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Physicists At Harvard Made A Huge Step Forward In The Race To Quantum Computing

Physicists At Harvard Made A Huge Step Forward In The Race To Quantum Computing

A group of physicists from the Harvard-MIT Center for Ultracold Atoms and other institutions have constructed a programmable quantum simulator that can operate with 256 quantum bits, or "qubits."

The system is a significant step toward the development of large-scale quantum machines that could be used to shed light on a variety of complex quantum processes and eventually help bring about real-world breakthroughs in material science, communication technologies, finance, and a variety of other fields, overcoming research challenges that are currently beyond the capabilities of even the fastest supercomputers.

Quantum computers work on qubits, which are the essential building pieces and source of their tremendous computing capacity.

Mikhail Lukin, the George Vasmer Leverett Professor of Physics, co-director of the Harvard Quantum Initiative, and one of the senior authors of the work published today in the journal Nature, said, "This advances the discipline into a new realm where no one has ever been before." “We have entered an entirely new realm of quantum physics.”

The combination of the system's unprecedented size and programmability, according to Sepehr Ebadi, a physics student in the Graduate School of Arts and Sciences and the study's lead author, puts it at the cutting edge of the race for a quantum computer, which harnesses the mysterious properties of matter at extremely small scales to greatly advance processing power. In the correct circumstances, the addition of qubits allows the system to store and analyze exponentially more data than traditional bits, which are used in normal computers.

“The amount of quantum states that may be created with only 256 qubits exceeds the number of atoms in the solar system,” Ebadi explained.

Researchers have already used the simulator to view numerous exotic quantum states of matter that had never been observed empirically before, as well as undertake a quantum phase transition study that is so accurate that it serves as a classic example of how magnetism works at the quantum level.

These studies reveal a lot about the quantum mechanics that underpins material properties and can show scientists how to create new materials with unusual features.

The idea makes use of a much improved version of a platform built by the researchers in 2017, which was capable of exceeding 51 qubits in size. Using a one-dimensional array of individually focused laser beams known as optical tweezers, the researchers were able to grab ultra-cold rubidium atoms and arrange them in a specified order.

The atoms can now be built in two-dimensional arrays of optical tweezers using this novel technique. This raises the size of the system that can be built from 51 to 256 qubits. Researchers may construct diverse interactions between the qubits by using the tweezers to arrange the atoms in defect-free patterns and create programmable structures like square, honeycomb, or triangle lattices.

The spatial light modulator, which is used to shape an optical wavefront to produce hundreds of individually focused optical tweezer beams, is the workhorse of this new platform, according to Ebadi. “These devices are essentially the same as those used inside a computer projector to display images on a screen, but we've repurposed them to be a key component of our quantum simulator.”

The researchers must move the atoms around to arrange them into their target shapes because the initial loading of the atoms into the optical tweezers is random. To eliminate the initial unpredictability, the researchers utilize a second set of moving optical tweezers to move the atoms to their targeted places. The researchers can position the atomic qubits and manipulate them in a coherent quantum manner using lasers.

Harvard Professors Subir Sachdev and Markus Greiner, Massachusetts Institute of Technology Professor Vladan Vuleti, and scientists from Stanford, the University of California Berkeley, the University of Innsbruck in Austria, the Austrian Academy of Sciences, and QuEra Computing Inc. in Boston are among the study's senior authors.

Tout Wang, a research associate in physics at Harvard and one of the paper's authors, said, "Our work is part of a really strong, high-visibility global competition to create bigger and better quantum computers."

“Top university research institutes are involved in the whole endeavor [beyond our own] as well as considerable private-sector funding from Google, IBM, Amazon, and others.”

The researchers are also working on making the system more programmable and enhancing laser control over qubits. They're also looking into novel uses for the technology, such as examining strange forms of quantum matter and solving difficult real-world issues that can be naturally encoded on the qubits.

Ebadi stated, "This work enables a wide variety of new research directions." “We haven't even scratched the surface of what these technologies can do.”

The Center for Ultracold Atoms, the National Science Foundation, the Vannevar Bush Faculty Fellowship, the United States Department of Energy, the Office of Naval Research, the Army Research Office MURI, and the DARPA ONISQ program all contributed to this research.

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