{"id":6532,"date":"2025-04-10T01:21:14","date_gmt":"2025-04-10T01:21:14","guid":{"rendered":"https:\/\/www.europesays.com\/uk\/6532\/"},"modified":"2025-04-10T01:21:14","modified_gmt":"2025-04-10T01:21:14","slug":"quantum-computing-companies-focus-on-modular-set-ups","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/uk\/6532\/","title":{"rendered":"Quantum Computing Companies Focus on Modular Set Ups"},"content":{"rendered":"

Quantum-computing companies have been competing for years to squeeze the most qubits<\/a> onto a chip. But fabrication and connectivity challenges mean there are limits to this strategy. The focus is now shifting to linking multiple quantum processors<\/a> together to build computers large enough to tackle real-world problems.<\/p>\n

In January, the Canadian quantum-computing company Xanadu<\/a> unveiled what it says is the first modular quantum computer. Xanadu\u2019s approach uses photons as qubits\u2014just one of many ways to create the quantum-computing equivalent of a classical bit. In a paper published that same month<\/a> in Nature, researchers at the company outlined how they connected 35 photonic chips<\/a> and 13 kilometers of optical fiber<\/a> across four server racks to create a 12-qubit quantum computer called Aurora. Although there are quantum computers<\/a> with many more qubits today, Xanadusays the design demonstrates all the key components for a modular architecture that could be scaled up to millions of qubits.<\/p>\n

Xanadu isn\u2019t the only company focused on modularity these days. Both IBM<\/a> and IonQ have started work on linking their quantum processors<\/a>, with IBM hoping to demonstrate a modular setup<\/a> later this year. And several startups<\/a> are carving out a niche building the supporting technologies<\/a> required for this transition.<\/p>\n

Most companies have long acknowledged that modularity is key to scaling, says Xanadu CEO Christian Weedbrook, but so far they have prioritized developing the core qubit technology, which was widely seen as the bigger technical challenge.Now that chips with practical use are in sight and the largest processors<\/a> feature more than 1,000 qubits<\/a>, he believes the focus is shifting.<\/p>\n

\u201cTo get to a million qubits, which is when you can start truly solving customer problems, you\u2019re not going to be able to have them all on a single chip,\u201d Weedbrook says. \u201cThe only way to really scale up is through this modular networking approach.\u201d<\/p>\n

Xanadu has taken an unorthodox approach by focusing on the scalability problem first. One of the biggest advantages of relying on photonics<\/a> for quantum computing\u2014as opposed to the superconducting qubits<\/a> used by IBM and Google\u2014is that the machines are compatible with conventional networking technology, which simplifies connectivity.<\/p>\n

However, Aurora isn\u2019t reliable enough for useful computations due to high optical loss; photons are absorbed or scattered as they pass through optical components, introducing errors. Xanadu aims to minimize these losses over the next two years by developing better components<\/a> and optimizing architecture. The company plans to start building a quantum data center<\/a> in 2029.<\/p>\n

IBM also expects to hit a major modular quantum-computing milestone this year. The company has designed a processor called Flamingo, which pairs two 156-qubit Heron processors with a built-in quantum communication link<\/a>. Later this year, IBM plans to connect up to seven Herons to create a modular Flamingo processor with more than 1,000 qubits.<\/p>\n

Modularity has always been central to IBM\u2019s quantum road map, says Oliver Dial, the chief technology officer of IBM Quantum. While the company has often led the field in packing more qubits into processors, there are limits to chip size. As they grow larger, wiring up the control electronics becomes increasingly challenging, says Dial. Building computers with smaller, testable, and replaceable components simplifies manufacturing and maintenance.<\/p>\n

However, IBM is using superconducting qubits<\/a>, which operate at high speeds and are relatively easy to fabricate but are less network-friendly than other quantum technologies. These qubits operate at microwave frequencies and so can\u2019t easily interface with optical communications<\/a>, which required IBM to develop specialized couplers to connect both adjacent chips and more distant ones.<\/p>\n

IBM is also researching quantum transduction<\/a>, which converts microwave photons into optical frequencies that can be transmitted over fiber optics<\/a>. But the fidelity of current demonstrations is far from what is required, says Dial, so transduction isn\u2019t on IBM\u2019s official road map yet.<\/p>\n

\"AnIBM plans to connect up to seven of its 156-qubit Heron processors to deliver a modular, 1,000+ qubit Flamingo processor this year.IBM<\/p>\n

Trapped-ion and neutral-atom-based qubits interact directly with photons, making optical networking<\/a> more feasible. Last October, IonQ demonstrated<\/a> the ability to entangle trapped ions on different processors. Photons entangled with ions on each chiptravel through fiber-optic<\/a> cables and meet at a device called a Bell-state analyzer<\/a>, where the photons are also entangled and their combined state is measured. This causes the ions that the photons were originally entangled with to become linked via a process called entanglement<\/a> swapping.<\/p>\n

Scaling this up to link large numbers of quantum processors will require a lot of work, says John Gamble, senior director of system architecture<\/a> and performance at IonQ. Bell-state analyzers, currently implemented using free-space optical components, will need to be miniaturized and fabricated using integrated photonics<\/a>. Additionally, optical fiber is noisy, meaning the quality of the entanglement created through those channels is relatively low. To address this, IonQ plans to generate many weakly entangled pairs of qubits and carry out operations to distill those into a smaller number of higher-quality entanglements. But achieving a high enough rate of quality entanglements will remain a challenge.<\/p>\n

The French startup Welinq is addressing this issue by incorporating a quantum memory<\/a> into its interconnect. CEO Tom Darras says one reason why entanglement over photonic interconnects<\/a> is so inefficient is that the two photons required are often emitted at different times, so they \u201cmiss\u201d one another and fail to entangle. Adding a memory creates a buffer that helps synchronize the photons.<\/p>\n

\u201cWhen you need them to meet, they actually meet,\u201d says Darras. \u201cThese technologies enable us to create entanglement fast enough so that it will be useful for distributed computation.\u201d<\/p>\n

Functional Modular Quantum Computers Need More Steps<\/p>\n

Once multiple processors are linked, the challenge shifts to running quantum algorithms<\/a> across them. That\u2019s why Welinq has also developed a quantum compiler, called araQne, that determines how to partition an algorithm across multiple processors while minimizing communication overhead.<\/p>\n

Researchers from Oxford University<\/a> made a recent breakthrough on this front<\/a>, with the first convincing demonstration of a quantum algorithm running across two interconnected processors. The researchers performed logical operations between two trapped-ion qubits on different devices. The qubits had been entangled using a photonic connection, and the processors executed a very basic version of Grover\u2019s search algorithm.<\/p>\n

The final piece of the puzzle will be figuring out how to adapt error-correction schemes for this new modular future. The startup Nu Quantum recently demonstrated<\/a> that distributed quantum error correction<\/a> is not only feasible but efficient.<\/p>\n

\u201cThis is a really big result because, for the first time, distributed quantum computing and modularity is a real option,\u201d says Nu Quantum\u2019s CEO, Carmen Palacios-Berraquero. \u201cBefore, we didn\u2019t know how we would do it in a fault-tolerant<\/a> way, if it was efficient, or if it was viable.\u201d<\/p>\n

This article appears in the March 2025 print issue.<\/p>\n

This article was updated on 7 March 2025 to correct IBM\u2019s plans for its modular Flamingo processor. The company intends to connect seven Heron processors, not three Flamingo processors, and the result is not expected to be the biggest quantum computer to date.<\/p>\n

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