Introduction

In an astonishing leap forward in the realm of quantum computing, Quantinuum has successfully demonstrated a record-breaking Greenberger-Horne-Zeilinger (GHZ) state utilizing 50 entangled logical qubits. To contextualize this remarkable achievement, let’s first delve into what a GHZ state actually is and why it warrants such excitement in the scientific community.

Understanding GHZ States

Most people are familiar with the concept of two entangled qubits, known as a Bell pair. These qubits are intrinsically linked, whereby a change in the state of one results in a corresponding change in the other, regardless of the physical distance separating them. Albert Einstein famously dubbed this perplexing phenomenon “spooky action at a distance.” A GHZ state extends this idea, entangling more than two qubits, such that when one qubit is measured, all qubits in the state change synchronously.

Characteristics of Ideal GHZ States

In an ideal GHZ state, all qubits exist in a superposition of "0" and "1" states until they are observed, resulting in a uniform collapse to either the "000...0" state or "111...1" state upon measurement. The recent experimental results from Quantinuum showcased some errors, which were depicted in a chart with error bars. The goal is for 50% of the measurements to illustrate a complete collapse to "000...0" and the other 50% to "111...1", but imperfections exist in the current setup.

Technological Achievements by Quantinuum

Quantinuum utilized its advanced 56-qubit H2-1 processor to achieve this GHZ state, employing a sophisticated [[52,50,2]] error detection code that required 52 physical qubits to generate 50 logical qubits with a code distance of 2. It is pivotal to note that while this code effectively detects errors, it does not correct them instantaneously. Instead, once an error is identified, the quantum processor can repeat the operation until a fault-free outcome is obtained. The results were clearly shown in a comparative analysis, where the orange bars indicated outcomes without using the error detection code while blue bars showcased improved results when the code was active.

Comparison with Other Achievements

The groundbreaking findings from Quantinuum more than double the previous record set by Microsoft and Atom Computing, who demonstrated entanglement with 24 logical qubits on a neutral atom-based processor, making use of a [[4,2,2]] error detection and loss code. Their system required approximately 48 physical qubits to create those 24 logical qubits.

Future Implications

In a fiercely competitive quantum computing landscape, numerous vendors are striving to outperform each other by establishing new benchmarks for various performance metrics. Quantinuum's latest feat stands as a significant milestone for GHZ states in 2024. However, industry experts anticipate that as technology evolves, larger and more sophisticated processors, along with enhanced error detection and correction codes, will emerge, enabling even greater achievements.

Conclusion

This groundbreaking accomplishment not only amplifies the contention within the quantum computing sector but also raises the question: What next? What heights can we expect quantum processors to reach in the near future? For those eager to learn more about the technological advancements by Quantinuum, a detailed presentation by David Hayes, Director of Computational Theory and Design, is available from the recent Q2B Silicon Valley conference and can be accessed online. Stay tuned, as the race for quantum supremacy rages on!