Quantum Solid-State Physics

Yosuke Nagaoka

Andrew M. Steane

In their article "Solid start for solid-state quantum bits" (July pp2l–22), Caspar van der Wal and Leo Kouwenhoven report an excellent experiment in solid-state physics by Yasunoba Nakamura and colleagues (Nature 398 786). Both the original paper in Nature and the article about this paper in Physics World are examples of good research, carefully explained. However, I believe this work has been misrepresented by the editors of Physics World and by Nature.

Gabriele De Chiara, Časlav Brukner, Rosario Fazio +2 more

Some thermodynamical properties of solids, such as heat capacity and magnetic susceptibility, have recently been shown to be linked to the amount of entanglement in a solid. However, this entanglement may appear a mere mathematical artefact of the typical symmetrization procedure of many-body wavefunction in solid state physics. Here we show that this entanglement is physical, demonstrating the principles of its extraction from a typical solid-state system by scattering two particles off the system. Moreover, we show how to simulate this process using present day optical lattice technology. This demonstrates not only that entanglement exists in solids but also that it can be used for quantum information processing or as a test of Bell's inequalities.