Confirmation of this elusive state in quantum systems could lead to more efficient quantum devices.
Quantum computers have the potential to revolutionize technology by solving complex calculations and computations that are difficult, if not impossible, for traditional computers. One major roadblock, however, is instability-quantum states can be easily disrupted by "noise" from their surrounding environments, causing errors in the systems. Overcoming instability is important in creating effective and reliable quantum computers and other quantum technologies.
Researchers at the University of Rochester-including John Nichol, an associate professor in the Department of Physics and Astronomy-have taken a key step toward reducing instability in quantum systems, by focusing on an elusive state called a nuclear-spin dark state. Although scientists have long suspected that the nuclear-spin dark state could exist, they haven't been able to provide direct evidence of it-until now.
"By directly confirming the existence of the dark state and its properties, the findings not only validate decades of theoretical predictions but also open the door to developing more advanced quantum systems," Nichol says.
The research, published in Nature Physics, focuses on using quantum dots-tiny semiconductor particles that trap single electrons and use their "spin" to store information-to create a nuclear-spin dark state.
What is nuclear-spin dark state?
A nuclear-spin dark state is a special quantum state where the nucleus of an atom becomes, in essence, "hidden" from the outside world. In a nuclear-spin dark state, the tiny magnetic properties-known as spins-of atomic nuclei line up and synchronize in a way that stops them from disturbing an electron's spin. This helps to keep the electron spin stable.
Imagine an electron's spin is a soloist trying to perform, while the surrounding atomic nuclei are like an orchestra. If the musicians in the orchestra are out of sync, playing at different speeds and volumes, it can throw off the soloist. But if the orchestra members align their timing and play perfectly in sync, their sound can blend into the background, and the soloist's music will be clear and undisturbed.
Harnessing dark states for quantum technologies
Nichol and his colleagues used a technique called dynamic nuclear polarization to align the nuclear spins, creating conditions for the nuclear-spin dark state to form. They directly measured its effects and found that the dark state significantly reduced interactions between the spins of electrons and nuclei.
The research has many potential applications in quantum sensing and quantum memory technologies.
"By reducing the noise, this breakthrough will allow quantum devices to store information longer and perform calculations with great accuracy," Nichol says.
Because nuclear-spin dark states are very stable, they could be used in quantum computers and other technologies to store information long-term. They could also be used to make incredibly exact measurements by detecting tiny changes in magnetic fields, temperature, or pressure, improving medical imaging and navigation.
The fact that the nuclear-spin dark state was discovered in silicon makes the discovery even more exciting for possible future applications, Nichol says: "Silicon is already widely used in today's technology, which means it may someday be possible to integrate nuclear-spin dark states into future quantum devices."
