This project will develop new theoretical techniques to control and measure coupled mesoscopic quantum systems, focusing on superconducting quantum bits (qubits) and resonators. Such techniques are important in quantum information processing. The first goal is to engineer entangled quantum states of, and joint operations on, two mesoscopic resonators. The second goal is to analyze the tunneling dynamics of a phase qubit, in which the Zeno effect is induced by a continuous measurement. This will help to elucidate the ways in which measurements can be used to control mesoscopic systems. These theoretical studies are relevant to near-future experiments on mesoscopic devices. The project will focus both on short-term experimental demonstrations of NOON states and long-term approaches to scalable quantum information processing.
This project has three kinds of broader impact. First, there will be significant involvement of undergraduate students at Williams, and graduate students at UMass Boston. The latter has the most diverse campus in New England, with a large fraction of minorities. These students will not only be exposed to research, but they will also gain experience in high-performance computing, skills that are becoming increasingly important in industry as well as academia. Students at Williams involved in the research will have access to UMass Boston's parallel computing cluster. Second, the project will develop and support a collaborative effort between Williams College and UMass Boston in parallel with the National Institute of Standards and Technology. Third, the project will contribute to enhancing and maintaining the high-peformance computing facilities at UMass Boston.
This project is theoretical, and consists of two parts. In the first part we will develop new techniques for engineering entangled quantum states of, and joint operations on, two mesoscopic resonators. Such techniques are important in quantum information processing. In the second part we will study the tunneling dynamics of a phase qubit, in which the Zeno effect is induced by a continuous measurement. This will help to elucidate the ways in which measurements can be used to control mesoscopic systems. Both parts of the project are relevant to near-future experiments on mesoscopic devices. The first part of the project resulted in the design and theoretical analysis of techniques to prepare and control the state of two coupled resonators. The primary outcome was a set of algorithms using a quantum bit to digitally program an arbitrary state of the two resonators. A second outcome was the identification of a limit to cooling of a resonator when it is weakly coupled to another. This was accompanied by the design of cooling protocols that achieve greater cooling factors than traditional approaches. The second part of the project analyzed the Zeno effects due to pulsed and continuous measurement of a decaying system, such as a phase qubit. The timescales for this problem were identified and their potential for experimental observation were analyzed. The final result was that the measurements required for decaying systems are much more demanding than for other Zeno effects. In addition to the intellectual merits described above, the broader impacts of our work involve training of students and the improvement of research infrastrcture. We have trained a large number of students (undergraduate and graduate) and two postdoctoral researcheers in the course of this project. This training continues our goals to prepare students for highly qualified study and continued engagement in science and engineering. As part of this project, the supercomputing facilities at UMass have been strengthened and will make a continued impact on future computational studies by the principal investigators. Finally, a collaboration between Williams College and UMass has been strengthened. This collaboration includes access to high performance computing resources, and will make a continued impact on future computational studies by researchers at Williams College.
