We argue that the modification proposed by Li et al. [Chin. Phys. Lett. 32 （2015）050303] to the experiment of Danan et al. [Phys. Rev. Lett. 111 （2013） 240402] does not test the past of the photon as characterized...We argue that the modification proposed by Li et al. [Chin. Phys. Lett. 32 （2015）050303] to the experiment of Danan et al. [Phys. Rev. Lett. 111 （2013） 240402] does not test the past of the photon as characterized by local weak traces. Instead of answering the questions： （i） were the photons in A？ （ii） were the photons in B？ and （iii） were the photons in C？ the proposed experiment measures a degenerate operator answering the questions： （i） were the photons in A？ and （ii） were the photons in B and C together？ A negative answer to the last question does not tell us if photons were present in B or C. On the other hand, a simple variation of the proposal by Li et al. does provide conceptually better evidence for the past of the pre- and post-selected photon, but this evidence will be in agreement with the results of Danan et al.展开更多
基金Supported by the German-Israeli Foundation for Scientific Research and Development under Grant No I-1275-303.14
文摘We argue that the modification proposed by Li et al. [Chin. Phys. Lett. 32 （2015）050303] to the experiment of Danan et al. [Phys. Rev. Lett. 111 （2013） 240402] does not test the past of the photon as characterized by local weak traces. Instead of answering the questions： （i） were the photons in A？ （ii） were the photons in B？ and （iii） were the photons in C？ the proposed experiment measures a degenerate operator answering the questions： （i） were the photons in A？ and （ii） were the photons in B and C together？ A negative answer to the last question does not tell us if photons were present in B or C. On the other hand, a simple variation of the proposal by Li et al. does provide conceptually better evidence for the past of the pre- and post-selected photon, but this evidence will be in agreement with the results of Danan et al.
