What in the World is a Qubit?

To many people, quantum computers are considered the holy grail of information technology. They would be able to solve problems and break secret codes using quantum mechanics— taking them a fraction of a second compared to the decades it would take modern technology. We don’t have these computers (yet), but we already have its smallest component, the qubit.

The qubit is a unit of information using quantum mechanics. It has some funky properties that give it an edge over classical bits. Qubits don’t just have the 0 and 1 of current computers: they use combinations of states involving the probability of getting 0 or 1. Instead of a simple “yes or no” answer, there are whole dimensions of the possibility of getting a yes or no answer.

Qubits are made from many different materials, such as photons, electrons, ions, even superconducting wires, or diamonds. The trick is to trap them (usually with a magnetic or electric field) in such a way that their desired quantum properties come to the fore, so that we can manipulate them to store information or do math. However, they don’t last in this position for very long, maybe a few milliseconds if we’re lucky.

There are two main ways for qubits to talk to one another: sending a particle encoded with information (like an electron or photon) from one qubit to another, or using entanglement. Entanglement is when qubits share such a strong connection that they will mirror each other over vast distances. You can even put some information in one qubit and it will pop up in the other automatically. Entangling qubits also exponentially increases their computing power. Yet, the more entanglements, the weaker the connections are. The current record is fourteen ions entangled together.

Scientists are still trying to figure out the path forward for quantum computing. The answer might be found in combining different types of qubits or a hybrid system of classic and quantum. Even without a quantum computer, they still have something else to show for their work on qubits: the quantum simulator, made by a team at the National Institute of Standards and Technology in Colorado. It consists of hundreds of beryllium ions that can be manipulated to mimic the quantum properties of any material, even ones we can’t measure in the real world.

Who knows, we might use the simulator to find something out about a material that can help get quantum computers rolling.

For more information on the crazy world of quantum mechanics, check out Spooky Action: The Drama of Quantum Mechanics on Saturday, June 2nd at 8PM at the NYU Skirball Center.

(Photo courtesy of Britton/NIST)