London, Oct 23 : Scientists have now made it possible to store information inside the nucleus of an atom-a breakthrough that has paved the way for a quantum computer which could crack problems unsolvable by current technology.
Touted as the holy grail of computing, quantum computing involves individual piece of information, or 'bit', which can have more than one value at once, as opposed to current technology which is limited to either 1s or 0s. This can dramatically escalate the processing power and thus widens the scope of what computers can do.
Researchers from Oxford and Princeton universities and Lawrence Berkeley National Laboratory could successfully isolate a quantum bit from a noisy environment to protect the delicate quantum information, while at the same time allowing it to interact with the outside world so that it can be manipulated and measured.
The team's plan was to devise a hybrid system using both the electron and nucleus of an atom of phosphorous embedded in a silicon crystal.
While both the electron and nucleus behave as a tiny quantum magnet capable of storing quantum information, but inside the crystal, the electron is much bigger than the nucleus with an equally stronger magnetic field. This makes the electron well-suited for manipulation and measurement, but not so good for storing information, which can become rapidly corrupted.
Thus, when the information in the electron is ready for storage, it is moved into the nucleus where it can survive for much longer times.
For the experiments, the scientists used silicon enriched with the single 28Si iso-tope, grown by the Berkeley team into large crystals while keeping the material ultra-pure and free from contaminants.
"The electron acts as a middle-man between the nucleus and the outside world. It gives us a way to have our cake and eat it - fast processing speeds from the electron, and long memory times from the nucleus," Nature quoted John Morton, a research fellow at St. John's College, Oxford and lead author of the study, as saying.
They observed that the information stored in the nucleus had a lifetime of about 1 and 3/4 seconds, far more than a recently calculated target for quantum computing in silicon beyond which known error correction techniques could then protect the data for an arbitrarily long period of time.
In the absence of this technique, the researchers could preserve quantum information in silicon as long as a few tens of milliseconds.
"Nobody really knew how long a nucleus might hold quantum information in this system. With the crystals from Lawrence Berkeley and very careful measurements we were delighted to see memory times exceeding the threshold," said Steve Lyon, leader of the Princeton team.
The biggest advantage of the model used in this study is that it is based on silicon technology, which makes it more compatible with today's computers.
The study is published in the latest issue of the journal Nature.