Physicists have discovered a potentially game-changing feature of quantum bit behavior that allows scientists to simulate complex quantum systems without the need for massive computing power.
The development of the next generation of quantum computers has been limited for some time by the processing speed of conventional CPUs.
Even the world’s fastest supercomputers have not been powerful enough, and existing quantum computers are still too small to model medium-sized quantum structures, such as quantum processors.
However, a team of researchers from the universities of Loughborough and Nottingham and Innopolis has now found a way to circumvent the need for such vast amounts of power by harnessing the chaotic behavior of qubits – the smallest unit of digital information.
In 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, eventually demonstrating the phenomenon known as hyperchaos.
When the qubits were generated by the power source, they switched states like regular computer bits shifting between 0 and 1, but in a much more erratic and unpredictable way.
However, the researchers found that the degree of complexity (hyperchaos) did not increase exponentially as the size of the system grew – which one would expect – but instead remained proportional to the number of units.
In a new newspaper, Emergence and control of complex behavior in driven systems of interacting with qubits with dissipation, published in the Nature journal NPj Quantum informationshows the team how this phenomenon has great potential for enabling scientists to simulate large quantum systems.
One of the corresponding authors, Dr. Alexandre Zagoskin, from the Loughborough School of Science, said: “A good analogy is the design of aircraft.
“To design an aircraft, it is necessary to solve certain equations of hydro (aero) dynamics, which are very difficult to solve and only became possible long after WWII, when powerful computers appeared.
“Nevertheless, people had designed and flown airplanes long before that.
“It was because the behavior of the airflow could be characterized by a limited number of parameters, such as the Reynolds number and the Mach number, which could be determined from small-scale experiments.
“Without this, a direct simulation of a quantum system in detail, with a classic computer, becomes impossible once it contains more than a few thousand qubits.
“In essence, there is not enough matter in the universe to build a classic computer that can solve the problem.
“If we could characterize different regimes of a 10,000-qubit quantum computer with only 10,000 such parameters instead of 2 ^ (10,000) – which is about 2 times a 1 with 3,000 zeros – that would be a real breakthrough.”
The new results show that a quantum system exhibits qualitatively different patterns of general case behavior, and the transitions between them are determined by a relatively small number of parameters.
If this is general, the researchers can determine the critical values of these parameters by, for example, building and testing scale models, and by taking a few measurements of the actual system, whether the parameters of our quantum processor make it work properly or not.
As a bonus, the manageable complexity in the behavior of large quantum systems opens up new possibilities in the development of new quantum cryptography tools.
Dr. Weibin Li, from the School of Physics and Astronomy, Nottingham University, said, “The results of this work are insightful for understanding complex quantum dynamics.
“Future quantum computers will consist of thousands of quantum bits (qubits), which will be orders of magnitude more powerful than the fastest classical computer on the market.
“Here, full control and characterization of quantum computers is the key to performing correct and extensive computing.
“In the quantum world, the number of degrees of freedom of a system grows exponentially with size.
“On scale quantum computers is not yet available on a real quantum computer, the bottleneck is that only small-scale quantum computers, up to tens of qubits, can be simulated with classic supercomputers. “
Reference: “Emergence and Control of Complex Behavior in Powered Systems of Interacting Qubits with Dissipation” by AV Andreev, AG Balanov, TM Fromhold, MT Greenaway, AE Hramov, W. Li, VV Makarov and AM Zagoskin, January 4, 2021, NPj Quantum information.
DOI: 10.1038 / s41534-020-00339-1