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“Giant atoms” allow for quantum processing and bonding in one



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MIT researchers have introduced a quantum computing architecture that can perform quantum computations with low error as well as rapidly exchanging quantum information between processors. The work is a key step towards a complete quantum computing platform.

Prior to this discovery, small-scale quantum processors successfully performed tasks at speeds exponentially faster than conventional computers. However, it was difficult to control the transfer of quantum information between remote parts of the processor. In classic computers, wired connections are used to route information back and forth throughout the processor during computing. However, in a quantum computer, the information itself is quantum-mechanical and fragile, requiring fundamentally new strategies to simultaneously process and transmit quantum information on the chip.

“One of the major challenges in scaling quantum computers is the ability to allow quantum bits to interact with each other when they̵

7;re not together,” said William Oliver, associate professor of electrical engineering and computer science at MIT Lincoln Laboratory and associate director of research. electronics laboratories. “For example, the qubits of the nearest neighbors can easily interact, but how do I make” quantum relationships “that connect qubits in distant places?”

The answer is to go beyond the usual interactions of light matter.

Although natural atoms are small and point relative to the wavelength of light with which they interact, in an article published in the journal Nature, researchers show that this should not be the case with superconducting “artificial atoms”. Instead, they built “giant atoms” from superconducting quantum bits or qubits connected in a tuned configuration to a microwave or waveguide line.

This allows researchers to adjust the strength of the qubit-waveguide interaction so that fragile qubits can be protected from degeneracy, or a kind of natural decay that would otherwise be accelerated by the waveguide by performing high-precision operations. After performing these calculations, the strength of the qubit-waveguide connections is regulated, and the qubits can emit quantum data into the waveguide in the form of photons or light particles.

“The connection of a qubit to a waveguide is usually quite bad for cubic operations, as this can significantly shorten the life of the qubit,” said Bharat Kanan, an MIT graduate and the first author of the article. “However, a waveguide is needed to output and route quantum information throughout the processor. Here we have shown that qubit coherence can be maintained even if it is strongly associated with the waveguide. We then have the ability to determine when we want to release information that stored in qubits. We have shown how giant atoms can be used to turn on and off interaction with a waveguide. “

The system implemented by researchers is a new mode of interaction of light matter – say researchers. Unlike models that view atoms as point-like objects smaller than the wavelength of light with which they interact, superconducting qubits, or artificial atoms, are essentially large electrical circuits. In combination with a waveguide, they create a structure as large as the wavelength of microwave light with which they interact.

The giant atom emits its information in the form of microwave photons in several places along the waveguide, so that the photons interfere with each other. This process can be configured for complete destructive intervention, ie the information in the qubit is protected. In addition, even when photons are not actually released from a giant atom, many qubits along the waveguide are still able to interact with each other to perform operations. The qubits remain strongly adhered to the waveguide at all times, but due to this type of quantum interference they can remain unaffected and protected from decoherence, while one- and two-qubit operations are performed with high accuracy.

“We use the effects of quantum interference provided by giant atoms to prevent qubits from emitting their quantum waveguide information until we need it.” says Oliver.

“This allows us to experimentally explore a new regime of physics that is difficult to access with natural atoms,” says Cannan. “The influence of a giant atom is extremely pure and easy to observe and understand.”

The work seems to have a lot of potential for further research, Cannan adds.

“I think one of the surprises is actually the relative ease with which superconducting qubits can enter this giant atomic regime.” he says. “The tricks we used are relatively simple, and as such, you can imagine how to use it for further applications at no extra cost.”

The coordination time of the qubits included in the giant atoms, ie the time when they remain in the quantum state, was about 30 microseconds, almost the same for qubits not associated with a waveguide having a range between 10 and 100 microseconds, the researchers.

In addition, the study demonstrates the operation of entangling two qubits with 94 percent accuracy. This is the first time researchers have cited two-qubit fidelity to qubits that have been strongly associated with a waveguide, because the fidelity of such operations using ordinary small atoms in such an architecture is often low. With increasing calibration, setup procedures, and optimized equipment design, Kanan says, fidelity can be improved.


Array of Rydberg strontium atoms demonstrate prospects for use in quantum computers


More information:
Quantum electrodynamics of a waveguide with superconducting artificial atoms of a giant, Nature (2020). DOI: 10.1038 / s41586-020-2529-9, www.nature.com/articles/s41586-020-2529-9

Provided by the Massachusetts Institute of Technology



Citation: “Giant Atoms” allows quantum processing and communication in one (2020, July 29), received on July 29, 2020 from https://phys.org/news/2020-07-giant-atoms-enable-quantum.html

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