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Physicists have discovered a potentially revolutionary feature of the behavior of quantum bits that would allow scientists to simulate complex quantum systems without the need for enormous computing power.
For some time, the development of the next generation of quantum computers has been limited by the processing speed of conventional processors.
Even the world’s fastest supercomputers haven’t been powerful enough, and existing quantum computers are still too small to be able to model medium-sized quantum structures, such as quantum processors.
However, a team of researchers from the universities of Loughborough, Nottingham and Innopolis have now found a way to circumvent the need for such enormous amounts of energy by exploiting the chaotic behavior of qubits – the smallest unit of digital information.
When modeling the behavior of quantum bits (qubits), they found that when an external energy source, such as a laser or microwave signal, was used, the system became more chaotic – ultimately demonstrating the phenomenon. known as hyperchaos.
When the qubits were energized by the power source, they would change states, like regular computer bits that move between 0 and 1, but in a much more irregular and unpredictable way.
However, the researchers found that the degree of complexity (hyperchaos) did not increase exponentially as the size of the system increased – as one would expect – but on the contrary, it remained proportional to the number of units.
In a new paper, Emergence and control of complex behaviors in controlled systems of qubits interacting with dissipation, published in the journal Nature Quantum information NPj, the team shows how this phenomenon has great potential to allow scientists to simulate large quantum systems.
One of the corresponding authors, Dr Alexandre Zagoskin, of the Loughborough School of Science, said: “A good analogy is the design of airplanes.
“To design an airplane, it is necessary to solve certain hydro (aero) dynamics equations, which are very difficult to solve and which only became possible after World War II, when powerful computers appeared.
“Nonetheless, people had designed and flown airplanes long before that.
“This was because the behavior of the airflow could be characterized by a limited number of parameters, such as Reynolds number and Mach number, which could be determined from small-scale model experiments.
“Without this, direct simulation of a quantum system in all detail, using a classical computer, becomes impossible once it contains more than a few thousand qubits.
“Essentially, there isn’t enough material in the Universe to build a conventional computer that can handle the problem.
“If we can characterize different regimes of a 10,000-qubit quantum computer by just 10,000 of these parameters instead of 2 ^ (10,000) – which equates to about 2 times a 1 with three thousand zeros – that would be a real breakthrough. “
The new results show that a quantum system presents qualitatively different models of general case behavior, and the transitions between them are governed by a relatively small number of parameters.
If this is generally the case, researchers will be able to determine the critical values of these parameters from, for example, the construction and testing of scale models, and, by taking some measurements of the real system, to tell whether the parameters of our quantum processor let it work fine or not.
As a bonus, the controllable complexity of the behavior of large quantum systems opens up new possibilities in the development of new quantum cryptography tools.
Dr Weibin Li, School of Physics and Astronomy, University of Nottingham, said: “The results of this work are revealing for understanding complex quantum dynamics.
“Future quantum computers are made up of thousands of quantum bits (qubits), which will be orders of magnitude more powerful than the fastest conventional computer on the market.
“Here, the complete control and characterization of quantum computers is the key to performing a correct and massive calculation.
“In the quantum domain, the number of degrees of freedom of a system increases exponentially with its size.
“In large scale quantum computing on a true quantum computer is not yet available, the bottleneck is that only small-scale quantum computers, up to tens of qubits, can be simulated using conventional supercomputers.
Reference: “Emergence and control of complex behaviors in qubit driven systems interacting with dissipation” by AV Andreev, AG Balanov, TM Fromhold, MT Greenaway, AE Hramov, W. Li, VV Makarov and AM Zagoskin, January 4, 2021, Quantum information NPj.
DOI: 10.1038 / s41534-020-00339-1
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