Missing Link for Quantum Dots Found: Quantum Memory. 
Researchers at the University of Cambridge, St. John’s College, have discovered a method to control electron interaction with nuclear spins.  “Quantum dots are crystals made up of thousands of atoms, and each of these atoms interacts magnetically with the trapped electron.  If left alone to its own devices, this interaction of the electron with the nuclear spins, limits the usefulness of the electron as a quantum bit – a qubit.”  The effort has produced quantum memory storage.

How It Was Done.  In their research, the team exploited the interaction between an electron and thousands of nuclei.  Lasers were used to ‘cool’ the nuclei to less one “thousandth of a degree above the absolute zero temperature.”  Next, the team demonstrated control of nuclei as a single entity, “like a second qubit.”  It is thought the discovery “proves the nuclei in the quantum dot can exchange information with the electron qubit and can be used to store quantum information as a memory device.” 

Showing the quantum coherence of the system is considered the missing link.  “We now have everything needed to build a dedicated quantum memory for every qubit.”  Dr. Gangloff, research lead, explained:

“This is a Holy Grail breakthrough for quantum dot research – both for quantum memory and fundamental research; we now have the tools to study dynamics of complex systems in the spirit of quantum simulation.”

Reference is found at the University of Cambridge, St. Johns College…