Physicists are exploring the construction of quantum memory that can store and retrieve quantum data efficiently.
If you thought the measurement of quantum information that involves an observer was difficult or confusing, storing the information is a whole other story.
If we want efficient quantum systems that can address our current and future computational problems, we have to be able to not only measure, but also store and retrieve photonic quantum information at will.
For that, we need quantum memory, and this is an exotic piece of theoretical hardware that’s proving to be hard to build.
No Quantum Computing Without Quantum Memory
Just like their silicon-based counterparts need RAM to function, quantum computers will need memory to read and write data, and accomplish all the tasks expected of them.
While memory devices are based on a tried-and-tested concept with traditional computers, in the case of quantum computers, it is much more challenging.
The difficulty of creating a quantum memory comes from the problem of quantum decoherence.
As volatile as it is, quantum data tend to get altered, or may even disappear altogether, as soon as we attempt to intervene to process it.
From an engineering perspective, qubits are so sensitive that the slightest noise (vibrations) from nearby particles could compromise the memory’s ability to store data.
Until now, engineers have been able to bypass the issue of decoherence and silence atoms’ noise by cooling the whole system to extremely low temperatures.
D-Wave quantum systems, which are currently the industry’s best, require a gelid environment with temperature nearing -460° F, which is about 180 times colder than outer space.
For future quantum computers and large-scale quantum networks, scientists need to develop more practical solutions.
Quantum memory interfaces have to function at room temperature, and that’s one of the biggest hurdles physicists need to clear.
Diamond Strings and 3D Cavities for Quantum Memory Devices
Last month, an international team of physicists presented their concept of a new type of quantum memory device based on diamond.
To circumvent decoherence barrier, researchers say that quantum memory made of guitar-like diamond strings can store qubits and keep them stable.
Using diamond for storing quantum data is a concept that’s been explored for many years now.
Another research team from three universities in Germany – Walther-Meissner-Institut, Technical University of Munich, and Nanosystems Initiative Munich – has been working on a 3D quantum memory device.
The concept 3D device uses microwave waveguide cavities to keep qubits stable for as long as possible to offer long coherence times – up to few milliseconds.
“Since quantum information is very fragile, it needs to be processed fast or preserved in a suitable storage. These two requirements are typically conflicting. The greatest significance of our work is that it shows how to build a device with fast access to stored quantum information, enabling fast processing, combined with a long storage time,” Edwar Xie, lead author of the paper told Phys.org.
Tunable diamond strings and 3D-cavities devices are two among other potential solutions to the storage and processing of quantum information that still have to prove their large-scale viability.