Career: Practical Quantum Error Prevention Protocols Involving Quantum Systems With More Than Two Orthogonal States

Southern Illinois University At Carbondale, Carbondale IL

Investigators

Abstract

The computers used today function according to the laws of Newtonian mechanics. These laws govern macroscopic objects. A quantum computer, when one is built, will functions according to the laws of quantum mechanics. These laws govern objects which are very small in size such as individual atoms. The laws of quantum mechanics can be quite different from those of our ordinary experience and have given rise to very curious, but experimentally verifiable, physical phenomena. Since the laws are different, the processes involved in computing with quantum systems are different and in some cases give rise to advantages over the computers of today. This makes the results of quantum mechanical calculations not just curious, but useful. The unit of information storage on the computers of today is called a bit and can take two values, zero and one. The quantum computer envisaged by the pioneers of quantum computing would use quantum states which have two available states, also denoted with a zero and a one. However, whereas it has been shown that systems using more classical states cannot provide an advantage over the bit, advantages exist for quantum systems which use more than two states for quantum information processing. A key resource for quantum computers is a set of highly correlated quantum states called entangled states. Quantum states with more than two states can have a higher degree of correlation and share a larger fraction of that correlation with other states in the quantum system. In spite of these advantages, little work has been done to understand the ways quantum systems with many states may be used in quantum information processing. At this time we still have no prototypical quantum information processing device. This is due to errors in quantum devices. There are several proposed methods to remedy such errors. These quantum error prevention strategies can be put into three categories, quantum error correcting codes, decoherence-free or noiseless subspaces and dynamical decoupling controls. These methods, and combinations of them, have been applied to the quantum bit (quantum two-state) model of quantum computing. The goal of the proposed project is to develop a model of computation based on higher-dimensional quantum systems, i.e., those with more than two states, and also develop associated quantum error prevention protocols which combine the known methods of error protection. Key components of this project are the educational components which aim to promote discussions as to the best methods of error prevention and to disseminate that knowledge braodly. This will be done in a class and a workshop both of which focus on preventing errors in proposed quantum information processing devices. The class notes and results of the workshop will be published on a web site devoted to quantum error prevention methods. The goal of the research is to overcome the obstacles presented by noisy experiments in order to help develop a prototypical quantum computing device. The impact on science and society could be far-reaching since a quantum computer could solve several important problems more efficiently. In addition to problems in Computer Science, they could simulate quantum mechanical systems far more efficiently than the computers being used today. Such problems are found in Engineering, Chemistry, Biology and Physics. This could lead to better materials, nano-scale devices, pharmaceuticals and better ways in which to extract energy from nuclei.