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Observation of Hanbury Brown–Twiss anticorrelations for free electrons


Fluctuations in the counting rate of photons originating from uncorrelated point sources become, within the coherently illuminated area, slightly enhanced compared to a random sequence of classical particles. This phenomenon, known in astronomy as the Hanbury Brown–Twiss effect1,2,3,4,5, is a consequence of quantum interference between two indistinguishable photons and Bose–Einstein statistics6. The latter require that the composite bosonic wavefunction is a symmetric superposition of the two possible paths. For fermions, the corresponding two-particle wavefunction is antisymmetric: this excludes overlapping wave trains, which are forbidden by the Pauli exclusion principle. Here we use an electron field emitter to coherently illuminate two detectors, and find anticorrelations in the arrival times of the free electrons. The particle beam has low degeneracy (about 10-4 electrons per cell in phase space); as such, our experiment represents the fermionic twin of the Hanbury Brown–Twiss effect for photons.

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Figure 1: Electron optical set-up (top) and fast coincidence electronics (bottom) to measure electron anticorrelations.
Figure 2: Schematic time spectra expected for poissonian processes at infinite time resolution (straight lines) and an antibunched beam at finite resolving time in semilogarithmic representation.
Figure 3: Antibunching as a function of coherence of illumination of the collectors.


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We thank M. Silverman, M. Lenc, T. Tyc, A. Oed and P. Sonnentag for discussions, and the Deutsche Forschungsgemeinschaft for financial support.

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Correspondence to Franz Hasselbach.

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Kiesel, H., Renz, A. & Hasselbach, F. Observation of Hanbury Brown–Twiss anticorrelations for free electrons. Nature 418, 392–394 (2002).

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