You have probably heard about the ‘weirdness’ of quantum mechanics. It’s hard to come by a piece of writing on the subject that doesn’t quote a famous physicist lamenting the incomprehensibility of quantum behaviour. But as Conor Feehly discovers, there are new ways to get a quantum of intuition.
Yes, quantum physics, at least initially, can feel counterintuitive. Quantum mechanical systems appear to obey a different set of rules compared to the systems we encounter on a daily basis in our macroscopic world. And yet, over time, quantum scientists have been able to intimately acquaint themselves with the concepts and mathematics that underpin the quantum world. Scientists who work in this area on a daily basis can come to see events through a quantum lens. This strange space of ideas can become second nature as they develop an intuition for what was once alien.
“I feel like we are ready to move on from the way quantum mechanics has been portrayed,” says Nicole Yunger Halpern, who studies quantum information theory and quantum thermodynamics at the National Institute of Standards and Technology in Maryland. Yunger Halpern is also the most frequent contributor to the blog Quantum Frontiers, which communicates the science of quantum mechanics for the Institute of Quantum Information and Matter at Caltech.
The effort to demystify the quantum world also has a new tool – gaming. Over the last few years, quantum educators have been integrating features of quantum behaviour into a variety of video games, with the hope that introducing this world to younger and younger people, they might be able to build intuitive quantum mechanical knowledge in the next generation of scientists.
“If I had come across these games when I was 8, 10 or 12 years old, how could that have influenced me?” asks Carrie Weidner, a quantum engineer at the University of Bristol. Weidner spent three years developing quantum games and other educational outreach tools at Aarhus University in Denmark.
Human intuition, whether we are willing to admit it or not, is a central component in the story of science. It empowers scientists to visualise, to predict, to ask interesting questions and devise ways to answer them. Scientists intuit their way towards progress by telling stories about the quantum world, checking how far their guesses stray from the truth, and correcting their stories with experimentation and math. In a broader sense, the intuition that quantum scientists possess demonstrates the remarkable plasticity of the human mind, and its ability to wire itself to concepts that defy our everyday experience.
‘Intuitive physics’
From the first day you enter the world, you are exposed to an environment that has certain regularities. Things fall down. Objects don’t pass through one another. Items persist. These regularities help us form subconscious rules for how objects interact and events unfold in the world around us. Developmental psychologists call this our ‘intuitive physics’.
“Infants are born with a skeletal framework of abstract physical principles and concepts,” says Renee Baillargeon, a developmental psychologist who studies physical reasoning in infants at the University of Illinois. “These guide how infants reason about physical events and form expectations about their outcomes.”
If, for instance, you were to hide a cup behind a screen, which you then lowered to reveal no cup, infants as young as 2 or 3 months old will be surprised. Their expectation of how the event should unfold involves the concept of persistence (all other things being equal, objects persist, as they are, in time and space) – objects don’t just spontaneously disappear, right?
“Infants form event categories, such as occlusion, containment, support, collision and so on, which correspond to the types of events they see in their daily lives,” Baillargeon explains. “As they interact with their physical environment, infants learn, one by one, the features that are important for each event category.”
All of this means that when we run into events or concepts that seem to violate the intuitive physics we emerged with at infancy and developed through childhood, we are likely to see it as something counterintuitive – mystical, perhaps – or just downright weird. Quantum mechanics, of course, is full of such violations.
Going back to the cup from earlier, even infants have object permanence. They understand that even if they can’t see an object, it continues to exist. However, one feature of quantum systems is fluctuation. This refers to random changes in the properties of particles and of space itself. To explain this variability, physicists often invoke particles popping into and out of existence. Not so permanent, then?
Objects also don’t tend to pass through impenetrable barriers in our scaled-up reality. “How many throws does it take for a ball to pass through a concrete wall?’ Weidner rhetorically asks. Another bizarre feature of the quantum world, called ‘quantum tunneling’ describes that, by chance, subatomic particles will sometimes find themselves on the other side of an energetic or structural blockade. So does this mean objects can pass through one another…?
“The fact that I can sit here (in my lab) and talk about what is happening to an atom like, well it is probably tunneling. That statement is so anathema to everything I was exposed to for the first 18, 20 years of my life. It’s akin to me saying, here hand me that grand piano,’’ explains Weidner.
Locality also plays an important role in our intuitive physics, where we expect objects to interact with one another only if they are close in time and space. And yet, quantum entanglement allows for two particles to be linked across vast distances, a connection Einstein referred to as ‘spooky action at a distance’.
“When you learn classical physics, it’s relatively easy to see what’s going on,” Weidner adds. “You drop something and it falls. With quantum behaviour, the hard bit is that there is nothing here that I have on my desk that I could show you and say ok, here’s how we can demonstrate quantum mechanics … so there is this mystique.”
