This startup has built a record-breaking 256-qubit quantum computer


In 2019, Google announced that its 53-qubit machine had achieved quantum hegemony-performing tasks that traditional computers could not manage-but IBM questioned this claim. In the same year, IBM introduced a 53-bit quantum computer. In 2020, IonQ launched a 32-qubit system, which the company called “the most powerful quantum computer in the world.” Just this week, IBM introduced a new 127-qubit quantum processor, which the press release called “a little miracle of design.” Jay Gambetta, vice president of quantum computing at IBM, said: “In my opinion, the biggest news is that it works.”

QuEra now claims to have manufactured far more qubit devices than any competitor.

Of course, the ultimate goal of quantum computing is not to play Tetris, but to overcome classical computers in solving practically interesting problems. Fanatics believe that when these computers become powerful enough, perhaps within a year or two, they may have a transformative impact in fields such as medicine and finance, neuroscience, and artificial intelligence. A quantum machine may require thousands of qubits to manage such complex problems.

However, the number of qubits is not the only important factor.

QuEra also advertises the enhanced programmability of its device, where each qubit is a single ultracold atom. These atoms are precisely arranged by a series of lasers (called optical tweezers by physicists). Positioning qubits allows the machine to be programmed, adjusted to the problem under study, and even reconfigured in real time during the calculation process.

“Different problems require atoms to be placed in different configurations,” said Alex Keesling, CEO of QuEra and co-inventor of the technology. “The uniqueness of our machine is that every time we run it, several times per second, we can completely redefine the geometry and connectivity of the qubit.”

Atomic advantage

QuEra’s machine is built on blueprints and technology that has been improved over the years, and is led by Mikhail Lukin and Markus Greiner of Harvard and Vladan Vuletić and Dirk Englund of MIT (both in the founding team of QuEra). In 2017, the early device model of the Harvard team used only 51 qubits; in 2020, they demonstrated a 256-qubit machine. The QuEra team hopes to reach 1,000 qubits within two years, and then, without making too many changes to the platform, they hope to continue to expand the system to more than hundreds of thousands of qubits.

Mario made of QuEra qubits
Mario made of QuEra qubits.

Ahmed Omran/Quila

QuEra’s unique platform—the physical way the system is assembled, and the method of information encoding and processing—should allow a leap of this scale.

Google and IBM’s quantum computing systems use superconducting qubits, while IonQ uses trapped ions, while QuEra’s platform uses an array of neutral atoms to produce qubits with impressive coherence (ie, a high degree of “quantum”). The machine uses laser pulses to cause atoms to interact and excite them to an energy state-a “Rydberg state”, described by the Swedish physicist Johannes Ridberg in 1888-here In this state, they can perform quantum logic with high fidelity in a robust manner. This Rydberg method of quantum computing has been studied for decades, but it requires technological advancements—such as lasers and photonics—to make it work reliably.

“Irrational Exuberance”

When the computer scientist, director of the Berkeley Center for Quantum Computing, and computer scientist Umesh Vazirani first learned of Lukin’s research along these directions, he felt “extraordinarily excited”—it seemed a wonderful method, even though Vazirani questioned him Does his intuition match reality? “We have various mature paths, such as superconductors and ion traps, which have been studied for a long time,” he said. “Should we not consider different options?” He consulted with John Preskill, a physicist and director of the Institute of Quantum Information and Matter at the California Institute of Technology, who assured Vazirani that his prosperity was It makes sense.

Preskill found that the Rydberg platform (not just QuEra’s) is interesting because they produce highly entangled, strongly interacting qubits—”This is where the quantum magic is,” he said. “I am very excited about the potential to discover unexpected things in a relatively short period of time.”

In addition to simulating and understanding quantum materials and dynamics, QuEra is also committed to researching quantum algorithms for solving NP-complete (ie, very difficult) computational optimization problems. “These are indeed the first examples of useful quantum advantages involving scientific applications,” Lu Jin said.

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