Our Bet in Quantum Computing
Quantum computing is one of the most ambitious challenges in science and engineering today. Achieving “useful” quantum computers, ones that solve real-world problems, requires years of innovation, problem-solving, and relentless work.
When Théau and I started Alice & Bob in 2020, quantum computing was already progressing rapidly. Big players like Google and IBM were making headlines with their advances. But we made, or some might say, we had to make, a different choice.
We placed our bet on cat qubits, an emerging technology at the time, but one that promised to provide the strong foundation needed for practical, fault-tolerant quantum computing in a more efficient way.
Of course, this depended on one thing: being able to control the cat.
Why Cat Qubits?
Cat qubits are complex, not only a technological challenge, but also a deep physics problem. The principles behind them are intricate, even by quantum standards. But the payoff is worth it: with the right control, cat qubits provide a pathway to efficient error correction at scale. By focusing on quality over quantity, we can avoid massive hardware setups.
A single, well-controlled cat qubit is a strong building block for fault-tolerant quantum computers that are both powerful and efficient.
This was our bet: if we could demonstrate that cats are indeed protected from a whole class of quantum errors, as theory predicts, we could use a shortcut to the finish line to win the race, despite starting later and smaller than other players.
The Journey So Far
Thanks to the collective efforts of the entire community, and especially our talented team at Alice & Bob and our close academic partners, cat qubits are no longer just a bet.
We’ve made tremendous progress, and much of it is now testable on the cloud. Our cat qubits can be reliably manufactured and controlled, and we are scaling up to 16 cat qubits now. On Boson 4, our single-qubit device, we set a world record for bit-flip protection, 7 minutes, far beyond the tens of millisecond of other superconducting quantum systems. Boson 4 was launched on Google Cloud for everyone to access and test earlier this year, marking an important product milestone.
Theoretical breakthroughs are equally exciting. For example, we’ve shown that a quantum computer using cat qubits could run Shor’s algorithm with up to 60 times fewer qubits than other approaches, and 200 times fewer when employing advanced error correction schemes. A few hundred thousand cat qubits could crack RSA encryption methods, whereas 20 million would be needed for competing architectures.
Looking back, our bet feels a bit less risky now.
Our Roadmap
With this solid foundation, the strategy gets clearer and we are able to share our roadmap to build a useful quantum computer by 2030. This roadmap outlines five key milestones that will bring us closer to achieving the first fault-tolerant quantum computer capable of solving real-world problems.
The Five Key Milestones
- Master the Cat Qubit
- Build a Logical Qubit
- Fault-Tolerant Quantum Computing
- Universal Quantum Computing
- Useful Quantum Computing
The Roadmap in Detail: From Theory to Practicality
The full roadmap (available for download) goes into the specifics of the technical milestones and challenges Alice & Bob is addressing. It explains step by step how each challenge we solve brings us closer to a practical, fault-tolerant quantum computer.
This roadmap provides a detailed, technical view of which cat qubit-based quantum processing units, the successors to our Boson chips, awaits us along the way.
Looking Ahead: Toward Practical Quantum Computing
As we continue to develop a useful quantum computer, our primary focus is on practicality. While the promise of quantum computing is widely recognized, the real challenge is making it achievable, in terms of cost, energy efficiency, footprint, and timelines, a problem that is not always talked enough about.
In this short blog post, I have mentioned several key concepts of quantum computing: qubits, quantum error correction, universality… However, for accurately understanding our strategy and, more broadly, for appreciating the real challenges facing the field, getting familiar with these concepts is essential.
This is why our roadmap was not published alone. It is the fourth and last section of our whitepaper, “THINK INSIDE THE BOX: QUANTUM COMPUTING WITH CAT QUBITS.” The whitepaper is designed to help anyone, regardless of their background, grasp the most crucial aspects of quantum computing, as well as understand the cat qubit and why hardware efficiency is so critical.
To make it even more accessible, the full whitepaper is available both in a fully illustrated, printable version and as an audiobook narrated by Christopher Bishop.
Conclusion
By focusing on hardware efficiency with cat qubits, we are reducing the resources needed to achieve quantum advantage and enhancing the impact of every new, scaled-up solution the superconducting qubit community delivers. These combined actions are necessary to make quantum computing viable for industries and society at large.
The current phase of our journey focuses on understanding cat qubit’s properties at scale and refining our approach to logical qubits and gates to achieve fault-tolerance and universality. By 2030, our goal is to deliver a quantum computer that solves real-world problems.
This is becoming less of distant vision. It is transforming into a practical, achievable goal, and we are moving toward it, one milestone at a time.
For a full deep-dive:
