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Paper 1
Avoiding coherent errors with rotated concatenated stabilizer codes
Yingkai Ouyang
- Year
- 2020
- Journal
- arXiv preprint
- DOI
- arXiv:2010.00538
- arXiv
- 2010.00538
Coherent errors, which arise from collective couplings, are a dominant form of noise in many realistic quantum systems, and are more damaging than oft considered stochastic errors. Here, we propose integrating stabilizer codes with constant-excitation codes by code concatenation. Namely, by concatenating an $[[n,k,d]]$ stabilizer outer code with dual-rail inner codes, we obtain a $[[2n,k,d]]$ constant-excitation code immune from coherent phase errors and also equivalent to a Pauli-rotated stabilizer code. When the stabilizer outer code is fault-tolerant, the constant-excitation code has a positive fault-tolerant threshold against stochastic errors. Setting the outer code as a four-qubit amplitude damping code yields an eight-qubit constant-excitation code that corrects a single amplitude damping error, and we analyze this code's potential as a quantum memory.
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M Times Photon Subtraction-Addition Coherent Superposition Operated Odd-Schrődinger-cat State: Nonclassicality and Decoherence
Li Huang, Qin Guo, Li-ying Jiang, Ge Chen, Xue-xiang Xu, Wen Yuan
- Year
- 2014
- Journal
- arXiv preprint
- DOI
- arXiv:1407.7104
- arXiv
- 1407.7104
We introduce a new non-Gaussian state, generated by m times coherent superposition operation $a\cos θ+a^{\dagger }e^{i\varphi }\sin θ$ (MCSO) on odd-Schrodinger-cat state (OSCS). Its normalized constant is turned out to be related with the Hermite polynomial. We further investigate the nonclassical properties of the MCSO-OSCS through Mandel's Q-parameter, quadrature squeezing, the photocount distribution and Wigner function (WF). It is shown that the nonclassicality of the MCSO-OSCS is influenced by the number of times (m) of coherent superpositon operation, the angle $θ$ and the amplitude of the coherent state (|$α_{0}$|). Especially the volume of negative region of WF increases with the increment of parameters m, $θ$ and $α_{0}$. We also investigate the decoherence of the MCSO-OSCS in terms of the fadeaway of the negativity of WF in a thermal environment.
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