radiation. What does that mean? A laser beam is a highly focused emission of photons, all travelling at the same wavelength. This is what gives the beam its unique colour and narrow focus, as distinct from normal white light which is diffused and at multiple wavelengths. The laser beam is generated by applying energy to a material contained in a chamber—the choice of material will determine the wavelength of the emitted beam. The energy causes the atoms in the chamber to become excited; in their excited state, electrons jump between orbits and, when they do, they emit photons. This emission of photons is one of the first quantum effects studied by Niels Bohr and Werner Heisenberg in the 1920s. With enough energy, a chain reaction of photon emission takes place, is reinforced and focused by mirrors, and the beam is emitted from one end of the chamber.
For a final example, if you install solar panels on your roof, you can use the electricity generated to power your house and even sell surplus electricity into the local power grid. At industrial scale, we also see solar panels in fields along the highway virtually everywhere, supplying green power to the grid. Albert Einstein was awarded the Nobel prize in physics in 1921 for his discovery of the photoelectric effect that makes solar panels work. When photons from the sun’s rays strike the semiconducting material in the panels, they dislodge electrons, causing a current to flow. Come to think of it, it’s kind of the inverse of how a laser works—where an electrical current causes emission of photons. The solar panel has been around for decades, and the technology has been refined quite a bit over the years, incorporating other quantum effects like tunnelling and quantum dots, but the basic principle is the same.
Wave three: can we talk?
Interest in quantum communication has grown rapidly since Shor’s algorithm proved that classical data communication is vulnerable to attack by quantum computers. Many organizations are now implementing NIST’s newly approved key generation algorithms which should render current encryption key management systems quantum-resistant. However, there’s no guarantee that the new algorithms, based on more complicated mathematical problems, will be safe forever—there’s always the risk that some future quantum computer might render them just as vulnerable as prime factorization is to Shor’s algorithm.
So, some of the most interesting research in quantum applications today is in quantum communication. Instead of enhancing existing classical communication protocols, the vision is to create a whole new and more secure way of transmitting data using quantum mechanics—in particular, quantum entanglement with the related phenomenon of quantum teleportation.
Now, don’t start envisioning Star Trek-style transporters instantaneously moving people back and forth between a spaceship and a planet. Quantum teleportation implies only moving information between entangled quantum particles. The idea is that if two qubits are entangled, and one is moved some distance away, a change in the state of the first qubit implies the same change in the second. The communication is accomplished by combining a qubit carrying information with the first entangled qubit. In theory, the second entangled qubit can then receive the data. The technique is directly applicable to generating and exchanging better cryptographic keys, known as Quantum Key Distribution (QKD), and more generally transmitting data, known as Quantum Communication (QC).
The security of QKD and QC is derived from the quantum principle that when you observe or measure a qubit, it immediately decoheres into a value of zero or one. So, if a hacker were to intercept and try to read a message being transmitted, the sender and receiver would know that the transmission was compromised, and they would generate new keys to start over.
At first glance, given that quantum mechanics suggests that the entangled particles can be arbitrarily far apart, you would think that information might be able to travel faster than the speed of light. Einstein would turn in his grave if that were the case, and it turns out that some classical non-quantum information—typically, two classical bits for each qubit of information—needs to be transmitted separately to enable the second entangled qubit to reconstruct the data. Therefore, quantum communication via teleportation requires a classical communication channel (think fiber optic cable, or a laser beam) in addition to the entangled qubits, thus ensuring that the speed of light is not broken.
If all this sounds a bit far-fetched, well, it is and it isn’t—much of quantum communication is still in the experimental stage, but some significant advancements have already been announced. QKD is well established with vendors like EvolutionQ in Canada providing products and services now. In late 2023, researchers in China and Russia announced a successful transmission of images via quantum communication over a distance of 3,800 kilometers via a Chinese satellite in low earth orbit. Analysts predict quantum communication to become a $5.54 billion market by 2030.
Wave three: all the feels
My wife and I have been regular Volvo customers since expecting our first child more than two decades ago, and we’ve been quite happy with their safety and value. But I have noticed that Volvo, leading in many technical innovations, has experienced its share of glitches with on-board sensors in their vehicles.
Our 2003 XC70, for example, would occasionally and inexplicably slow down to less than 20 Km/Hr. and then refuse to accelerate, no matter how hard I pressed the pedal. After multiple trips to the repair shop—under warranty, of course—the company replaced the entire accelerator and throttle assembly and downloaded a software refresh to the car. A malfunctioning sensor in the accelerator pedal, which communicated with the car’s electronic throttle, traction and stability control, and crash avoidance systems, was at fault. A few years later we upgraded to an XC90, one of the first to be equipped with blind spot sensors. These worked OK in dry conditions but lit up continuously any time it rained, which wasn’t particularly useful. Our current XC90, some six years old now, has 360-degree proximity sensors which can be useful for parking or driving in traffic, but they frequently fire even when there are no obstacles anywhere near the car.
Automotive is one of the largest applications of sensor technology, and my experience shows that classical sensors, often based on cameras and radar, are not always sensitive enough. So, manufacturers are researching quantum technology to improve the accuracy of sensors throughout the vehicle.
