Scientists have modified a microwave circulator to be used in quantum computers. This allows for the precise tuning of the nonreciprocity between a qubit (the basic unit of quantum computing) and a microwave-resonant cavity. Being able to precisely tune this nonreciprocity is an important tool for quantum information processing. The team has also developed a general and widely applicable theory that simplifies and expands on previous understandings of nonreciprocity. This will allow future work on similar topics to benefit from the team’s model, even when using different components.
A team of scientists at the University of Massachusetts Amherst has modified a microwave circulator for use in quantum computers. This allows for the precise tuning of the degree of nonreciprocity between a qubit and a microwave-resonant cavity, a fundamental unit of quantum computing. The ability to finely adjust the degree of nonreciprocity is crucial for quantum information processing. The team, along with collaborators from the University of Chicago, has developed a general theory that simplifies and expands the capabilities of quantum computers.Based on previous knowledge of nonreciprocity, the team’s model was developed to benefit future research on similar topics, even with different components and platforms. The findings were recently published in Science Advances.
Quantum computing is fundamentally different from traditional bit-based computing. While bits are expressed as 0 or 1 and form the basis of our electronic world, quantum computing relies on “qubits,” which are similar to bits but have unique properties.This article discusses the concept of “quantum superposition” and how it affects the behavior of quantum objects. When in a quantum state, matter behaves differently, allowing qubits to exist as both 0s and 1s simultaneously. This unique property, defined by the laws of quantum mechanics, is what gives quantum computers increased power capabilities.
In addition to quantum superposition, the property of “nonreciprocity” also opens up new opportunities for quantum computing to harness the potential of the quantum world.
Sean van Gelde uses the analogy of a conversation between two people to illustrate these concepts., and one of the paper’s authors, explains that it is essential to create a balance in which each person in the conversation shares an equal amount of information. In quantum computing, total reciprocity is highly sought after as it allows for ample access to data without compromising its integrity. Assistant professor of physics at UMass Amherst, Chen Wang, emphasizes the importance of this balance in computing scenarios to prevent anyone from altering or degrading the data. To address nonreciprocity, lead author Ying-Ying Wang, a graduate student in physics at UMass Amherst, highlights the need for creating an equilibrium to ensure fair sharing of information.In this study, Amherst and her colleagues conducted simulations to determine the necessary design and properties of their circulator in order to control its nonreciprocity. After building the circulator, they performed a series of experiments to not only validate their concept, but also to gain a better understanding of how their device achieved nonreciprocity. Through this process, they were able to simplify their initial model, which had 16 parameters, to a more general model with only six parameters. This revised model is more practical and applicable than the original specific one.The team created an “integrated nonreciprocal device” that resembles a “Y” shape. In the center of the “Y” is the circulator, which acts as a roundabout for the microwave signals that mediate quantum interactions. One leg of the “Y” is the cavity port, a resonant superconducting cavity that contains an electromagnetic field. Another leg of the “Y” holds the qubit, which is printed on a sapphire chip. The final leg is the output port.
Ying-Ying Wang explains that by changing the superconducting electromagnetic field with photons, they observed that it has broad applicability to various future research endeavors.Qubits respond in a way that can be predicted and controlled, allowing us to adjust the level of reciprocity we desire. The simplified model we created describes our system in a way that enables us to calculate external parameters to fine-tune the level of nonreciprocity.”
“This is the first time we have incorporated nonreceptivity into a quantum computing device,” says Chen Wang, “and it paves the way for engineering more advanced quantum computing hardware.”
Funding for this research was provided by the U.S. Department of Energy, the Army Research Office, Simons Foundation, Air Force Office of Scientific Research.Research, the U.S. National Science Foundation, and the Laboratory for Physical Sciences Qubit Collaboratory.
