The computing power of quantum machines is currently very low. Expansion is always a big deal. Physicists are now presenting a new architecture for global quantum computers that overcomes these limitations and could soon form the basis for the next generation of quantum computers.
In a quantum computer, a quantum bit (qubit) plays the role of a unit of calculation and memory. Since quantum information cannot be copied, it cannot be stored in memory as in classical computers. Because of this limitation, all qubits in a quantum computer must be able to interact with each other. It remains a huge challenge to build a powerful quantum computer. In 2015, theoretical physicist Wolfgang Leschner, together with Philip Hooke and Peter Zoller, accepted this challenge and proposed a new architecture for quantum computers, now called the LHZ architecture in honor of the authors.
"This geometry was originally designed to solve optimization problems," recalls Wolfgang Lechner of the Department of Theoretical Physics at the University of Innsbruck in Austria. "In the process, we scaled back the architecture to address these optimization issues as efficiently as possible." In this architecture, physical qubits do not represent individual bits, but rather represent the relative coordination between bits. "This means that all the qubits no longer need to interact with each other," explains Wolfgang Leschner. Now he and his team have shown that this concept of valence also applies to universal quantum computers.
Complex operations simplified
An equivalent computer can perform operations between two or more bits on a single qubit. "Quantum computers have performed very well on small-scale operations," said Michael Fellner of the Wolfgang Lechner group. "However, as the number of qubits increases, the implementation of these gate operations becomes more and more complex." In two publications in the journal Physical Review Letters and Physical Review A , the Innsbruck scientists have now shown that stoichiometric computers can perform, for example, quantum Fourier transforms, the basis of many quantum algorithms, with fewer computational steps and therefore faster. . "The high parallelism of our architecture means, for example, that Shor's famous algorithm can work very efficiently for analyzing numbers," Fellner said.
Two-step error correction
This new concept also offers technically effective error correction. Because quantum systems are very sensitive to interference, quantum computers must constantly correct errors. Significant resources must be devoted to protecting quantum information, which greatly increases the number of qubits required. "Our model works with two-step error correction, where one type of error (bit translation error or phase error) is avoided by the hardware used," explained Anette Messinger and Kilian Ender, members of the research team at Innsbruck. There is already an early beta approach to this on multiple platforms. “Other types of bugs can be detected and fixed by software,” Messinger and Ender explain. This will enable the implementation of the next generation of voltage-controlled universal quantum computers. ParityQC, a spin-off co-founded by Wolfgang Lechner and Magdalena Hauser, is already working with scientific and industrial partners in Innsbruck on the possible implementation of the new model.
The research carried out at the University of Innsbruck was supported by the Austrian Science Foundation FWF and the Austrian Research Promotion Agency FFG.
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