IBM updates path to fault-tolerant quantum computing

IBM has updated its roadmap for building large-scale, fault-tolerant quantum computers, setting the stage for practical and scalable quantum computing.

A quantum computer of this kind, with hundreds or thousands of logical qubits, could run hundreds of millions to billions of operations, which could accelerate time and cost efficiencies in fields such as drug development, materials discovery, chemistry and optimisation.

However, the success of executing an efficient fault-tolerant architecture is dependent on the choice of its error-correcting code, and how the system is designed and built to enable this code to scale. Error-correcting codes needed for more powerful quantum computers require an unfeasible number of physical qubits, which provide enough logical qubits to perform complex operations.

According to IBM, scaling error-correcting code also means the amount of infrastructure and control electronics needed is impractical beyond small-scale experiments and devices. 

IBM has set its sights on a new approach to quantum error correction using low-density parity-check (LDPC) codes in a modular approach to quantum computing known as bicycle architecture. 

“IBM is charting the next frontier in quantum computing,” said Arvind Krishna, chairman and CEO at IBM. “Our expertise across mathematics, physics and engineering is paving the way for a large-scale, fault-tolerant quantum computer – one that will solve real-world challenges and unlock immense possibilities for business.”

IBM’s goal is to build a machine that exhibits sufficient fault tolerance to suppress enough errors for useful algorithms to succeed. The machine also needs to be able to prepare and measure logical qubits through computation in real time and offer a modular scale to hundreds or thousands of logical qubits to run more complex algorithms.

The company has published two academic papers outlining its approach to building a scalable, error-tolerant quantum computing architecture. The first covers high-rate quantum error correcting codes based on using moderate overhead in control logic and the number of physical qubits needed for fault-tolerant quantum computing. The second paper discusses an approach to quantum error correction using real-time heuristic decoding, which is run on field programmable gate array chips.

“When taken together, these papers will demonstrate the essential criteria for a large-scale error correction approach,” said Matthias Steffen, head of quantum processor technology at IBM Quantum.

Jay Gambetta, vice-president, IBM Quantum, said: “We’ve cracked the code to quantum error correction and it’s our plan to build the first large-scale, fault-tolerant quantum computer.”

Gambetta admitted that IBM has a lot of work to do to convert these concepts into working quantum computing hardware, but they pave the way to its next generation of quantum computer, the Quantum Starling. This is set to be ready by 2029 and perform 20,000 times more operations than today’s quantum computers.

The Quantum Starling, which will be built in the IBM Quantum Data Center in Poughkeepsie, New York, lays the foundations for the company’s direction of travel towards a large-scale system, Blue Jay, which is earmarked for delivery in 2033. According to IBM, Blue Jay will be capable of performing a billion circuit operations using 2,000 logical qubits, allowing it to tackle complex computations.