Bigger, faster quantum computers: this new idea could be the fastest route to real-world applications



Rigetti launched the multichip device with the goal of reaching 80 qubits later this year, up from 31 qubits currently supported by the company’s Aspen processor.

Image: Computer Rigetti

Figuring out how to pack as many high-quality qubits as possible onto a single quantum processor is a challenge that still pisses most researchers off their heads – but now quantum startup Rigetti Computing has come up with a radically new approach to the problem.

Instead of focusing on increasing the size of a single quantum processor, Rigetti tied several smaller chips together to create, instead, a modular processor that still has a higher overall number of qubits.

Describing the technology as the “world’s first multi-chip quantum processor,” the company launched the device with the goal of reaching 80 qubits later this year, up from the 31 qubits currently supported by its Aspen processor.

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At that time, the new quantum system will be available to Rigetti customers on the company’s Quantum Cloud Services platform.

“We have developed a fundamentally new approach to evolving quantum computers,” said Chad Rigetti, founder of Rigetti Computing. “Our proprietary innovations in chip design and manufacturing have opened up what we believe is the fastest way to build the systems needed to run practical applications and correct errors.”

Like IBM and Google, Rigetti’s quantum systems are based on superconducting qubits, which are arrayed on a processor where they are coupled and controlled using microwave pulses. The qubits are also connected to a resonator and associated wiring, which allows the system to encode, manipulate, and read quantum information.

Qubits have special quantum properties that should give quantum computers unprecedented computing power. But for that to happen, processors will need to pack a significant number of qubits – far more than they currently do.

For quantum computers to start generating value early on, experts predict that at least 1,000 qubits will be needed; and one million qubits is often cited as a threshold for the most useful applications. In contrast, the most powerful quantum processors currently support less than 100 qubits.

Increasing the number of qubits on a single processor is difficult, however. This is mainly due to the fragility of qubits, which must be kept in ultra-protected environments colder than space to ensure they remain in their quantum state. More qubits on a chip therefore inevitably means more potential for failure and lower manufacturing yields.

Instead, Rigetti offers to connect several identical processors, such as the ones the company is already able to reliably manufacture, into a large-scale quantum processor.

“This modular approach exponentially reduces manufacturing complexity and enables accelerated and predictable scale-up,” the company said.

According to Rigetti, this will also allow future systems to scale in a multiplicative fashion, as individual chips increase their number of qubits, and new technologies allow more of these chips to be connected to larger processors.

With scale being a top priority for virtually every organization in the quantum ecosystem, Rigetti’s relaunch may well give the startup a competitive edge, even in an industry populated by tech giants like Google, IBM, Microsoft and others. Amazon.

IBM recently unveiled a roadmap for its quantum hardware that aims to build a 1,121-qubit device for release in 2023.

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And smaller players are emerging now, often with the goal of exploring alternatives to superconducting qubits that could allow quantum computers to grow faster. British start-up Quantum Motion, for example, recently published the results of an experiment with qubits on silicon chips.

“There is a race to go from the tens of qubits that devices have today to the thousands of qubits that future systems will need to solve real-world problems,” said Amir Safavi-Naeini, assistant professor of applied physics. at Stanford University. “Rigetti’s modular approach demonstrates a very promising way of approaching these scales.”

As Rigetti’s latest announcement demonstrated, new approaches, methods and technologies are constantly developing in the quantum ecosystem. A clear path is unlikely to emerge anytime soon.


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