IBM Corp. today debuted its newest and most sophisticated quantum processor, which features 127 qubits as well as several major architectural improvements over earlier chips.

The processor, dubbed Eagle, marks a new milestone in IBM’s efforts to develop large-scale quantum computers. Eagle is the first chip from the company to feature more than 100 qubits. According to IBM, Eagle’s high qubit count also makes it the first quantum processor that’s too advanced to be simulated on a classical supercomputer.

Quantum chips use quantum mechanical phenomena to perform certain computing operations faster than traditional computers. The technology is still at an early stage and currently doesn’t lend itself to many practical applications. However, it’s believed that future quantum computers with more qubits than today’s systems could take on calculations too complex for even the fastest classical supercomputers.

IBM has been steadily adding more qubits to its quantum processors in recent years to move closer towards unlocking the technology’s future applications. IBM’s early Canary quantum chips featured five qubits. They were followed by the 27-qubit Falcon series and the Hummingbird processor that debuted last year, which features 65 qubits.

Though IBM’s latest Eagle chip only made its debut today, the company is already working on future iterations of its quantum hardware. Eagle is set to be followed next year by Osprey, a processor that will have more than 400 qubits. In 2023, IBM intends to introduce an even more powerful processor expected to feature north of 1,000 qubits.

Building faster quantum chips is not as simple as adding more qubits to an existing design. To equip Eagle with 127 qubits, IBM’s researchers had to make several major architectural improvements.

Eagle is based on the so-called heavy hexagonal quantum chip design that IBM first detailed last year. The design was created with the goal of reducing qubit errors, which represent one of the biggest obstacles to large-scale quantum computing. 

In a quantum chip,  qubits work together to carry out calculations. The qubits are linked together with special connections to let them exchange information for processing purposes. Linking qubits is essential to facilitating computations, but also creates a challenge: Linked qubits interfere with each other, leading to errors that can render calculation results inaccurate.

The heavy hexagonal design that IBM implemented in Eagle reduces error rates. Eagle is designed such that each of the chip’s qubits is linked to several other neighboring qubits to facilitate joint computations. However, there are fewer links between neighboring qubits than in IBM’s previous quantum chip architectures. It’s this detail that helps reduce errors.

Because linked qubits interfere with one another, reducing the number of links reduces interference, which translates to fewer calculation errors. At the same time, qubits in Eagle still retain the ability to exchange data. 

“Eagle is based upon our heavy-hexagonal qubit layout as debuted with our Falcon processor, where qubits connect with either two or three neighbors as if sitting upon the edges and corners of tessellated hexagons,” IBM executives Jerry Chow, Oliver Dial and Jay Gambetta detailed in a blog post today. “This particular connectivity decreased the potential for errors caused by interactions between neighboring qubits — providing significant boosts in yielding functional processors.”

Another innovation in Eagle is a technology called readout multiplexing. In IBM’s previous-generation quantum processors, every qubit was deployed with a dedicated set of electronic components responsible for writing data to the qubit and reading the results of calculations. The readout multiplexing technology in Eagle reduces the amount of electronics necessary to read and write data, IBM said.

The quantum mechanical phenomena that qubits use to carry out calculations only emerge if the chip in which they reside is cooled to temperatures near absolute zero. As a result, Eagle and  IBM’s other quantum chips run not in standard servers but rather inside a powerful industrial fridge.

The fridge that houses a quantum chip forms part of a larger chassis that also includes various other auxiliary components. The quantum chip, the fridge and the various auxiliary components included in the chassis together form a quantum computer. 

Alongside Eagle, IBM today previewed the next iteration of its quantum computer design, the IBM Quantum System Two. The company said that the design will be capable of housing not only Eagle but also the chip with more than 1,000 qubit it plans to launch in 2023. Moreover, IBM Quantum System Two will make it possible to combine multiple quantum chips together.

IBM plans to make room in the chassis for multiple quantum chips by optimizing the space efficiency of the cryogenic components used to cool the system. The company is pursuing the effort in collaboration with Bluefors Oy, a Finland-based firm that makes refrigeration equipment for quantum computers.

IBM’s quantum chips are based on superconducting qubit technology. The chips represent data in the electronic quantum states of artificial atoms. IBM applies sequences of microwave pulses to the artificial atoms in order to carry out calculations. The company has been researching the technology since the mid-2000s and made its first quantum computer available via the cloud in 2016.

Photo: IBM