A New Class of Materials for Quantum Information Processing

Abstract

Abstract : Recent studies show that there exist new classes of states of matter that cannot be described by Landau symmetry breaking theory. String-net condensed states are one of the those new classes of materials, which are even richer than the old symmetry breaking states. After seeing so much impact of symmetry breaking states, one cannot help to imagine the possible applications of the richer string-net condensed states. One possible applications is to use string-net condensed states as media for quantum computing. String-net condensed state is a state with complicated quantum entanglement. As a many-body system, the quantum entanglement in string-net condensed state is distributed among many different particles/spins. As a result, the pattern of quantum entanglements cannot be destroyed by local perturbations. This significantly reduces the effect of decoherence. If we use different quantum entanglements in string-net condensed state to encode quantum information, the quantum information can last for a long time. So we can use string-net condensed state as quantum memory. The quantum information encoded by the string-net entanglements can also be manipulated by dragging the ends of strings around each others. This process realizes quantum computation, or more generally, quantum information processing. It was shown theoretically that certain string-net condensed states can realize arbitrary quantum information processing. So those string-net condensed states are realizations of the universal quantum computer. We see that string-net condensed states are natural media for both quantum memory and quantum computation. Such realizations of quantum memory and quantum computation are naturally fault tolerant.