Quantum computers have the potential to solve problems that are completely impossible for classical computers, ranging from cryptography for national defense to face recognition and drug development. Just as the transistor is the building block of all modern digital circuits, the quantum bit (aka the qubit) is the heart of a quantum computer. Superconducting qubits, which are essentially artificial two-level atoms that can be designed and fabricated using integrated circuit technology, have emerged as one of the top candidates for realizing scalable quantum information processing. In order to perform quantum computation successfully, quantum computing circuits must be able to transfer quantum information rapidly among a large number of qubits with high fidelity. However, because existing protocols for quantum information transfer (QIT) are in general an order of magnitude slower than single qubit gates, QIT has become the bottleneck for quantum computation. Furthermore, conventional methods of QIT either require a large amount of on-chip real estate or have relatively low quality factor leading to lower efficiency and fidelity. Therefore, it is difficult to scale up qubit circuits to a practically useful size with these protocols. The focus of this project is to demonstrate the basic elements of a novel method of quantum information transmission in superconducting qubit circuits. This new approach uses "dual-rail arrays of negative-inductance Superconducting QUantum Interference Devices (nSQUIDs)" as the information transmitting structures for significant improvement over the current state-of-the-art QIT protocols. The negative mutual inductance between the branches of an nSQUID assigns the two tasks of processing and transferring quantum information to different parts of the nSQUID circuit and therefore makes it possible to optimize parameters of each part for its particular task, so that much faster QIT can be achieved. The success of the project will thus remove one of the most critical roadblocks to building quantum computers. Therefore, knowledge and insights gained from the project activities can be readily applied to other superconducting qubit based quantum computing circuits.
Quantum information research has emerged as a highly competitive cutting edge research field which is actively pursued by all major nations around the world. It is critically important to national security and to maintaining United States' leadership position in scientific discoveries and technological innovations. This collaborative project between theoretical and experimental groups in quantum circuit physics provides a good opportunity for education and training of the graduate and undergraduate students in one of the frontiers of scientific exploration. The project also includes significant outreach and education activities such as improving the undergraduate and graduate classes in Quantum Computing developed with previous NSF support at the University of Kansas and Stony Brook University; involving undergraduates into quantum information research at Kansas; and presenting colloquia on quantum information at local high schools, colleges and universities.
