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Observation of a ‘‘quantum eraser’’: A revival of coherence in a two-photon interference experiment

Article · July 1992with316 Reads
DOI: 10.1103/PhysRevA.45.7729 · Source: PubMed
We have observed an effect known as a quantum eraser, using a setup similar to one previously employed to demonstrate a violation of Bell's inequalities. In this effect, an interfering system is first rendered incoherent by making the alternate Feynman paths which contribute to the overall process distinguishable; with our apparatus this is achieved by placing a half wave plate in one arm of a Hong-Ou-Mandel interferometer so as to rotate the polarization of the light in that arm by 90°. This adds information to the system, in that polarization is a new parameter which serves to label the path of a given photon, even after a recombining beam splitter. The quantum ``eraser'' removes this information from the state vector, after the output port of the interferometer, but in time to cause interference effects to reappear upon coincidence detection. For this purpose, we use two polarizers in front of our detectors. We present experimental results showing how the degree of erasure (which determines the visibility of the interference) depends on the relative orientation of the polarizers, along with theoretical curves. In addition, we show how this procedure may do more than merely erase, in that the act of ``pasting together'' two previously distinguishable paths can introduce a new relative phase between them.
  • ...This cannot be explained as interference of wavepackets in ordinary space. And there are by now many other photon-correlation experiments that point in the same direction[94],[189],[190]. In fact, spacelike correlations between photons (length of the order of 30 µm) entangled over more than 10 km[191],[192], 16 km[103], and 143 km[193]have been observed[194]. ...
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  • ...The modern view of wave-particle duality has opened new research avenues, for example in the development of novel measurement schemes, as the ones based on quantum non-demolition [20]. The traditional quantum eraser experiment [21][22][23][24][25][26][27][28][29], and its delayed choice versions [29][30][31][32] are related to the complementarity principle formulated by Bohr in 1928 [33], which states that photons can behave indistinctly as particles or waves but cannot be observed as both simultaneously. Importantly, the double-slit experiment and its modern variations allows to link the which-way information provided by the whole system with the interference pattern produced at the detection plane [34]. ...
  • ...Depending upon the thickness of the phase shifter, the interference observed at detectors D1 and D2 can be constructive, destructive, or intermediate. Observing interference at the detectors D1 and D2 can be interpreted in terms of not having "which-path" information (WPI) about the single photon [13][14][15][16][17][18]. WPI is a common term associated with these types of experiments and was popularized by Wheeler [22]. ...
  • ...It shows the interference of two identical photons (bosons) at a 50:50 beam splitter where the chances of observing coincidence counts in the output ports depends on the symmetry of the two-photon state. HOM interference has been investigated for many scenarios, for example, in polarization [16], path length [17], and the radial dependence of the light field in a transversal plane [18], as well as in spectral filtering [19], for different single-photon sources [20] and with spatial modes [21][22][23][24]. Generalizations to higher photon numbers and multiports, as well as realizations with other bosonic systems [25], have been discussed in the literature. ...
  • ...In recent years state pre-selection and post-selection (PPS) techniques have been used to manipulate and control quantum systems (e.g. [1][2][3][4]). An important closely related area of PPS research has focused upon the study of weak values of quantum mechanical observables (e.g. ...
  • ...Englert, in his paper [1] showed that, the derivation of the complimentary relation between distinguishibility and visibility is logically independent of any uncertainty principle and relies solely on unitary transformation of the system and the entangled meter state. Englert's analysis can also be included in the discussion of Quantum erasure [2][4] . Quantum erasure is a particular technique to protect the interference fringe pattern in an interference experiment, at the expanse of the respective complimentary knowledge of " which way information " . ...
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