Quantum control and information processing

Go Kato

Quantum information processing will enable us to solve problems that conventional computers cannot or provide informationally secure cryptography.However, there are still difficulties in achieving quantum information processing.This article introduces indirect quantum control as one method to overcome these difficulties and shows that indirect quantum control has excellent properties for achieving quantum information processing.

Paul W. Brumer, Daniel A. Lidar, H-K Lo +1 more

Hao Zhang, Xue-Ke Song, Qing Ai +3 more

Adiabatic quantum control is a very important approach for quantum physics and quantum information processing (QIP). It holds the advantage with robustness to experimental imperfections but accumulates more decoherence due to the long evolution time. Here, we propose a universal protocol for fast and robust quantum control in multimode interactions of a quantum system by using shortcuts to adiabaticity. The results show this protocol can speed up the evolution of a multimode quantum system effectively, and it can also keep the robustness very good while adiabatic quantum control processes cannot. We apply this protocol for the quantum state transfer in QIP in the photon-phonon interactions in an optomechanical system, showing a perfect result. These good features make this protocol have the capability of improving effectively the feasibility of the practical applications of multimode interactions in QIP in experiment.

Peter J. Pemberton-Ross, Sonia G. Schirmer, I. C. H. Pullen

PNG WEN HAN

Nicolas Boulant, Shunsuke Furuta, Joseph Emerson +2 more

We explore in this paper incoherent processes, which can be modelled as a distribution of unitary processes corresponding to spatially or slowly varying control parameters. Incoherent processes are an important source of errors in quantum information processing. These processes also cause problems and ambiguities for quantum process tomography for which we give examples to illustrate the issues. In an effort to characterize these processes, we develop methods of analysis based on the eigenvalue spectra of superoperators to extract information about the noise source. Examples from nuclear magnetic resonance are provided to illustrate the utility of such information in designing control sequences that directly counteract incoherent noise.