What is Quantum Computing?

To talk about NC State’s quantum research and innovation, it is important to understand the fundamental principles that underlie quantum computing. Quantum computers aren’t just the next step in classical computing. They function by rewriting the rules of computing entirely.

North Carolina State University has rapidly become a hotspot for all things quantum innovation. NC State is host to an IBM Quantum Innovation Center, a groundbreaking hub for quantum computing education, research, development and application. University faculty – from the Departments of Electrical and Computer Engineering, Materials Science and Engineering, Physics and Astronomy, Computer Science and more – have come together to research and develop new methods, materials and devices in this emerging field. 

But first, perspective. To talk about NC State’s quantum research and innovation, it is important to understand the fundamental principles that underlie quantum computing. Quantum computers aren’t just the next step in classical computing. They function by rewriting the rules of computing entirely.

Department of Electrical and Computer Engineering Professor Daryoosh Vashaee, member of the ASSIST Center and director of the Nanoscience and Quantum Engineering Research Laboratory, helps break it down.

A quantum computer is to a classical computer what a classical computer is to an abacus. Essentially, it is a massive leap forward in computing technology that is so different from its predecessors, it is virtually unrecognizable. 

Qubits

“In a computer, every bit could be either 0 or 1. That’s a classical bit,” said Vashaee. “In quantum computers, we put this aside, and we say each quantum bit can exist as an infinite combination of 0 and 1. So instead of just 0 or 1, you have infinitely possible states that it can take. So, quantum computing is fundamentally different.”

Quantum computers use qubits, or quantum bits. Unlike regular bits, qubits can be a 0, a 1 or both at the same time. This is possible through a quantum property called superposition: where a qubit can exist in multiple states at once until it is ‘resolved’ or observed. Qubits don’t function in a yes/no paradigm. They can inhabit all states at once.

Think of Schrödinger’s cat, the most famous thought experiment concerning quantum superposition: the cat can be considered both alive and dead while it is inside the box, unobserved. This ability to handle multiple states at once is what lets quantum computers tackle highly complicated problems faster than classical machines.

Entanglement

“Entanglement is the other key ingredient when it comes to quantum computing,” said Vashaee. “When qubits become entangled, they stop behaving like independent coins you can flip separately. They start acting more like a single, shared system – even if they’re separated by distance. Measure one entangled qubit and you instantly learn something about the other, not because any signal raced between them, but because the information is stored in their relationship.”

Einstein famously called this, “spooky action at a distance”. It can look like teleportation, though nothing physical is beamed from one place to another. 

“In practice, entanglement is what lets quantum computers coordinate many qubits at once, linking their outcomes so the machine can represent patterns and correlations that would take a classical computer an enormous amount of time to track,” said Vashaee.

These fundamental principles set the foundation for quantum computing, and help explain why this emerging field has such vast potential, especially for tasks that are considered impossible to solve with classical computing. Quantum computers could one day accurately simulate complex chemical reactions, optimize large-scale logistical networks or model climate systems in ways beyond the reach of current technology.

“In quantum computers, everything is done in parallel, which significantly reduces computational time,” said Vashaee. “The dramatic improvements in computational capacity with quantum computing… there is just no way to compare it with classical computers.”