Sydney, Australia: Today, team Diraq has achieved an important milestone – demonstrating violation of Bell’s inequality in gate-defined quantum dots – a key performance benchmark for qubit fidelity and quantum entanglement. 

This achievement underscores the importance of innovation in high-fidelity control and qubit entanglement to overcome the fundamental challenges of quantum operation. 

With results published in Nature Communications, the findings are a crucial validation of performance for scalable, fault-tolerant quantum computers based on Diraq’s silicon spin qubit technology. 

Diraq Founder and CEO, Andrew Dzurak, said, “Entanglement is arguably the most profound property of quantum mechanics and the fundamental basis for quantum computers to work and gain quantum advantage. Using contemporary tools for manipulating electron spin qubits in silicon quantum dots and improving their performance, our team at Diraq has now convincingly shown a violation of Bell’s inequality, demonstrating the genuine quantum nature of the entangled states.” 

The results are very promising for Diraq’s technology based on electron spin qubits in silicon. 

Dzurak continues, “We believe this is a world-first demonstration of violating Bell’s inequality with electron spin qubits in quantum dots, which is very satisfying. Furthermore, these results will directly help in our device design, informing our approach to shape and refine the structure of our Diraq quantum dot qubits, paving the way for scalable, fault-tolerant quantum computers based on silicon spin qubits”. 

The lead author Paul Steinacker and contributing authors detailed their findings in the paper “Bell inequality violation in gate-defined quantum dots”.

Key performance benchmarks were achieved by using heralded initialization and calibration via gate set tomography, with highlights including: 

•  Violation of Bell’s inequality with a very high Bell signal of S=2.731;
• A Bell state fidelity above 97%, without correcting for readout errors;
• Violation of the classical limit even at elevated temperatures of 1.1K. 

Steinacker commented “The results provide a meaningful indication of the high performance and maturity of the SiMOS platform, as the inequality can only be violated by achieving high fidelities in state preparation, manipulation and measurement simultaneously”.  

Ultimately, full-scale fault-tolerant quantum computing processors require quantum logic operations across the entire chip with errors below the quantum error correction threshold to harness their full capabilities. 

The findings of this research contribute to unlocking the mystery of quantum entanglement and pave the way for scalable, fault-tolerant quantum computers based on silicon spin qubits.

Read Nature's article here.