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Cat Qubits Could Deliver Useful Quantum Computers Years Sooner Than Expected

PARIS, February 23, 2023 — Alice & Bob, a leading developer of quantum computing technology, today announces a significant finding from its latest research paper. The results, obtained in collaboration with the CEA (France’s Atomic Energy Commission), indicate that quantum computers using “cat qubits” of the kind Alice & Bob is developing, will be able to run Shor’s algorithm with as little as 300,000 qubits (quantum bits).

This number is 60 times smaller than the amount of qubits some other quantum computing technologies1 would require to perform the same task. Consequently, a useful quantum computer could be built years sooner than previously expected, using cat qubits.

“The hardware efficiency that Alice & Bob’s technology offers can help get us into the quantum era sooner than expected before,” said Theau Peronnin, CEO at Alice & Bob. “Reducing the number of qubits required to achieve this performance means that scaling these machines to a size where they are useful for a wide range of applications can happen sooner than expected.”

Building a quantum computer with enough qubits to reach this useful threshold is one of the main challenges the quantum industry is facing. Achieving a 60-fold decrease in qubit count therefore translates to a much shorter time to market for a useful quantum computer.

Today, Shor’s algorithm is broadly used as a benchmarking tool by many in the quantum industry. Because of the algorithm’s complexity, it is widely accepted that if a quantum computer can run Shor’s algorithm successfully on a reasonably large number, it will also be capable of running a vast range of other impactful quantum algorithms.

An example of one such application is deciphering the cryptographic keys of Bitcoin or other crypto currencies. The research paper thoroughly demonstrates how Bitcoin encryption could be broken in only 8 hours and with as little as 126,000 cat qubits, both far less than previously forecast2,3.

Nicolas Sangouard, researcher at CEA added “Our results highlight the benefit of using Alice and Bob’s platform and more broadly, of focusing on any platform exhibiting a noise bias to implement a large-scale quantum computer. This significantly reduces the number of qubits, by up to two orders of magnitude, to run large scale algorithms.”

Background on the research paper:

For those unfamiliar, quantum computers operate using qubits, which can be difficult to keep coherent (i.e., error-free) even for a short time. One of the primary roadblocks in the industry is scaling the number of qubits in a quantum system to a level where that system can deliver a quantum advantage to users, while maintaining coherence over such a large number of qubits. To ensure coherence, a large portion of the qubits in these systems are used up in “error- correction”. This imposes a sizable qubit hardware overhead because a significant portion of the qubits are used for something other than calculation.


[1] C. Gidney and M. Eker ̊a, “How to factor 2048 bit RSA integers in 8 hours using 20 million noisy qubits,” Quantum, vol. 5, p. 433, apr 2021. [Online]. Available: https://quantum- journal.org/papers/q-2021-04-15-433/
[2] M. Eker å and J. H ̊astad, “Quantum algorithms for computing short discrete logarithms and factoring rsa integers,” 2017. [Online]. Available: https://arxiv.org/abs/1702.00249
[3] D.Aggarwal, G. Brennen, T. Lee, M. Santha, and M. Tomamichel, “Quantum attacks on bitcoin, and how to protect against them,” Ledger, vol.3, oct 2018. [Online]. Available: https://doi.org/10.5195%2Fledger.2018.127

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