Quantum computing in 2024: What are the challenges?

Fault tolerance

There have been a number of recent developments that point to improvements in error correction. These pave the way to quantum computing that could eventually be used to solve computationally challenging problems that cannot be realistically run on a classical computing architecture.

For instance, in January, QuEra Computing announced a strategic roadmap for a series of error-corrected quantum computers, starting in 2024 and culminating in a system with 100 logical error-corrected qubits in 2026. Quantum hardware developer Alice & Bob, in collaboration with the research institute Inria, has also unveiled a quantum error-correction architecture.

Building on previous research based on LDPC code, a class of efficient error correction codes that reduce hardware requirements to correct errors occurring in information transfer and storing, the theoretical research found that 100 high-fidelity logical qubits could be achieved using 1,500 physical “cat” qubits, designed to reduce so-called bit-flip errors in quantum computing.

The researchers cited previous calculations that showed the factorisation of RSA-2048 integers could be theoretically done in four days using 350,000 cat qubits. “We estimate that, under the same hardware assumptions, the improvements proposed in this paper would reduce this number to less than 100,000 cat qubits, and seven days of computation,” they said. 

Alice & Bob said the results indicate that the combination of cat qubits with classical LDPC codes produces a viable architecture for a large-scale quantum computer. The company said the architecture could be further improved by optimising protocols for implementing logical gates or by continuing to improve the design of cat qubits at the hardware level.

“Over 90% of quantum computing value depends on strong error correction, which is currently many years away from meaningful computations,” said Jean-François Bobier, partner and director at the Boston Consulting Group. “By improving correction by an order of magnitude, Alice & Bob’s combined innovations could deliver industry-relevant logical qubits on hardware technology that is mature today.”

The State of quantum report also highlighted cost as a potential barrier. The high cost of quantum computing time compared with other high-performance computing systems poses a barrier to widespread adoption, the report’s authors noted.

Jan Goetz, CEO and co-founder of IQM Quantum Computers, said: “2023 was a year of steady technological progress resulting in larger qubit counts and initial error correction, as companies successfully published and followed quantum roadmaps.

“However, the algorithmic side remains less predictable. While scaling processors is largely an engineering challenge, estimating timelines for software improvements is more dependent on hardware progress.”