US firm beats Microsoft, Harvard with 50 entangled logical qubits in quantum computer

Colorado-based Quantinuum has set a new record in quantum computing by successfully entangling 50 logical qubits.

The company’s Director of Computational Theory and Design, David Hayes, revealed this achievement at a plenary session of the Q2B conference held at Silicon Valley earlier this week.

The race to build quantum computers that will replace the fastest supercomputers of the day is heating up, and companies are pumping billions of dollars to reach their first. But for quantum computers to be deployed in the real world, we must first apply error corrections to their computations.

All computers are prone to errors in their computations. With silicon-based computers, we have developed error correction strategies that perform the job well. However, the nature of quantum computers makes replicating these correction approaches to quantum computers impossible, and new approaches need to be developed.

In addition to the quantum bits or qubits, researchers are interested in developing logical qubits to advance quantum computing.

Why logical qubits?

Logical qubits are groups of physical qubits that run quantum computations using specifications of a quantum algorithm. Researchers are deploying logical qubits to reduce error rates in quantum computations. Since different technologies are used for qubits, building and using logical qubits have varied approaches, too.

Earlier this year, Google’s quantum computing division demonstrated a method that can make a single logical qubit which is large and becomes more error-proof as its size increases. The other approach involves using a smaller number of qubits to make a larger number of logical qubits, providing a better check on error correction.

When more logical qubits are deployed, entangling them is crucial to get a coherent output, and this is where Quantinuum made a major leap.

Entangling logical qubits

Last month, Microsoft and Atom Computing set a record demonstrating the entanglement of 24 logical qubits. With the recent announcement of entangling 50 logical qubits, Quantinuum has more than doubled that number and broken two records in the process.

The first is for the largest number of entangled logical qubits, putting a fair distance between their achievement and Atom Computing. The second and more important one is setting up a computer with the largest number of logical qubits to date.

Interesting Engineering has previously reported how companies are building computers with 1,000 qubits and even more. However, a large number of qubits is irrelevant if its output cannot be error-corrected, and this is where the number of logical qubits is important.

Another QuEra Computing, along with Harvard University, had set this record with 48 logical qubits in 2023, and Quantinuum has marginally beat this record. Quantinuum’s Hayes was also quick to point out that the large number of logical qubits in their setup could only detect errors and not correct them.

So, although the company has set a record, the achievement will not necessarily turn into a fault-tolerant quantum computer anytime soon. Instead, it is now poised at an intermediate level step where it can detect the errors but isn’t correcting them.

According to Hayes presentation, the company’s achievement only provides one of the three high-level requirements for industrial-scale quantum computers. Quantinuum is developing capable hardware for quantum computers. Robust software that can control and optimize quantum computer performance and co-develop hardware and software to meet specific application needs are the other pieces of the puzzle that still need to be solved before a quantum computer becomes a reality.