Prof. Lev Levitin

Prof. Tommaso Toffoli

Constant advances in technology may make it seem like computing power has infinite potential, but two ECE professors have determined that one day processors will hit an ultimate speed limit.

Department of Electrical & Computer Engineering Distinguished Professor Lev Levitin and Research Professor Tommaso Toffoli recently published new research in Physical Review Letters which shows that while breakthroughs in hardware and quantum computing will continue to produce faster processing speeds for many years, we will one day hit a fundamental ceiling.

“No system can overcome that limit. It doesn’t depend on the physical nature of the system or how it’s implemented, what algorithm you use for computation—any choice of hardware and software,” Levitin said. “This bound poses an absolute law of nature, just like the speed of light.”

Levitin’s research had earlier identified a quantum elementary operation, the simplest possible task that could be performed by a quantum computer. Using this idea, Levitin and Toffoli derived an equation that represents the minimum amount of time it takes for such an operation to occur, for a given amount of energy invested. As quantum computing represents the theoretical limit of computing performance, this time interval illustrates the fastest possible operation rate that could ever be achieved by any computer.

For perspective, contemporary computers typically perform around 10^10 elementary operations per second, while an ideal computer would breeze through 10^20 operations using the same amount of time and energy—effectively making it 10 billion times faster.

While reaching this limit is hindered by current technological limitations, Levitin and Toffoli anticipate that we could hit this barrier within this century.

“If we believe in Moore’s law, it would take only 50 years to achieve this quantum limit.”