Schrodinger's superconductor naturally stable in two states at once
Quantum computers have the potential to someday far outperform our traditional machines, thanks to their ability to store data on “qubits” that can exist in two states at once. That sounds good in theory, but in practice it’s hard to make materials that can do that and stay stable for long periods of time. Now, researchers from Johns Hopkins University have found a superconducting material that naturally stays in two states at once, which could be an important step towards quantum computers.
Our current computers are built on the binary system. That means they store and process information as binary “bits” – a series of ones and zeroes. This system has worked well for us for the better part of a century, but the general rate of computing progress has started to slow down in recent years.
Quantum computers could turn that trend on its head. The key is the use of qubits, which can store data as either a one, a zero or both at the same time – much like Schrödinger's famous thought experiment with the cat that's both alive and dead at the same time. Using that extra power, quantum computers would be able to outperform traditional ones at tasks involving huge amounts of data, such as AI, weather forecasting, and drug development.
The problem is, materials made for regular computers don’t work so well outside their comfort zone. So far, most progress towards practical quantum computers has been done using superconductors. In order to keep regular superconductors in a superposition of two states at once, a very precise, external magnetic field needs to be applied to each qubit individually. And with so many of them crammed in close quarters, that’s tricky to pull off without making electronics huge and bulky.
But now the team has found a material that can naturally hold a superposition without needing any external magnetic field. The material is called β-Bi2Pd, and when made into a ring shape, it becomes what’s known as a flux qubit. That means that electrical currents can flow both clockwise and counterclockwise at the same time.
"We've found that a certain superconducting material contains special properties that could be the building blocks for technology of the future," says Yufan Li, first author of the study. “A ring of β-Bi2Pd already exists in the ideal state and doesn't require any additional modifications to work. This could be a game changer.”
While the discovery is intriguing, the researchers say this is just one step towards practical quantum computers. There’s another missing component – hypothetical particles known as Majorana fermions, which are believed to be their own antiparticles. By encoding a pair of Majorana fermions which are separated within a material, it’s thought that they would be stable enough to prevent data being lost in a quantum computer.
The problem is, so far the properties of Majorana fermions have only been detected in "quasiparticles," which arise out of the movements of other particles but aren't themselves "real" particles. Think of them like bubbles in a drink – they are clearly observed and measured but are created through the interactions of other particles. Majorana fermions are yet to be discovered as particles themselves, but they're believed to be hiding out in a certain type of superconducting material. In their tests the researchers found that thin films of β-Bi2Pd are just the right type of material, meaning the next step is actually looking for the particles in the material.
"Ultimately, the goal is to find and then manipulate Majorana fermions, which is key to achieving fault-tolerant quantum computing for truly unleashing the power of quantum mechanics," says Li.
The research was published in the journal Science.
Source: Johns Hopkins University