Cat Qubits and Alice & Bob Explained: Bosonic Qubits in Plain English

Updated 2026-10-11 | 4 min read | QUANTUM (QNT) community

Two kinds of qubit error

A qubit can go wrong in two main ways. A bit flip swaps 0 and 1. A phase flip scrambles the relationship between the two states (see superposition explained). Ordinary qubits suffer both, and fixing both at once is expensive. Codes like the surface code handle both types using many physical qubits per logical qubit. If you could make one error type nearly disappear in hardware, the software would only need to fix the other one.

What a cat qubit is

Instead of a single small circuit, a cat qubit uses a superconducting microwave resonator, a bit like a tiny electrical bell that can hold some number of energy packets (photons). The two logical states are two "coherent" states of the resonator, which are like two distinct, stable wave patterns. The name comes from Schrodinger's cat: the quantum information lives in a superposition of the two patterns. Bosonic is the general word for qubits stored in oscillators like this, as opposed to the two-level atom-like circuits in most superconducting chips.

The trick is active stabilization. A special driven circuit constantly pumps the resonator so that photons are added and removed in pairs. That pushes the resonator back toward the two allowed patterns and makes it very hard for noise to flip one into the other. Alice & Bob describes this as turning error correction from a two-dimensional problem into a one-dimensional one, which lowers the resources needed. It is a trade: bit flips become exponentially rarer as you use a larger average photon number, while phase flips get somewhat more likely, and those are then corrected with a simple repetition style code.

What Alice & Bob has reported

• 2024: The company reported that its Boson chip series produced a reproducible cat qubit, with a bit-flip time reported above seven minutes (about 430 seconds), which it called a record for superconducting qubits.
• September 25, 2025: The company announced preliminary results on bit-flip times of roughly an hour (about 41 flips observed over 61 hours, according to a secondary write-up). The stated measurement was a bit-flip time between 33 and 60 minutes (95% confidence) at a mean photon number of 11, and a Z gate with 94.2% fidelity in 26.5 nanoseconds. The next step it named was testing performance under a two-qubit CNOT gate. Compare this with about 25 milliseconds reported for other leading superconducting qubits.

Bit-flip protection alone is not a complete computer. Gates between cat qubits, and keeping them while stabilizing, are the hard part, which is why the company calls the 2025 numbers preliminary. These numbers are company reported and, as far as I could verify, were announced via press release and blog post rather than an independent paper.

The roadmap

Alice & Bob has laid out five milestones, each linked to a named chip series: master the cat qubit (Boson series, reported complete in 2024); build a logical qubit below the error correction threshold (Helium series, in development); fault-tolerant systems with multiple logical qubits and a first logical gate (Lithium series); universal quantum computing with magic state factories (Beryllium series); and finally practical quantum advantage with 100 high-fidelity logical qubits (Graphene series). The company's stated aim is a fault-tolerant machine by 2030. In January 2025 it announced a 100 million euro Series B round, reported by TechCrunch as 104 million dollars, which it says will fund performance work and new lab and production capacity.

Why this could matter

Fewer physical qubits per logical qubit means smaller, cheaper machines. If cat qubits deliver, they could shorten the path to useful error-corrected computing. Other firms also explore bosonic ideas, and OQC takes a different route of flagging errors, covered in the OQC guide. Google and IBM chase the conventional approach (see error correction in 2026).

Honest limits

The roadmap is a company plan. Skipping the hard milestones (logical gates, many cats working together) would break the cost advantage. No one has yet shown a large fault-tolerant machine of any kind. Still, a bit-flip time stretching from milliseconds toward minutes is a striking sign that clever qubit design can change the game. This is educational content, not financial advice, and the QNT memecoin has no connection to Alice & Bob.

Sources and further reading

• R&D World: Alice & Bob outlines roadmap to 100 logical qubits by 2030
• The Quantum Insider: Alice & Bob preliminary bit-flip time results (September 2025)
• TechCrunch: Alice & Bob raises 104 million dollars (January 2025)

Reported as of 2026-10-09. Company roadmaps are targets and often slip. Check each company's own announcements. Nothing here is financial advice, and the QNT memecoin is independent of Quantinuum Ltd and of every company named.

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