Quantum computers can get pretty complicated, so here’s some basic information to know.
How do quantum computers differ from classical computers?
Quantum computers work a lot like classical computers. The ones and zeros we think of in computing are based on the idea that silicon chips have transistors on them, which are tiny switches that can be controlled to let electrical current through them or not. As the book Quantum Computing for the Quantum Curious explains, “computer hardware understands the 1-bit as an electrical current flowing through a wire (in a transistor) while the 0-bit is the absence of an electrical current in a wire. These electrical signals can be thought of as “on” (the 1-bit) or “off” (the 0-bit).” Quantum computers, on the other hand, by using quantum bits (qubits), can process information differently. A classical bit has a value of either 0 or 1, whereas a qubit can have a value of 0, 1, or a superposition of the two—an in-between state that allows it to be both at the same time. In theory, this property would allow the computer to try multiple possible solutions to a problem to find the answer, instead of trying only one solution at a time. Caltech explains in a post that in addition to superposition, qubits can also be “entangled, meaning that they are linked quantum mechanically to each other. Superposition and entanglement give quantum computers capabilities unknown to classical computing.” Entanglement allows quantum computers to process more information, and it could also increase the security of networks. In 2019, this technology reached a notable milestone in a proof of principle task, completing a specific calculation Google assigned it eons faster than a supercomputer (specifically, it finished a task that would’ve taken a traditional supercomputer over 10,000 years in 200 seconds). According to Caltech, engineers can make qubits by manipulating atoms, subatomic particles, photons, or by creating “artificial atoms.” Currently, quantum computers rarely exceed 100 qubits. Here’s what they can actually look like. To maintain a quantum state, qubits have to sit inside nested chambers that are chilled to near absolute zero temperature and shielded from interactions with other molecules or disturbances from outside magnetic fields, Caltech wrote. And as you increase the number of qubits, they become harder to manage and isolate, meaning they’re more likely to collapse and lose their properties of superposition and entanglement. Researchers also want to figure out a hardware-based computer architecture that can correct quantum errors. One possible design is based on “Schrödinger-cat qubits,” which can stabilize qubits by preventing them from randomly flipping out of superposition into one of the binary states. “Classical computers have billions and even trillions of bits,” Fernando Brandão, a professor of theoretical physics at Caltech and head of quantum algorithms at AWS, said in a news release. “And that’s where we eventually would want to be with qubits.”
