This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Quantum computers rely on qubits as their units of information. To connect them into a larger network across long distances, they need to transmit quantum information using light.
Scientists are developing ways to do this using tiny defects in diamond crystals and other semiconductor materials that can act as qubits. However, there is a major problem. Unwanted defects and trapped electrical charges can cause fluctuations that change the frequency of light emitted by the qubits, making it harder to establish reliable quantum connections.
In new research published in the journal Nature, scientists have demonstrated a promising way to get around this instability problem by using a custom-designed molecular system that contains a stable qubit. To create the qubits, a team from German startup NVision Quantum Technologies embedded a chemical compound in a crystal chosen for its ability to provide a stable environment. They then cooled the crystal to 4.5 Kelvin (around -269°C) and used laser light to convert the compound into molecules called carbenes.
Each carbene molecule contains two unpaired electrons whose combined spin can be used to store quantum information. The next step was to see whether they could control and read out the quantum state of an individual molecule. To do this, they used microwave pulses to manipulate the electrons' spin and laser light to read out the results.
They also measured how long the molecules could maintain their quantum states and how stable their light emissions remained over time. And all this work at the molecular scale paid off. The scientists were able to control and read out the spin state of an individual molecule and preserve the spin's delicate quantum properties for around 2.2 milliseconds.
Just as importantly, the frequencies of light emitted by individual molecules remained remarkably stable for more than one hour. "These results establish molecular qubits as a viable platform for single-emitter quantum optics while preserving the advantages of bottom-up chemical design and processable materials," commented the study authors. Of course, this work is only the beginning.
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