Storing information in a quantum memory system is a difficult challenge, as the data is usually quickly lost. At TU Wien, Austria, ultra-long storage times have now been achieved using tiny diamonds.
By storing information in a quantum memory system with quantum particles, information can be stored and manipulated – this is the basis of many very promising technologies, such as extremely sensitive quantum sensors, quantum communication or even quantum computers.
However, there is a significant problem, it is difficult to store information in a quantum physical system for a long period of time. The quantum information tends to dissipate within fractions of a second due to interactions with the environment.
Results from the research at TU Wien published in the journal Nature Materials suggest it has now been possible to store information for hours at a time using special diamonds. This makes quantum information even more stable than the conventional information stored in the working memory of computers.
How have the diamonds helped to achieve memory storing?
Johannes Majer, Research Group Leader at the Institute of Atomic and Subatomic Physics at TU Wien said: “We are using tiny diamonds intentionally seeded with small defects.” Normally a diamond is composed only of carbon atoms. By irradiating the diamond, it is possible to introduce a nitrogen atom into the diamond structure in place of a carbon atom at certain points, which then leaves an unoccupied point in the crystal lattice next to it.
This “lattice defect” is known as an NV- centre or nitrogen-vacancy centre. The nitrogen atom and the empty site can assume different states, so this lattice defect site can be used to store an information quantum bit.
For the first time, scientists at the Institute of Atomic and Subatomic Physics at TU Wien have now been able to experimentally determine the characteristic period, during which the diamond errors lose their quantum information.
The measurements were carried out at very low temperatures, just above the absolute zero temperature, at 20 millikelvins. Heat would disturb the system environment and erase the quantum information. It became apparent that the diamonds can store their information over several hours, much longer than was thought possible.
Majer added: “The information in the D-RAM chip of an ordinary computer memory is much less stable. There the energy is lost within a few hundred milliseconds, meaning that the information then has to be refreshed,”
Not all diamonds with defects offer the same storage periods, the phenomenon was investigated thoroughly using computer simulations. Johannes Gugler and Professor Peter Mohn,TU Wien, carried out complex calculations that led to the explanation that the extraordinary stability of diamond quantum memory storage is due to the particularly stiff diamond lattice allowing the new quantum memory storage to retain information for longer periods.