Interference of Bose-Einstein condensates: Quantum nonlocal effects

Nonlocal quantum effects with Bose-Einstein condensates.

We study theoretically the properties of two Bose-Einstein condensates in different spin states, represented by a double Fock state. Individual measurements of the spins of the particles are performed in transverse directions, giving access to the relative phase of the condensates. Initially, this phase is completely undefined, and the first measurements provide random results. But a fixed valu...

Beyond spontaneously broken symmetry in Bose-Einstein condensates.

Spontaneous symmetry breaking (SSB) for Bose-Einstein condensates cannot treat phase off-diagonal effects, and thus cannot explain Bell inequality violations. We describe another situation that is beyond a SSB treatment: an experiment where particles from two (possibly macroscopic) condensate sources are used for conjugate measurements of the relative phase and populations. Off-diagonal phase e...

Evolution of additional (hidden) quantum variables in the interference of Bose-Einstein condensates

Quantum Computation using Two Component Bose-Einstein Condensates

Quantum computation using qubits made of two component Bose-Einstein condensates (BECs) is analyzed. We construct a general framework for quantum algorithms to be executed using the collective states of the BECs. The use of BECs allows for an increase of energy scales via bosonic enhancement, resulting in two qubit gate operations that can be performed at a time reduced by a factor of N , where...

Number Fluctuations and Phase Diffusion in a Bose-Einstein Condensate of Light

Bose-Einstein condensates of quasiparticles such as exciton-polaritons, magnons and massive photons allow for new experimental possibilities as compared to the atomic Bose-Einstein condensates. In this Thesis we focus on a condensate of photons, first created at Bonn University in 2010. One of the recent achievements is the measurement of number fluctuations in such a condensate of photons. We ...