Your laptop already runs on quantum physics, even if it doesn’t feel like it. The tiny transistors that switch your computer on and off only work because electrons behave like both waves and particles. But this year’s Nobel-winning physics research zooms in on something that looks even more ordinary: simple electrical circuits that, when cooled almost to absolute zero, stop behaving like everyday electronics and start acting like atoms.
How it works
In these experiments, researchers built tiny loops of superconducting metal separated by a microscopic gap called a Josephson junction. At room temperature, this would just be a quirky piece of hardware. But when the material is cooled to just a few thousandths of a degree above absolute zero, it enters a very different world. The metal becomes superconducting, meaning current can flow through it with no resistance. Random thermal motion gets frozen out. And under those conditions, the circuit begins to follow quantum rules instead of the usual rules of classical physics.
The basic setup sounds simple: send a small current through the circuit and watch the voltage across it. As long as the circuit sits in a special quantum state, the voltage stays at exactly zero. Eventually, that state “escapes,” and the voltage suddenly jumps to a higher value. By measuring how long the circuit stays in that zero-voltage state, and how that time changes when the device is nudged with microwaves of different frequencies, physicists can peer into what’s happening at the quantum level. In practice, this is extremely hard. The system is so sensitive that stray heat, vibrations, or electromagnetic noise can drown out the signal, so everything has to be tightly controlled and measured over and over again.
What they discovered
One of the strangest effects they’ve observed is quantum tunneling. Imagine a ball sitting in a valley, separated from the next valley by a hill. In classical physics, the only way to get the ball to the other side is to give it enough energy to roll over the hill. If you don’t, the ball stays put. In quantum mechanics, though, the “ball” is also a wave. There’s a small chance it will simply appear in the next valley without ever going over the top of the hill. Instead, it has tunneled through the hill. In these circuits, the “ball” is the state of the superconducting loop. The circuit’s energy landscape has valleys and hills set by its design. At the ultra-low temperatures of the experiment, the system doesn’t have enough ordinary energy to climb the hill, yet the state still occasionally “escapes” in exactly the way quantum tunneling predicts. That’s a strong sign that a device made of billions of individual atoms is behaving like a single quantum object.
The other key observation is that the circuit’s energy is quantised. In everyday life, we tend to think of energy as a ramp where you can stand anywhere along it. Quantum systems, like atoms, have energy levels more like a staircase: you can stand on one step or another, but not in between. To test if the circuit's energy had been quantised, the experimenters shone microwaves of different frequencies at the circuit while it sat in the zero-voltage state. The device only absorbed energy when the microwaves exactly matched the gap between two allowed levels, causing it to jump from one level to another. By scanning those frequencies, researchers could see that only specific jumps were possible. The energy of the circuit was locked into discrete levels, just like an atom.
Why it matters
Put tunneling and discrete energy levels together, and you get the central idea of this research: these are “artificial atoms.” They may look like weird little loops of wire on a chip, but they follow the same quantum rules that govern electrons in hydrogen or electrons in a semiconductor. The advantage is that artificial atoms can be engineered. We can choose their size, their shape, how strongly they interact with microwaves, and how easily they connect to other circuits. Instead of working with whatever nature gives us, we can design quantum systems on demand.
That’s why this work shows up everywhere in quantum technology. Many of today’s prototype quantum computers are built from circuits very similar to the ones in these experiments. Each circuit serves as a quantum bit, or qubit, that can encode information not just as a zero or a one, but as a superposition of both. Related devices are being developed as ultra-sensitive quantum sensors that could detect tiny magnetic fields, subtle changes in gravity, or faint electrical signals in the brain. The same principles could power parts of future quantum communication networks, where information is exchanged in ways that are much harder to hack or intercept.
This research is exciting, but it’s important to be honest about where things stand. These devices are still fragile and picky. They require extremely low temperatures, careful shielding, and elaborate error-correction schemes to keep their quantum properties from fading away. We are nowhere near a universal quantum computer on your desk. But the basic message of this work is already clear: quantum behavior doesn’t just belong to the invisible world of atoms and particles. Under the right conditions, the circuits we design and build can switch over to quantum rules, too.
Looking ahead
If you want a historical analogy, think about the first transistors in the 1940s. To most people at the time, they looked like obscure lab curiosities. No one holding one could have predicted smartphones or cloud computing. In the same way, these chilled circuits may look small and specialized today, but they are proof that we can engineer quantum behavior at will. The small shift, from “quantum is what nature gives us” to “quantum is something we can design,” is what makes this work feel like the starting point of an entirely new kind of technology.
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