Science 3 min read

Two-Qubit Quantum Gate Successfully Built for the First Time

Using “qudits,” Purdue scientists created a quantum gate that works like a transistor, a critical step toward photonic quantum computers.

Image courtesy of Shutterstuck

Image courtesy of Shutterstuck

Where a conventional computer works on bits, quantum computers works on qubits. And where the former have logic gates, the latter has quantum logic gates.

While there’s no real “gate” swinging open and closed, a transistor-based logic gate controls the electric current’s flow through the circuit. On the other hand, a quantum gate controls the flow of quantum information.

A team at Purdue University created a quantum gate that’s like the quantum version of the transistor using qudits. Yes, qudit not qubit, it’s not a typo!

Forget Qubits! Qudit-Based Quantum Gate

If you’re already struggling to grasp the concept of qubits, we’re sorry to throw another similarly sounding term at you: Qudits.

A bit can exist only in either 0 or 1 states at a time. A qubit, however, can exist in both superpositions at the same time.

Then there’s the qudit, which can exist in more states than 0 and 1 at the same time. A qudit can theoretically adopt ten states or more at the same time, and the more states a system can support the more data it can process.

Now, researchers at Purdue’s School of Electrical and Computer Engineering announced they had created the first quantum gate that incorporates qudits for photonic quantum information processing.

The team encoded the qudits, high-dimensional units of information, into photons, making the quantum gate “inherently” more efficient and more stable than qubit gate concepts.

This qudit-based quantum gate also “creates one of the largest entangled states of quantum particles to date – in this case, photons.”

While in previous efforts, other teams could encode 18 qubits in six entangled photons, Purdue researchers were able to pack four qudits, the equivalent of 20 qubits, in only two photons.

The less “real-estate” in quantum computing, the more efficient and cost-effective the system would be. As explained by Poolad Imany, a quantum scientist at Purdue and first author of the study:

“Photons are expensive in the quantum sense because they’re hard to generate and control, so it’s ideal to pack as much information as possible into each photon.”

According to the Purdue team, they created their quantum gate to achieve more entanglement with fewer photons using a set of standard off-the-shelf equipment already in use in the optical telecom industry.

“This gate allows us to manipulate information in a predictable and deterministic way, which means that it could perform the operations necessary for certain quantum information processing tasks,” said Andrew Weiner, Purdue’s Scifres Family Distinguished Professor of Electrical and Computer Engineering.

For their future work, the Purdue team will be testing the qudit-based quantum gate in quantum communications applications, like “high-dimensional quantum teleportation as well as for performing quantum algorithms in applications such as quantum machine learning or simulating molecules.”

Read More: Image of Quantum Entanglement Captured for the First Time

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Zayan Guedim


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