UNSW Engineers Make Massive Quantum Entanglement Breakthrough

A team of quantum engineers at UNSW Sydney has achieved a world-first breakthrough, demonstrating quantum entanglement between two electrons bound to separate phosphorus atoms inside a silicon quantum computer chip. This achievement could be a significant step forward in the quest to build practical quantum computers.

Quantum entanglement, a phenomenon that has perplexed scientists for decades, involves two particles existing in perfect correlation despite having no independent state. Though baffling in theory, entanglement is now considered a crucial resource for developing quantum computers.

Professor Andrea Morello, leader of the UNSW research team, explains the importance of this breakthrough. “Entanglement is the most important resource for building powerful quantum computers,” he says. The team’s research was published in the journal Nature Communications.

Quantum Devices on Silicon Chips

The UNSW team specialises in creating quantum computer devices where information is stored in the magnetic orientation, or ‘spin,’ of individual electrons. These electrons are bound to phosphorus atoms implanted in silicon chips. The approach merges the quantum properties of atoms with the scalability of silicon chips, a material already at the heart of the global semiconductor industry.

“The spin of a phosphorus atom is an excellent quantum bit, or qubit,” says Dr Holly Stemp, lead author of the research paper. “But because atoms are so small, it’s difficult to make them interact with each other, let alone create genuine quantum entanglement.”

Dr Stemp highlights that this is the first time entanglement has been definitively demonstrated between two atoms in silicon. The interaction used to achieve this is based on quantum principles.

“Electrons are not just particles; they behave like waves. When these waves overlap, they create what’s called the ‘exchange interaction,’ which we used to entangle the atoms,” she explains.

The researchers estimated that the atoms were separated by about 20 nanometres—roughly 1/1000th of the thickness of a human hair.

The Challenge of Proving Entanglement

Quantum entanglement is fragile and elusive, making it difficult to demonstrate its existence. To address this challenge, the UNSW team collaborated with experts from Sandia National Laboratories in the US to develop methods for quantifying the fidelity—or degree of perfection—of the quantum operations used to entangle the atoms.

“This isn’t the first time such operations have been attempted,” Dr Stemp says. “But it’s the first time they’ve been done with enough accuracy to prove beyond doubt that we have entanglement between the atoms.”

The team achieved this proof by creating Bell states, named after physicist John Bell, who in 1964 explored the implications of quantum entanglement. Bell’s work challenged long-held notions about the nature of reality and the concept of location.

The breakthrough also required specialised techniques to implant the atoms into silicon chips, a process developed by Professor David Jamieson’s team at the University of Melbourne.

Unlocking Quantum Computing Potential

Entanglement is a critical resource for quantum computing, which could unlock new possibilities in computation. While quantum superposition — the ability of qubits to be in multiple states simultaneously — is often cited as the key to quantum computers’ power, Professor Morello believes entanglement is the real game-changer.

“Entanglement allows us to create digital codewords that do not exist in classical computers,” he explains. “It’s also the quantum link between different qubits, which is essential for scaling up quantum computers.”

The UNSW team’s work could have significant implications for the future of quantum computing. By demonstrating quantum entanglement between two atoms in silicon, they have taken a crucial step toward realising more advanced silicon quantum computer chips.

Dr Stemp echoes this optimism, saying, “Atoms are small and perfect, and it would be amazing if we could handle them using methods borrowed from the trillion-dollar semiconductor industry. Demonstrating quantum entanglement between two atoms unlocks the potential for the next generation of silicon quantum computer chips.”

This achievement signals new possibilities for quantum computing, showing that it may be possible to harness the power of quantum mechanics within silicon, a material that has driven the development of modern computing.

Last Updated on October 2, 2024 by Nick Ross