Science and intuition
In science, intuition could be considered a bit of a dirty word. Scientists do experiments. They go where the data tells them. Nowhere is there room for something as ‘woo woo’ as feelings or intuition. This view, however, mischaracterises intuition – turning it into something mystical, rather than a subconscious skill that is developed through time and understanding. Just as our ‘intuitive’ physics, in large part, is formed through interacting with the world as an infant and child, scientists are capable of developing intuitive knowledge in the abstract, arcane corners of science that they spend their days toiling in. “A colleague told me she finds quantum physics more intuitive than classical physics, because she has been working on it for so long,” says Yunger Halpern.
The history of science has also been a process of breaking down what we think we know about the world, and building up something new. Even if new ideas initially felt unintuitive, say, that Earth wasn’t the centre of the universe (thanks Copernicus), or that time was actually relative (thanks Einstein), it didn’t stop the next generation of scientists incorporating that ‘counterintuitive’ knowledge into their model of the world. And crucially, it didn’t stop them building on it.
“If we didn’t have intuition, we probably couldn’t do much research at all. We need some sense of where we are going, where we expect to get, how we might get there, and there is plenty of opportunity for finding out that we are wrong, so we can readjust our path,” says Yunger Halpern.
Yunger Halpern has also been working to develop a visual aesthetic through sculpture for a specific area of her research – quantum thermodynamics. Thermodynamics is the science of energy, heat and work. It was developed during the 1800s and was inspired by the industrial revolution. Steam engines were powering factories, and people naturally wanted to understand how efficiently the engines could operate. But these thermodynamic concepts – heat, work, temperature – are also relevant to small, quantum systems. It’s the meeting of old and new, the past and the future – quantum steampunk.
“This sculpture is meant to be a quantum engine. The idea is to engage viewers in quantum thermodynamics and quantum physics, especially viewers who don’t think of themselves as science people, but think of themselves as art-type people. Hopefully they will be drawn into the sculpture. Then they can scan a QR code and learn more about its scientific elements,” explains Yunger Halpern. “A decent part of theoretical physics involves aesthetics and I find it really interesting that quantum thermodynamics has an aesthetic. Aesthetics are, in a way, part of intuition.”
Quantum games
The seeming weirdness of the quantum world might not last. That’s because individuals and organisations have been working on ways to introduce quantum concepts to younger people in new, engaging ways. Back in 2013, Caltech’s Institute for Quantum Information and Matter partnered with Google to produce Qcraft. This variation of the game Minecraft incorporates quantum behaviours into gameplay. In 2017, Chris Cantwell developed quantum chess at Quantum Realm Games in California, which even had some international tournaments.
Quantum researchers like Jacob Sherson at Aarhus University have also been developing quantum games and novel approaches to educational outreach. Weidner spent 3 years working with Sherson on quantum games and games for education in general in the quantum physics sphere during a postdoc at Aarhus. “This idea is that through a combination of educational tools, and solving puzzles, you can develop an intuition for these concepts. The difference between me and my students is that I have had time with these ideas…and so any tool that is going to ease that transition, whether you start at age 12, 18 or 30, is going to be a massive help,” says Weidner.
Everybody enters the world a scientist. Play is really just an infant’s way of doing experimentation. Through play, children develop their intuitive physics for how things in the world behave and interact – so why not create a space for play in the quantum world?
“Exposure and getting it wrong is a big part of it. If you can hand someone a game and say ‘play with it’, whether it’s a virtual lab or quantum chess, people will learn how things work; by playing it, you build up that intuition. And then if you are interested, you can take it further,” Weidner explains.
Limits to intuition
Labelling quantum behaviour as counterintuitive disregards the capacity of the human mind to wire itself to new ideas and concepts through exposure. “It’s crazy what you can get used to,” says Weidner. Yes, features like entanglement and tunneling might be strange at first. But undoubtedly, quantum scientists have developed an intuition that allows them to play with these ideas, to challenge them with experiments that could lead to new insight or apply them to problems that nobody considered.
Quantum intuition in scientists speaks to a broader ability in humans to work with ideas that by all rights, we have no reason to be so competent with. We evolved to solve problems at the scale of reality that we can perceive. The once secret quantum world, orders of magnitude smaller than anything we can access with our senses, is now comprehensible to us in a meaningful way.
“Our skeletal framework does not bind us to a particular physical reality. We can enjoy sci-fi movies and Harry Potter movies that violate many basic physical assumptions … We can appreciate other physical realities, but revert to our own when it’s time to make a salad or fold laundry or rake the leaves or drive the children to school,” says Baillargeon.
What hidden layers of reality will we have to learn to intuit next?
Conor Feehly is a science writer based in New Zealand