Simulation of interaction Hamiltonians by quantum feedback: a comment on the dynamics of information exchange between coupled systems

Comment on Photon Exchange Interactions

We previously suggested that photon exchange interactions could be used to produce nonlinear effects at the two-photon level, and similar effects have been experimentally observed by Resch et al. (quant-ph/0306198). Here we note that photon exchange interactions are not useful for quantum information processing because they require the presence of substantial photon loss. This dependence on loss is somewhat analogous to the postselection required in the linear optics approach to quantum computing suggested by Knill, Laflamme, and Milburn [Nature 409, 46 (2001)].

Comment on "Excitons in Molecular Aggregates with Levy Disorder: Anomalous Localization and Exchange Broadening of Optical Spectra"

In their Letter [Phys. Rev. Lett. 105, 137402 (2010)], Eisfeld et al. predicted the exchange broadening and blue-shift of the absorption band as well as a nonuniversal disorder scaling of the localization length of excitons in J-aggregates with Levy disorder, which they contrasted with the previously analyzed Gaussian and Lorentzian case [Phys. Rev. B, 79, 1 (2009)]. The observations were explained by chain segmentation due to outliers, and its interplay with localization of states in effective potential wells created by typical random site energies. We argue that the previously known theory d…

Comment on ``Creating Metastable Schroedinger Cat States''

After a careful analysis of the feedback model recently proposed by Slosser and Milburn [Phys. Rev. Lett. 75, 418 (1995)], we are led to the conclusion that---under realistic conditions---their scheme is not significantly more effective in the production of linear superpositions of macroscopically distinguishable quantum states than the usual quantum-optical Kerr effect.

Comment on "New Scaling of Child-Langmuir Law in the Quantum Regime"

In their letter on the quantum Child-Langmuir law, Ang, Kwan and Lau (Phys. Rev. Lett. 91, 208303 (2003)) include exchange correlation effects within the Kohn-Sham density functional theory and explore numerically the maximum transmitted current in nanogaps. We show here that the calculations are in error as the exchange-correlation component of the chemical potential has been ignored while fixing the boundary conditions for the Hartree potential.

关于量子环境不变性和交换对称性的统计力学评论

Comment on Statistical mechanics from quantum envariance and exchange symmetry

本文评论了Ojha等人关于统计力学的观点，指出其结论不成立，如约化密度矩阵有误、熵条件不满足等，通过双粒子计算显化矛盾，还指出萨哈部分问题，给出修正公式并确定不受影响的结果。

连续测量与反馈下耗散量子比特与监测器之间的能量交换与涨落

Energy exchange and fluctuations between a dissipative qubit and a monitor under continuous measurement and feedback

本文利用Lindblad方程研究连续测量与反馈下耗散量子比特和监测器间的稳态能量流及其涨落，揭示测量反作用诱导的冷却效应和非泊松涨落特性，为量子制冷机设计提供新思路。