Physicists from RIKEN have successfully linked two silicon spin qubits that are physically separated from one another through a technique known as coherent spin shuttling, marking significant progress towards the realization of large-scale quantum computing. This achievement addresses a key difficulty in quantum computing – connecting quantum dots located at a considerable distance from each other, an essential requirement for escalating quantum computers from a capacity of hundreds to millions of qubits.
This achievement in linking two remote qubits contributes to the development of bigger, more intricate quantum computers utilizing silicon quantum dots.
RIKEN’s scientists have managed to connect two spatially separated qubits – the basic units of quantum information, paving the way for the expansion of silicon-based quantum computers.
Major IT companies such as IBM, Google, and Microsoft are competing in the development of quantum computers, with some having already shown the potential to significantly surpass traditional computers in performing certain calculations. However, scaling up these quantum computers from a couple of hundred qubits to millions remains a critical challenge for commercial applicability.
Silicon quantum dots, tens of nanometers in diameter, are among the leading technologies for achieving large-scale quantum computing. They offer the benefit of being producible with existing silicon manufacturing technology. The difficulty lies in the fact that while connecting adjacent quantum dots is simple, linking those located far from one another has been challenging.
Figure 1: RIKEN researchers successfully linked two distant qubits (depicted as red and blue spheres with black arrows gray cones on the left and right) using coherent shuttling of one of the qubits (blue spheres). Credit: © 2023 RIKEN Center for Emergent Matter Science
“To connect a large number of qubits, we need to densely pack them into a minimal area,” explains Akito Noiri from the RIKEN Center for Emergent Matter Science, adding that it’s incredibly challenging to wire connect such densely packed qubits.
Noiri, along with his team, have now accomplished a two-qubit logic gate between physically separated silicon spin qubits (Fig. 1).
“This is the first time a reliable logic gate has been formed by two distant qubits, despite many attempts using various strategies. This demonstration propels the potential of scaling up quantum computing based on silicon quantum dots,” Noiri states.
Akito Noiri (far right) and his team have exhibited a logic gate with two distant qubits connected via coherent spin shuttling. Credit: © 2023 RIKEN
The researchers employed coherent spin shuttling to link the two qubits, a technique that facilitates the movement of single spin qubits across a series of quantum dots without disturbing their phase coherence, a critical characteristic for quantum computers as it carries information. The method involves applying a voltage to move electrons through an array of qubits.
Even though the actual distance between the two qubits was relatively small, Noiri is optimistic that it can be expanded in upcoming studies. “We aim to increase the distance to about a micrometer, making the method more feasible for future applications,” he adds.
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
Table of Contents
Frequently Asked Questions (FAQs) about Scaling Quantum Computing
What have RIKEN researchers accomplished in the field of quantum computing?
RIKEN researchers have successfully linked two physically distant silicon spin qubits using a technique known as coherent spin shuttling. This marks significant progress in the field of quantum computing, particularly in overcoming the challenge of connecting quantum dots that are far from each other, a crucial step in scaling quantum computers from hundreds to millions of qubits.
What technology is being used in this development?
The technology used in this development is silicon quantum dots. These are among the leading technologies for achieving large-scale quantum computing. A key advantage of silicon quantum dots is that they can be fabricated using existing silicon manufacturing technology.
What is coherent spin shuttling?
Coherent spin shuttling is a method that allows single spin qubits to be moved across an array of quantum dots without affecting their phase coherence. Phase coherence is a crucial property for quantum computers as it carries information. This technique involves pushing electrons through an array of qubits by applying a voltage.
How will this breakthrough help in the development of quantum computers?
The successful linking of two distant qubits paves the way for the development of larger, more intricate quantum computers based on silicon quantum dots. It addresses a key challenge of linking quantum dots located at a significant distance from each other, an essential requirement for escalating quantum computers from hundreds to millions of qubits.
What are the commercial implications of this breakthrough?
Major IT companies, including IBM, Google, and Microsoft, are actively working on the development of quantum computers. The ability to link distant qubits, a task accomplished by the RIKEN team, is a major stride towards the goal of creating commercially viable quantum computers capable of outperforming traditional computers in performing certain calculations.
More about Scaling Quantum Computing
- RIKEN Center for Emergent Matter Science
- Introduction to Quantum Computing
- Quantum Computing and Information
- Quantum Computing at Google
- Silicon Quantum Dots
- Quantum Dots and Their Applications
- Quantum Computing: Coherent Spin Shuttling
- Akito Noiri Research
- Nature Communications Journal
