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Quantum state for single electrons controlled by & # 39; surfing & # 39; on sound waves

  Quantum state for single electrons controlled by
Credit: University of Cambridge

Researchers have successfully used sound waves to control quantum information in a single electron, a significant step toward efficient, robust quantum computers made of semiconductors.

The international team, including researchers from the University of Cambridge, sent high-frequency sound waves over a modified semiconductor device to control the behavior of a single electron, with efficiencies over 99 percent. The results are reported in the journal Nature Communications .

A quantum computer could solve previously insoluble computational problems by taking advantage of the strange behavior of particles in the subatomic scale, and quantum phenomena such as confusion and superposition. But precisely controlling the behavior of quantum particles is a huge task.

"What would make a quantum computer so powerful is its ability to scale exponentially," said co-author Hugo Lepage, a Ph.D. candidate in Cambridge's Cavendish Laboratory, who performed the theoretical work for the current study. "In a classic computer, to double the amount of information, you have to double the number of bits. But in a quantum computer, you just need to add one more quantum bit or qubit to double the information." [1

9659005] Last month, Google researchers claimed to have reached "quantum superiority", the point at which a quantum computer can perform calculations beyond the capacity of the most powerful supercomputers. However, the quantum computers that Google, IBM and others develop are based on superconducting loops, which are complex circuits and which all quantum systems are very fragile.

"The slightest fluctuation or deviation will destroy the quantum information in the phases and currents of the loops," said Lepage. "This is still very new technology and expansion beyond the intermediate scale may require us to go down to the individual particle level."

Instead of superconducting loops, the quantum information in the quantum computer Lepage and his colleagues plan to use "spin of an electron – its inherent angular momentum, which can be up or down – to store quantum information.

could lead to a quantum computer that is much more robust because spin interactions are determined by the laws of nature, "Lepage said.

By using spin, quantum information can be more easily integrated with existing systems. The device developed in the current work is based on commonly used semiconductors with some minor modifications.

The unit, which was experimentally tested by Lepage's co-author from Institut Néel, measures only a few million by one meter in length. The researchers then aimed high-frequency sound waves across the device, causing it to vibrate and distort, like a small earthquake. 19659005] The researchers were able to control the behavior of a single electron with 99.5 percent efficiency. "Controlling a single electron in this way is already difficult, but to get to a point where we can have a working quantum computer we must be able to control multiple electrons, which become exponentially more difficult when qubits begin to interact with each other, "Lepage said.

In the coming months, researchers will begin testing the device with multiple electrons, which would bring a working quantum computer one step closer.

Machine learning opens up new possibilities for quantum units

More information:
Shintaro Takada et al. Noise-driven single-electron transmission in a circuit with coupled quantum rails, Nature Communications (2019). DOI: 10.1038 / s41467-019-12514-w

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Quantum state for single electrons controlled by & # 39; surfing & # 39; on sound waves (2019, October 10)
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