The Cat Qubit in Plain English

Introduction

Quantum computing is a paradigm shift in computational technology, addressing problems that are intractable for classical computers. The development of a fault-tolerant quantum computer could accelerate both applied research and scientific discovery. However, practical quantum error correction remains a challenge.

Several error correction approaches have been proposed, and recent experiments show encouraging results. In 2024, Google Quantum AI presented the first logical qubit with error correction¹, while other research groups achieved similar milestones^2,3,4. However, these approaches require an impractical amount of hardware resources to achieve useful quantum computing.



The Cat Qubit

An alternative approach to quantum error correction lies in the design of the qubits themselves, aiming to incorporate intrinsic protection against certain types of quantum errors.

Dissipative cat qubits are designed to protect against bit-flip errors by default. Cats can be configured to exponentially suppress bit-flip errors⁵. This phenomenon, the “noise bias,” allows for more hardware-efficient error correction codes. Such efficiency can drastically reduce the number of qubits required to achieve fault tolerance, making useful quantum computers more feasible^6,7,8.

In this presentation, we will provide an intuition of both the physics and engineering behind the cat qubit. We'll explain how its unique design achieves noise bias and highlight some recent research advancements.