The Hanbury Brown and Twiss experiment with fermions

Abstract

We realized an equivalent Hanbury Brown and Twiss experiment for a beam of electrons in a two dimensional electron gas in the quantum Hall regime. A metallic split gate serves as a tunable beam splitter which is used to partition the incident beam into transmitted and reflected partial beams. The current fluctuations in the reflected and transmitted beam are fully anticorrelated demonstrating that fermions tend to exclude each other (antibunching). If the occupation probability of the incident beam is lowered by an additional gate, the anticorrelation is reduced and disappears in the classical limit of a highly diluted beam. Keywords: quantum statistics; noise; correlationThe first quantum statistical measurements were carried out with photons by Hanbury Brown and Twiss (HBT) in the 1950s. In a pioneering experiment HBT determined the size of astronomical radio sources by measuring the spatial coherence of the emitted radiation from correlations between intensity fluctuations at two different locations [1]. In a subsequent optical table-top experiment, they tested their idea by measuring intensity correlations for visible light: the light beam of a Hg vapor lamp (IN) was split into a transmitted (T) and a reflected beam (R) (see Fig. 1). The equal-time intensity correlations between the two separated photon streams was found to be positive (bunching) [2,3]. This is a generic property of particles 1 To whom correspondence should be addressed: E-mail: stefan.oberholzer@unibas.ch obeying Bose-Einstein statistics. In contrast to bosons, a negative correlation or 'antibunching' is expected for fermions, because fermions have to exclude each other due to the Pauli principle.In general, the time dependent number of particles n(t) detected during a certain time interval exhibits fluctuations ∆n(t) = n(t) − n around the average n , called shot noise. Shot noise in the electrical current is caused by the discreteness of the electron charge and has been extensively studied in submicrometer-sized nanostructures [4,5]. In a HBT type experiment, not the fluctuations in a single beam are measured, but the correlation between fluctuations in the transmitted (T) and reflected (R) beam originating from a beam splitter (see Fig. 1). If the incident beam (IN) is not prepared at a single-particle level, but shows intensity

Positive cross-correlations due to dynamical channel blockade in a three-terminal quantum dot

“…Oberholzer et al have shown how the cross correlations vanish in the classical limit. 9 Up to now, positive cross correlations have never been measured in electronic circuits. However, nothing forbids to reverse the sign of cross correlations if a hypothesis of Büt-tiker's proof is not fulfilled (see Ref.…”

Effect of incoherent scattering on shot noise correlations in the quantum Hall regime

“…Recently, Hanbury Brown and Twiss (HBT) experiments studying current correlations using partially degenerate stream of fermions were performed [9,10], starting from the idea [11] of using the edge states in a conductor submitted to a strong magnetic field. A Y-structure is discussed in Ref.…”

Positive Current Correlations Associated with Super-Poissonian Shot Noise

“…(1) has been tested only for ideal tunnel barriers [14,15], where the transport mechanism is direct tunneling with a probability of T. This stochastic process leads to a shot noise of S I 2eI1 ÿ T in the tunneling current. The Fano factor of such a barrier is then F S I =2eI 1 ÿ T. Equation (1) can thus be rewritten in the following form, for ideal tunnel barriers:…”