Remote Entanglement of Trapped Ions and Loophole-Free Bell Inequality

University Of Washington, Seattle WA

Investigators

Abstract

The main goal of this project is to study quantum entanglement, which is arguably the most perplexing feature of the already confusing theory of quantum mechanics. Quantum mechanics, the theory that describes the microscopic world--elementary particles, atoms, molecules, photons and so on--allows particles to be at many places at the same time, a property called superposition. If several particles are in a superposition state, then their individual properties may become "entangled" in such a way that detecting one of the particles will affect the other particles even though there is no direct physical connection between them. Dubbed "spooky action at a distance" by Albert Einstein, this property has no classical physics analog, and its understanding is essential for verifying the validity of quantum mechanics. This seemingly esoteric property also has important practical applications and implications for a rapidly developing new technology: quantum computation and quantum communication. Quantum computers should be able to break computational speed records using exotic algorithms; their very existence requires strong quantum entanglement between the quantum bits, or "qubits", which form the basis of their operation. Quantum communication channels can transmit data with the highest possible levels of security; the reliability and range of these channels depends crucially on the ability to generate entanglement. The PI's will use trapped Ba ion qubits and the ion-photon entanglement protocol to generate long distance entanglement between the ions. The long (~1 km) range is needed to close both the locality loophole (which requires the measurements on the two qubits to be outside of each other's light cone) and the detection, or fair sampling, loophole (which requires that the detection efficiency is high) in the same experiment. The photons emitted by the ions will be sent though optical fibers and measured in a partial Bell state analyzer, a process which in turn entangles the distant ions via entanglement swapping.