Algorithmic cooling based on cross-relaxation and decoherence-free subspace  

作　　者：Heng Yan Wang Jian Pan Wen Qiang Zheng XinHua Peng 

机构地区：[1]Department of Physics,Zhejiang University of Science and Technology,Hangzhou 310023,China [2]Hefei National Laboratory for Physical Sciences at the Microscale,Department of Modern Physics,University of Science and Technology of China,Hefei 230026,China [3]CAS Key Laboratory of Microscale Magnetic Resonance,University of Science and Technology of China,Hefei 230026,China [4]Synergetic Innovation Center of Quantum Information and Quantum Physics,University of Science and Technology of China,Hefei 230026,China [5]Collaborative Innovation Center for Bio-Med Physics Information Technology,College of Science,Zhejiang University of Technology,Hangzhou 310023,China

出　　处：《Science China(Physics,Mechanics & Astronomy)》2020年第7期47-57,共11页中国科学：物理学、力学、天文学（英文版）

基　　金：supported by the National Key Research and Development Program of China (Grant No. 2018YFA0306600);the National Natural Science Foundation of China (Grant Nos. 11905184, and 11605153);the Natural Science Foundation of Zhejiang Province (Grant No. LQ19A050001);the Anhui Initiative in Quantum Information Technologies (Grant No. AHY050000)

摘　　要：Heat-bath algorithmic cooling(HBAC)has been proven to be a powerful and effective method for obtaining high polarization of the target system.Its cooling upper bound has been recently found using a specific algorithm,the partner pairing algorithm(PPAHBAC).It has been shown that by including cross-relaxation,it is possible to surpass the cooling bounds.Herein,by combining cross-relaxation and decoherence-free subspace,we present a two-qubit reset sequence and then generate a new algorithmic cooling(AC)technique using irreversible polarization compression to further surpass the bound.The proposed two-qubit reset sequence can prepare one of the two qubits to four times the polarization of a single-qubit reset operation in PPA-HBAC for low polarization.When the qubit number is large,the cooling limit of the proposed AC is approximately five times as high as the PPA-HBAC.The results reveal that cross-relaxation and decoherence-free subspace are promising resources to create new AC for higher polarization.

关 键 词：algorithmic cooling polarization enhancing CROSS-RELAXATION decoherence-free subspace 

分 类 号：O413[理学—理论物理] TP301.6[理学—物理]