Vasic Working to Ensure Accuracy in Quantum Computing

ECE professor Bane Vasic specializes in error correction codes, which ensure that the information shared and calculated by computers is properly decoded before arriving at its destination. He also studies fault tolerance, or the ability of a computer or network of computers to continue functioning when one or more of its components fails.

Vasić, who also serves as director of the Error Correction Laboratory, has been instrumental in developing a class of error correction codes – called low-density parity check codes, or LDPC codes – used widely in classical communications and data storage. In a project funded by $1.1 million from the National Science Foundation, Vasić is partnering with Saikat Guha in the James C. Wyant College of Optical Sciences to test the feasibility of quantum LDPC codes in quantum computers for the first time.

"Through quantum computing, we will be able to analyze very complicated phenomena, and to solve problems that are not solvable by classical computers. And this will be done very fast," Vasić said. "There are applications in biology; medicine; finances; the simulation of physical, chemical and biological systems; the discovery of new materials; and the design of molecules."

Error correcting codes entangle quantum bits – or qubits – in a very specific way so that qubits stabilize each other. Vasić's decoders allow qubits to pass information about one another back and forth. Similar message passing algorithms are used in artificial intelligence. None of the individual bits have a complete knowledge of value of other bits, but together – through message passing – they collectively learn if there are errors and exactly which bits they are located in. This new project focuses on developing a quantum version of such artificial intelligence algorithms.

"The biggest advantage of LDPC codes is that they support these kinds of message-passing algorithms, which are fault tolerant," Vasić said. "In quantum systems, we have to have fault tolerance, because, due to the higher level of noise, quantum gates are orders of magnitude noisier and more unreliable than classical logic gates... This is a missing piece to realize quantum computers and networks. These quantum LDPC codes are the next generation of codes that will be used, but we have to develop algorithms to decode efficiently and fault-tolerantly."