Credit: CC0 Public Domain
Quantum computing is expected to be worth $65 billion by 2030. This market is a hot topic for both investors and scientists due to its ability to solve complex, incomprehensible problems.
One example is drug discovery. A pharmaceutical company may want to model the interaction between two molecules in order to understand drug interactions. Scientists must model the various ways these atoms could arrange themselves after their respective molecules are introduced. This is a challenge because each molecule is made up of several hundred atoms. There are infinite possibilities for configurations, more than there are atoms in the universe. A quantum computer cannot represent or solve such a vast, dynamic data problem.
While mainstream quantum computing is still decades away, research teams at universities and in the private sector around the world continue to work on different aspects of the technology.
Xu Yi is an assistant professor of electrical and computer Engineering at the University of Virginia School of Engineering and Applied Science. His research group has carved a niche within the physics and application of photonic devices. These devices detect and shape light and can be used for a variety of purposes, including computing and communications. His research group created a quantum computing platform that is scalable and can be scaled to meet quantum speed requirements. It's a tiny photonic chip, the size of a penny.
This success was made possible by Olivier Pfister (professor of quantum optics and quant information at UVA) and Hansuek Lee (assistant professor at the Korean Advanced Institute of Science and Technology).
Nature Communications published the experimental results of the team, "A Squeezed Quantum Microcomb On a Chip", in a recent publication. Zijiao Yang (a Ph.D. candidate in physics) and Mandana Jahanbozorgi (a Ph.D. candidate in electrical and computer engineering), are two of Yi's team members. This research was supported by a grant from the National Science Foundation's Engineering Quantum Integrated Platforms for Quantum Communication program.
Quantum computing promises a completely new way to process information. The information processed by your laptop or desktop computer is in long strings. A bit can only hold one value: one or zero. Quantum computers can process information simultaneously, meaning they don't need to wait for one sequence to be processed before they can calculate more. A qubit is their unit of information, which can be both one or zero simultaneously. Qumode is a quantum mode that spans all the variables within the range of one to zero, the values right of the decimal point.
Researchers are developing new methods to efficiently create the large number of qumodes required to reach quantum speeds.
Yi's photonics-based method is appealing because a spectrum of light can also be a full spectrum. Each light wave within the spectrum could potentially become a quantum unit. Yi predicted that the quantum state would be achieved by entangling light fields.
You may be familiar with optical fibers, which transmit information via the internet. Multiplexing is the use of multiple lasers in parallel within an optical fiber. Yi introduced the multiplexing concept to the quantum realm.
Micro is the key to his team's success. UVA is a pioneer in optical multiplexing and the leader in creating scalable quantum computing platforms. Pfister's team was able to generate more than 3,000 quantum modes using bulk optical systems in 2014. This many quantum modes require a large space to house the thousands of lenses, mirrors and other components required to run an algorithm or perform other operations.
Pfister stated that integrated quantum optics is the future of the field. Only by moving quantum optics experiments from protected optical labs to field compatible photonic chips can bona fide quantum tech see the light. We were extremely lucky to be able to bring to UVA a world-renowned expert in quantum photonics, Xu Yi. I am very excited about the new possibilities these results offer us.
Yi's group developed a quantum source within an optical microresonator. This is a ring-shaped structure measuring millimeters in size that surrounds photons. It generates a microcobe which converts photons efficiently from one to multiple wavelengths. To build optical power, light circulates around the ring. This power accumulation increases the chances of photons interfacing, which results in quantum entanglement between microcomb fields of light.
Yi's team demonstrated multiplexing to generate 40 qumodes using a single microresonator. This proved that multiplexing quantum modes in integrated photonic platforms is possible. They can only measure this number.
Yi stated that if the system is optimized, Yi can create thousands of qumodes with a single device.
Yi's multiplexing technique opens the door to quantum computing in real-world situations, where errors are almost inevitable. This is true for classical computers as well. However, quantum states are more fragile than classical ones.
With an increase in devices, the number of qubits required to compensate for errors can exceed one million. Multiplexing can reduce the number of devices required by up to three orders of magnitude.
Yi's photonics-based quantum computing system has two more advantages. Superconducting electronic circuits are required to cool quantum computing platforms. Quantum computers that use photonic integrated chips have no mass so they can be used at room temperature. Lee also fabricated the microresonator using standard lithography methods. This is significant because it means that the resonator/quantum source can be mass produced.
Yi stated that "we are proud to push engineering boundaries in quantum computing and accelerate transition from bulk optics into integrated photonics." Yi stated, "We will continue to look at ways to integrate devices/circuits in a quantum computing platform based on photonics and optimize its performance."
Continue reading The best of both the worlds: Combining quantum and classical systems to meet supercomputing needs
Further information: Zijiao Yan et al., A squeezed quantum microcomb on a silicon chip, Nature Communications (2021). Information from Nature Communications Zijiao Yang and colleagues, A squeezed quantum microcomb on a chips, (2021). DOI: 10.1038/s41467-021-25054-z
