The Yale Tang lab released Thursday a design for a new silicon chip meant to revolutionize quantum information processing, with the aim of making an overall better computer.
The hardware necessary to create a powerful and scalable quantum computer has not yet caught up with the theory behind it, according to professor of electrical engineering, physics and applied physics Hong Tang, head of the Tang lab and paper co-author. To address this problem, Tang's lab at Yale created a silicon chip that integrates the two key functions of a quantum information processor: the ability to detect photons and the ability to manipulate them. The project took about four years to complete
"This technology has the potential to make many important problems much faster to solve," said Carsten Schuck, lead author of the paper. "Applications include everything from, searching a database, making a Google search, cracking cryptographic codes, to simulating complex chemical equations in order to design new drugs."
This potential increased speed comes from the way quantum computers interact with quantum systems. According to Schuck, in a traditional computer, there are bits of information represented in the code of the computer as zeros and ones. One component of the computer, called a transistor, is either on or off, which indicates either a zero or a one.
In a quantum system, such as a single photon or atom, there can be a zero or a one, or there can also be a superposition— a principle, arising from the Schrodinger theory, that information is simultaneously represented in all possible states. Consequently, the information could be represented as zero and one at the same time. Instead of calculating the outcome of the program based on whether a zero or a one was in that position, the system can calculate both potential outcomes simultaneously, because the quantum system can be in both states at the same time, Schuck said.
"The efficiency and the speed can be increased dramatically, compared to the classical computer," Tang said. "Just like how using those classical computers is far faster than working on an Abacus."
In its current form, the chip can perform two simultaneous functions, manipulating photons in order to carry out calculations, and using photon-detectors to measure the results, co-author Xiang Guo said.
The chip is tiny and therefore scalable. According to Tang, scalability is crucial because in order for the technology to be widely accessible, complex systems must be manufacturable. Just as classical computers used to take up entire rooms of space, modern day quantum computers are bulky and not easily accessible, Guo said. Since the chip is very compatible with nanofabrication -— the design and manufacture of devices in the dimensions of nanometers — it is easier to scale up so that more complex calculations can be computed.
The silicon chip was inspired by the chip technology used by technology companies including Samsung and IBM, which have a massive number of applications, Schuck said. By proving that a single circuit performing quantum processing could successfully be put onto a similar chip, the group has shown that it will be feasible to write thousands more circuits carrying out more complex calculations and add them to the existing technology.
The ultimate goal of the project is to create a powerful and efficient, yet scalable quantum computer. That goal is well within reach thanks to the team's success of creating a small silicon chip that does the work of much larger and more inefficient devices, co-author paper and Nanjiang University professor Xiaosong Ma said.
"We used advanced nanofabrication techniques to shrink down the element to a micrometer, or even nanometer scale," Ma said. "One day, we hope that there can be hundreds, or even thousands of elements on a small chip."
The nanofabrication facilities at Yale made it possible for the group to complete this project before other researchers, Schuck said. Given that the project is ongoing, authors agreed that there will likely be future developments to this technology in the next few years. There are key components that they plan to add to future iterations of the chip and they hope a working quantum computer will arise from this research, Tang said.
The Schrödinger theory was proposed by the Austrian physicist Erwin Schrodinger in the year 1935.
