A single-electron two-path interference (Young) experiment is considered theoretically. The decoherence of an electron wave packet due to the which path trace left in a conducting (metallic) plate placed under the electron trajectories is calculated using the many-body quantum description of the electron gas reservoir.
The problem of quantum interference in the presence of an environment is considered by two approaches. One treats the problem from the point of view of the trace left by the interfering particle on its environment. The other regards the phase accumulation of the interfering waves as a statistical process, and explains the loss of interference in terms of uncertainty in the relative phase. The equivalence of the two approaches is proven for the general case. The two approaches are applied to dephasing of electron interference by photon modes in coherent and thermal states, and to dephasing by electromagnetic fluctuations in metals.
Controlled decoherence of free electrons due to Coulomb interaction with a truly macroscopic environment, the electron (and phonon) gas inside a semiconducting plate, is studied experimentally. The quantitative results are compared with different theoretical models. The experiment confirms the main features of the theory of decoherence and can be interpreted in terms of which-path information. In contrast to previous model experiments on decoherence, the obtained interferograms directly visualize the transition from quantum to classical.
Abstract In Copenhagen’s interpretation, a self-interference mechanism is assumed for a wave function to split and to pass through the slits simultaneously, then recombine and collapse to generate a dot signal on a detector. Its use of a single wave function to describe a whole ensemble without accounting for a particle’s individuality is incomplete. To better understand the single-electron double-slit interference, we use a wave-packet trajectory approach to track each electron’s dynamics and calculate the time-dependent interference intensity. We analyze the self-interference and cross-interference mechanisms to illustrate how an electron’s coherence length affects the self-interference and how it dictates the wave packet overlaps between adjacent electrons for the cross-interference mechanism to be effective. To circumvent a conflicting dilemma between the electron’s indivisibility and its wave-packet split while passing through the slits, we consider an alternate mechanism involving slit-induced quantized momentum. This mechanism preserves the electron’s indivisibility and avoids the illusive split, recombination and mysterious collapse of a single particle’s wave function.
A controlled decoherence environment is studied experimentally by free electron interaction with semiconducting and metallic plates. The results are compared with physical models based on decoherence theory to investigate the quantum-classical transition. The experiment is consistent with decoherence theory and rules out established Coulomb interaction models in favor of plasmonic excitation models. In contrast to previous decoherence experiments, the present experiment is sensitive to the onset of decoherence.
An experiment in which decoherence, i.e. the transition from quantum to classical behaviour, can be studied in detail was proposed by Anglin and Zurek [1] and has now been realized. An electron beam in a biprism interferometer is split into two parts both of which travel over a plate made of a highly resistive material at the same, small height. The induced charges inside the plate move along with the beam electron, therefore a current results which encounters ohmic resistance. This process leads to a disturbance in the electron and phonon gas in the plate. As this disturbance is different for the two parts of the beam, entanglement between beam electron and plate is formed. The strength of decoherence, represented by the visibility of the interference fringes, varies as a function of two parameters, the height above the plate and the lateral separation of the beams. Allowing electrons of different height to reach the fluorescent screen successively, 'photos' of the quantum-classical border (continuous decrease of contrast with decreasing height above the plate) are built up.