A cat qubit encodes quantum information in a superposition of two coherent states (classical-like oscillation patterns) of a microwave resonator, inspired by the thought experiment of Schrodinger's cat being simultaneously alive and dead. The logical |0⟩ and |1⟩ states correspond to coherent states with opposite phases (|+α⟩ and |−α⟩), where α characterizes the amplitude of the oscillation. Amazon Web Services (through its Ocelot chip, announced in 2025) and Alice & Bob are the primary developers of cat qubit technology.
The key innovation of cat qubits is their built-in asymmetric error protection. Bit-flip errors (|0⟩ ↔ |1⟩ transitions) require the system to tunnel through a large energy barrier in phase space, making them exponentially suppressed as the coherent state amplitude α increases. This means cat qubits naturally resist bit-flip errors without any active correction, reducing the error correction problem to handling only phase-flip errors. This asymmetry dramatically reduces the overhead for full quantum error correction — instead of needing a 2D surface code that corrects both error types, cat qubits need only a 1D repetition code for the remaining phase-flip errors.
Amazon's Ocelot chip demonstrated this principle in early 2025, showing that bit-flip error rates decreased exponentially with cat state size while maintaining manageable phase-flip rates. The company claimed this architecture could reduce the qubit overhead for fault-tolerant quantum computing by up to 90% compared to conventional approaches. However, cat qubits require sophisticated nonlinear dissipation engineering to stabilize the cat states, and the technology is still in early stages compared to transmon-based processors in terms of qubit count and system integration.