This new startup built a 256-qubit quantum computer that broke records

In 2019, Google announced that its 53-qubit machine had achieved quantum supremacy, performing a task that could not be handled by a conventional computer, but IBM challenged the claim. The same year, IBM released its 53-bit quantum computer. In 2020, IonQ unveiled a 32-qubit system that the company said was the “most powerful quantum computer in the world.” And this week, IBM released its new 127-qubit quantum processor, which the press release described as a “little design miracle.” “The big news, from my perspective, is that it works,” says Jay Gambetta, IBM’s vice president of quantum computing.

Now QuEra claims to have made a device with far more qubits than any of those rivals.

The ultimate goal of quantum computing, of course, is not to play Tetris, but to surpass classical computers in solving problems of practical interest. Enthusiasts acknowledge that when these computers become powerful enough, perhaps in a decade or two, they could bring transformative effects in fields like medicine and finance, neuroscience and artificial intelligence. Quantum machines likely need thousands of qubits to handle such complex problems.

However, the number of qubits is not the only factor that matters.

QuEra is also touting its device’s improved programmability, in which each qubit is a single ultra-cold atom. These atoms are precisely arranged with a series of lasers (physicists call them optical tweezers). The positioning of the qubits allows programming the machine, adjusting it to the problem under investigation and even reconfiguring it in real time during the calculation process.

“Different problems will require the atoms to be placed in different configurations,” says Alex Keesling, CEO of QuEra and a co-inventor of the technology. “One of the unique things about our machine is that every time we run it, a few times per second, we can completely redefine the geometry and connectivity of the qubits.”

The advantage of the atom

The QuEra machine was built from a plan and technologies refined over several years, led by Mikhail Lukin and Markus Greiner at Harvard and Vladan Vuletić and Dirk Englund at MIT (all are on the founding team of QuEra). In 2017, an earlier model of the Harvard group’s device used only 51 qubits; In 2020, they demonstrated the 256 qubit machine. Within two years, the QuEra team hopes to hit 1,000 qubits and then, without changing the platform much, they hope to continue expanding the system beyond hundreds of thousands of qubits.

Mario made of qubits by QuEra
Mario made from QuEra qubits.


It is QuEra’s unique platform, the physical way the system is assembled, and the method by which information is encoded and processed, that should allow for such leaps of scale.

While Google and IBM’s quantum computing systems use superconducting qubits, and IonQ uses trapped ions, the QuEra platform uses arrays of neutral atoms that produce qubits with impressive coherence (that is, a high degree of “quantum”). The machine uses laser pulses to make the atoms interact, exciting them to an energy state, a “Rydberg state”, described in 1888 by Swedish physicist Johannes Rydberg, in which they can do quantum logic in a robust way with high fidelity. This Rydberg approach for quantum computing It has been in the works for a couple of decades, but technological advances were needed, for example with lasers and photonics, to make it work reliably.

“Irrationally exuberant”

When computer scientist Umesh Vazirani, director of the Berkeley Center for Quantum Computing, first learned of Lukin’s research in this regard, he felt “irrationally exuberant.” It seemed like a wonderful approach, although Vazirani questioned whether his intuitions were in the wrong. contact with reality. “We have had several well-developed pathways, such as superconductors and ion traps, that have been worked on for a long time,” he says. “Shouldn’t we think of different schemes?” He contacted John Preskill, a physicist at the California Institute of Technology and director of the Institute for Quantum Matter and Information, who assured Vazirani that his exuberance was justified.

Preskill finds the Rydberg platforms (not just QuEra’s) interesting because they produce strongly interacting and highly entangled qubits, “and that’s where the quantum magic is,” he says. “I’m very excited about the potential on a relatively short time scale to discover unexpected things.”

In addition to simulating and understanding materials and quantum dynamics, QuEra is working on quantum algorithms to solve computational optimization problems that are NP-complete (that is, very difficult). “These are really the first examples of useful quantum advantages involving scientific applications,” says Lukin.

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