Neutrons in a time-dependent magnetic field: Photon exchange and decoherence modeling

Abstract

If a quantum mechanical particle passes a spatially finite region of a purely time-dependent potential, coherent emission and absorption of energy take place. Due to Zeeman interaction, this situation can be realized with neutrons crossing an oscillating magnetic field. We solve the corresponding Schrödinger equation for fields consisting of an arbitrary number of frequencies and measure the calculated transition amplitudes for the quantized energy transfer by means of time-dependent neutron interferometry. Investigating the interferometer contrast for magnetic signals consisting of a high number of modes whose phases are randomly distributed shows that noise fields and therefore decoherence processes can be modeled in this calculation as well.

Metaoptics with Nonrelativistic Matter Waves

“…At τ = τ 1 , the abscissas of the "+" and "−" wave packets are such that x + < x − , then their mutual longitudinal separation Δ L x monotonously increases with t or x, which cancels any interference effect between them (once remixed), in other words a total loss of contrast as the distance to the detector is increased. Figure 3 A similar phenomenon is described in [18] for the case of neutron interferometry. In principle it is possible to recover the contrast via the action of a second reversed comoving pulse provided that the characteristics of this second pulse (especially its duration τ 1 ) are adjusted such that the final velocities are exactly equal to each other.…”

“…In place of a static field profile, a comoving field can be used as well, as it has been demonstrated in [6] [18]. The magnetic potential they use is a sum of terms of the form C(x)V k cos(ω k t + ϕ k ), where C(x) is a square function of a definite width L and V k , ω k , ϕ k are constants.…”

Photon exchange and entanglement formation during transmission through a rectangular quantum barrier

“…In that case, standard methods for differential equations suffice to find the solution [26,27] . If we assume the wave function in region I to be a plane wave with wave vector we get for the wave function behind the potential barrier where For a more detailed derivation including the solution for region II as well we refer to [26,28] .…”

“…For a more detailed derivation including the solution for region II as well we refer to [21,23]. In summary, a plane wave |k 0 gets split up into a coherent superposition of plane waves |k n whose energy is given by the incident energy E 0 plus integer multiples of ω.…”

Quantum decoherence by Coulomb interaction

“…the emission of photons out of Rydberg atoms in a microwave cavity [27] or out of helium atoms after interacting with a standing light wave [28]. Also, decoherence studies with neutron matter waves crossing oscillating magnetic fields have been conducted [29,30]. Matter wave interferometers are in particular suitable for such experiments, where decoherent interactions lead to a gradually leakage of which-path information and a deteriorating fringe contrast.…”