A research team, headed by Professor Dominik Zumbühl at the University of Basel, has achieved a breakthrough that could make quantum computing a reality. They were able to tune a spin qubit, increasing both its operating speed and coherence time simultaneously. This breakthrough might lead to more powerful quantum processors, in the long run helping realize the benefits of quantum computing. The findings, published in the journal Nature Communications, reveal a novel method that employs a unique nanowire structure to optimize qubit performance.
This study is centered on a singular spin qubit represented by a charge carrier spin. It includes a core nanowire, just 20 nanometers in diameter, of germanium that is sheathed with a thin layer of silicon. To do this, the team uses a special type of spin-orbit coupling. This allows them to precisely control the energy states inside the nanowire. Miguel J. Carballido, the first author of the study, described their approach as groundbreaking.
Innovative Techniques for Quantum Control
Lasers, though, allow you to sweep through the frequencies faster than natural transitions between qubit states. This leads to a reduced coherence time. Zumbühl’s lab has demonstrated a promising technique that works at a relatively high temperature of 1.5 kelvin. This is in sharp contrast to the less than 100 millikelvin often required by most qubit technologies.
In this new application, researchers are able to reproducibly control the energy levels of holes inside the nanowire. They do this by using an electric voltage. Such manipulation gives us unprecedented ability to hone in on the qubit’s performance. Carballido pointed out that, “In this way, we were able to increase the coherence time of our qubit fourfold while making the drive three times faster.”
Compared to an air bubble, their device has more surprising benefits such as higher stability and control of quantum states. This similarity highlights the creative quality of their method and sheds light on the inner workings of their results.
Future Applications in Quantum Computing
For Zumbühl’s research team, the objective is straightforward. They’d like to bring their approach further than this proof-of-concept and expand it to two-dimensional semiconductors and multi-qubit systems. Quantum computing’s implications are so great as to be almost incalculable. This breakthrough promises to lead to faster, stronger, more reliable quantum processors of the future.
Daniel Loss, a professor at the University of Basel, headed up this group of theoretical physicists. Specifically, they worked hand-in-hand to predict mechanisms through which faster drive and longer coherence time could be achieved. These experimentalists’ efforts wouldn’t have been possible without a strong theoretical collaboration. This collaborative spirit has been key to the unique research.
The “plateau trick,” as it has been called, works now only in the nanowires made in Basel. In such lattices, holes are restricted from propagating in more than one spatial dimension. This limitation has been key for realizing the results reported in … This limitation is intentional and underscores the one-of-a-kind, yet potentially highly specific, nature of Zumbühl’s approach to quantum technology.
Implications for Quantum Research
The potential applications of this scientific breakthrough reach well past the lab. Through maximizing speed and coherence time simultaneously in the context of spin qubits, researchers are introducing vastly superior modes of computation that can be achieved through quantum systems. These types of innovations might propel near-term, real-world uses in areas like cryptography, materials science and modeling complex systems.
Miguel J. Carballido reflected on the team’s innovative mindset during their research process: “Initially, we asked ourselves what would happen if we simply ‘stepped on the accelerator’ of our qubit—however, not just in any way, but the smart way.” This relentless pursuit of the betterment of qubit performance fueled all of their research and efforts, but reflects the vision quest mindset that defines today’s cutting-edge quantum research.