RIKEN researchers have related two bodily distant silicon spin qubits utilizing a technique known as coherent spin shuttling, a significant step towards large-scale quantum computing. This breakthrough overcomes the problem of linking far-apart quantum dots, a essential hurdle in scaling quantum computer systems from a whole lot to hundreds of thousands of qubits.
The linking of two distant qubits will assist to develop bigger, extra advanced quantum computer systems based mostly on silicon quantum dots.
In an indication that guarantees to assist scale up quantum computer systems based mostly on tiny dots of silicon, RIKEN physicists have succeeded in connecting two qubits—the fundamental unit for quantum data—which are bodily distant from one another.
Many large IT gamers—together with the likes of IBM, Google, and Microsoft—are racing to develop quantum computer systems, a few of which have already demonstrated the power to drastically outperform standard computer systems for sure varieties of calculations. However one of many biggest challenges to growing commercially viable quantum computer systems is the power to scale them up from 100 or so qubits to hundreds of thousands of qubits.
By way of applied sciences, one of many front-runners to realize large-scale quantum computing is silicon quantum dots that are a few tens of nanometers in diameter. A key advantage is that they can be fabricated using existing silicon fabrication technology. But one hurdle is that, while it is straightforward to connect two quantum dots that are next to each other, it has proved difficult to link quantum dots that are far from each other.
Figure 1: RIKEN researchers have linked two distant qubits (red and blue spheres with black arrows gray cones on left and right) by coherent shuttling of one of the qubits (blue spheres). Credit: © 2023 RIKEN Center for Emergent Matter Science
“In order to connect many qubits, we have to densely cram many of them into a very small area,” says Akito Noiri of the RIKEN Center for Emergent Matter Science. “And it’s very hard to use wires to connect such very densely packed qubits.”
Now, Noiri and co-workers have realized a two-qubit logic gate between physically distant silicon spin qubits (Fig. 1).
“While there has been a lot of work in this area using various approaches, this is the first time that anyone has succeeded in demonstrating a reliable logic gate formed by two distant qubits,” says Noiri. “The demonstration opens up the possibility of scaling up quantum computing based on silicon quantum dots.”
Akito Noiri (far right) and co-workers have demonstrated a logic gate based on two distant qubits linked by coherent spin shuttling. Credit: © 2023 RIKEN
To connect the two qubits, the team used a method known as coherent spin shuttling, which allows single spin qubits to be moved across an array of quantum dots without affecting their phase coherence—an important property for quantum computers since it carries information. This method involves pushing electrons through an array of qubits by applying a voltage.
Although the physical separation between the two qubits was relatively short, Noiri is confident that it can be extended in future studies. “We want to increase the separation to about a micrometer or so,” he says. “That will make the method more practical for future use.”
Reference: “A shuttling-based two-qubit logic gate for linking distant silicon quantum processors” by Akito Noiri, Kenta Takeda, Takashi Nakajima, Takashi Kobayashi, Amir Sammak, Giordano Scappucci and Seigo Tarucha, 30 September 2022, Nature Communications.
DOI: 10.1038/s41467-022-33453-z