Researchers have been able to achieve quantum coherence at room temperature – this is the ability of a quantum system to maintain a well-defined state without being affected by external disturbances. This breakthrough is an important step forward in the development of quantum computers. It is easier to work with them if you do not have to cool them down to incredibly low temperatures.
Quantum computers’ fundamental unit of information is the qubit. These tend to be made of a few particles entangled in a specific state. That means that no matter the distance you put between them, any interaction with one of them affects all the particles in the state. This is extremely useful for the computation side of things, but an entangled state is also very fragile.
In this work, the team achieved an entangled quintet state in electrons. They were able to craft it by using a chromophore – a dye molecule that absorbs light and emits a specific wavelength (or color), making it perfect to excite electrons in a specific way to get to the singlet. But that alone is not enough. The chromophore was embedded in a metal-organic framework (MOF), which is a nanoporous crystalline material.
The MOF was chosen to accumulate a lot of chromophores, but keep them restricted in their angle of motion. They are able to move sufficiently that as they emit color they excite electrons in the quintet state, but the motion restrictions suppress the shaking that would lead to a breakdown of the state.
“This is the first room-temperature quantum coherence of entangled quintets,” co-author Professor Yasuhiro Kobori of Kobe University said in a statement.
The team was able to use microwave light to check the state of the system, showing it remained in quantum coherence for over 100 nanoseconds. This is a tiny fraction of a second, but it shows that quantum coherence is achievable at room temperature.
“It will be possible to generate quintet multiexciton state qubits more efficiently in the future by searching for guest molecules that can induce more such suppressed motions and by developing suitable MOF structures,” speculates senior author Associate Professor Nobuhiro Yanai from Kyushu University. “This can open doors to room-temperature molecular quantum computing based on multiple quantum gate control and quantum sensing of various target compounds.”
Quantum sensing is a particularly exciting application. By using the extremely sensitive nature of quantum entanglement (which is usually the problem), researchers believe they can develop sensing technologies with higher resolutions and sensitivities compared to the ones currently in use.
The study is published in Science Advances.