Wave–particle duality, as manifest in the two-slit experiment, provides perhaps the most vivid illustration of Bohr's complementarity principle: wave-like behaviour (interference) occurs only when the different possible paths a particle can take are indistinguishable, even in principle1. The introduction of a which-path (welcher Weg) detector for determining the actual path taken by the particle inevitably involved coupling the particle to a measuring environment, which in turn results in dephasing (suppression of interference). In other words, simultaneous observations of wave and particle behaviour is prohibited. Such a manifestation of the complementarity principle was demonstrated recently using a pair of correlated photons, with measurement of one photon being used to determine the path taken by the other and so prevent single-photon interference2. Here we report the dephasing effects of a which-path detector on electrons traversing a double-path interferometer. We find that by varying the sensitivity of the detector we can affect the visibility of the oscillatory interference signal, thereby verifying the complementarity principle for fermions.
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Bohr, N. in Albert Einstein: Philosopher—Scientist (ed. Schilpp, P. A.) 200–241 (Library of Living Philosophers, Evanston, 1949).
Zou, X. Y., Wang, L. J. & Mandel, L. Induced coherence and indistinguishability in optical interference. Phys. Rev. Lett. 67, 318–321 (1991).
Imry, Y. Introduction to Mesoscopic Physics (Oxford Univ. Press, 1997).
Stern, A., Aharonov, Y. & Imry, Y. Phase uncertainty and loss of interference: a general picture. Phys. Rev. A 41, 3436–3448 (1990).
Schuster, R.et al. Phase measurement in a quantum dot via a double-slit interference experiment. Nature 385, 417–420 (1997).
Van Houten, H., Beenakker, C. W. J. & Staring, A. A. W. in Single Charge Tunneling—Coulomb Blockade Phenomena in Nanostructures (eds Grabert, H. & Devoret, M. H.) Ch. 5 (Plenum, New York, 1992).
Gurvitz, S. A. Interaction free measurement in mesoscopic systems and the reduction postulate.Preprint available at http://xxx.lanl.gov/abs/quant-ph/9607029.
Field, M.et al. Measurements of Coulomb blockade with a noninvasive voltage probe. Phys. Rev. Lett. 70, 1311–1314 (1993).
Buttiker, M. Four terminal phase coherent conductance. Phys. Rev. Lett. 57, 1761–1764 (1986).
Aronov, A. G. & Sharvin, Yu. V. Magnetic flux effects in disordered conductors. Rev. Mod. Phys. 59, 755–779 (1987).
Aleiner, I. L., Wingreen, N. S. & Meir, Y. Dephasing and the orthogonality catastrophe in tunneling through a quantum dot: the “which path?” interferometer. Phys. Rev. Lett. 79, 3740–3743 (1997).
Levinson, Y. Dephasing in a quantum dot due to coupling with a quantum point contact. Europhys. Lett. 39, 299–304 (1997).
Gurvitz, S. A. Measurements with a noninvasive detector and dephasing mechanism. Phys. Rev. B 56, 15215–15223 (1997).
Imry, Y. in Proc. 1997 Nobel Symp. on Modern Studies of Basic Quantum Concepts and Phenomena (in the press).
Eglert, B. G. Fringe visibility and which-way information: an inequality. Phys. Rev. Lett. 77, 2154–2157 (1996).
Khlus, V. A. Current and voltage fluctuations in microjunctions between normal metals and superconductors. JETP 66, 1243–1249 (1987).
Lesovik, G. B. Excess quantum noise in 2D ballistic point contacts. JETP Lett. 49, 592–594 (1989).
We thank S. Gurvitz for presenting to us ref. 7, which initiated the present work. We also thank I. Imry, Y. Levinson, Y. Meir, A. Stern and N. Wingreen for discussions. This work was supported in part by a MINERVA grant and a MINERVA fellowship for one of us (R.S.).
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Buks, E., Schuster, R., Heiblum, M. et al. Dephasing in electron interference by a ‘which-path’ detector. Nature 391, 871–874 (1998). https://doi.org/10.1038/36057