If you’ve noticed prototype autonomous vehicles on the road lately, they often have a cylindrical module protruding from the roof. This is the Light Detection and Ranging (LiDAR) sensor, which operates by sending out laser pulses and measuring the beams reflected back to the car. It is still experimental and can be fooled by dust, raindrops or even another LiDAR-equipped car nearby but holds the promise of being able to give self-driving cars an accurate 360-degree view of their surroundings. LiDAR sensors can also be found in other devices from drones to robot vacuum cleaners.
And that wonky gas pedal sensor I experienced? Well, as cars evolve, the problem might go away—EVs don’t need a throttle, spark plugs or gear box—but they do need to precisely monitor the electrical current and battery life. An article in the online journal Advanced Science News describes some interesting work being done to develop ultra-sensitive diamond quantum sensors for EV batteries. A synthetic diamond with nitrogen inserted into the carbon crystals can be used to sense tiny fluctuations in electromagnetic fields. This will be helpful in monitoring for anomalies like overcharging or overdepletion, which can affect the battery life and reliability.
My next car will very likely be an EV, and probably a Volvo, so I will find out soon enough if the company will continue its leadership with quantum sensors.
The applicability of quantum sensors goes far beyond automotive, of course. The Canadian government recently updated its 2023 national quantum strategy to include a section devoted to quantum sensing. It lists many applications of quantum sensors in fields from oil and mineral exploration to agriculture to healthcare. All three are critical sectors in the Canadian economy, so let’s look at some examples.
In a previous article, I referred to work done by IBM in applying quantum genetic algorithms to geographical and seismic analysis in oil and gas exploration. Besides the computational benefit in analyzing reams of data, quantum technology is also being applied to the sensors used to do the exploration in the first place.
Geological sensing is often done by measuring minute changes in gravitational forces caused by changes in the structure of subterranean rock, which in turn will yield clues about oil or mineral deposits. Gravitational sensors (gravimeters or gravity gradiometers) have been around since the late 19th century when they were built of pendulums. Now, quantum gravimeters are under development, using Louis de Broglie’s wave theory of atomic particles. (Once again, thinking of matter as mathematics becomes useful.) The principle is atom interferometry, in which the effects of gravity on atoms can be measured by looking at the interference pattern produced by different atoms’ de Broglie waves. Higher-precision quantum sensors will yield much more accurate subterranean maps and therefore more efficient resource extraction.
Photosynthesis is, fundamentally, a quantum phenomenon in which a chlorophyll molecule ejects an electron when it is struck by light in the form of photons. So, it should be no surprise that quantum sensing is very popular in agricultural applications.
One example is the Photosynthetically Active Radiation (PAR) quantum sensor, which acts as a highly calibrated miniature solar panel. As far as plants are concerned, not all light is equal—only light waves within the spectral range of 400 to 700 nanometers[1] is useful for photosynthesis. The quantum PAR sensor measures light within this range, generating an electrical current proportional to the intensity of light received. Farmers and horticulturalists can use data from the sensor to improve growing conditions and manage plant health. For example, they can optimize crop placement in an outdoor field or make precise adjustments to light settings in a greenhouse, thereby maximizing plant growth and crop yields.
Last year, when I injured my knee while running, my doctor scheduled me for an MRI to determine the problem. Later, reviewing the images with the orthopedist, I was amazed at the detail shown, identifying a small tear in the meniscus as well as various effects of arthritis[2]. Magnetic Resonance Imaging is an example of NMR, Nuclear Magnetic Resonance, a quantum sensing technology that determines the inner structure of an object by measuring the wavelengths of individual atoms or molecules—hence the term resonance, and for the third time in this article, a reminder that matter is mathematics. MRIs can provide detailed imaging of objects as small as a human hair.
According to an article in Nature, researchers in Stuttgart and at IBM’s Almaden laboratory are taking NMR technology to the next level of precision. By adding diamond-nitrogen quantum sensors (exactly as used in EV battery monitoring) they expect to be able to detect nuclear resonance in objects only a few nanometers in size. Future applications may include inserting a quantum diamond sensor directly into a single cell and generating real-time views of the molecular activity within the cell.
Beyond the quantum century
UNESCO’s designation of 2025 as the year of quantum science and technology is just the beginning. In these articles I’ve only been able to illustrate a few examples of quantum technology—there’s a lot more to the three waves—but I think the impact is clear. The past century of quantum research and innovation has already touched every aspect of our lives—the energy and natural resources we consume, how we move around, what we eat and how we stay healthy.
Richard Feynman famously said that if you think you understand quantum mechanics, you don’t understand quantum mechanics. I’d go on to say that it’s OK if we don’t understand it—I certainly don’t pretend to—but if we accept and get comfortable with the key concepts, we will have a better understanding of the world around and within us.
I also won’t pretend to know what the next year, let alone the next century, holds in store. But that uncertainty, quantum or otherwise, is exciting, isn’t it?
[1] A nanometer is one millionth of a millimeter.
[2] Luckily, nothing serious enough to require surgery and I am gradually getting back out on the road and track.