TECH

A two-qudit gate, among the first of its kind, maximizes the entanglement of photons so that quantum information can be manipulated more predictably and reliably. Image credit: Purdue University/Allison Rice
Researchers Build Transistor-Like Gates With Highly-Efficient Quantum 'Qudits'

Purdue University researchers were able to build a gate (a quantum-version of a transistor) using two qudits, which represent the most stable form of qubits.
Qubits are notorious for being highly unstable, and the vast majority of quantum researches have gone to finding ways to make qubits more stable. It is also why there are so many types of universal quantum computers, from superconducting and trapped-ion quantum computers to the most exotic topological quantum computers.
The Purdue researchers created a more stable version of qubits by embedding them into photons (particles of light not easily disturbed by environmental noise). This new version is called quit, and unlike qubits that can exist only in the superposition of 0 and one states, qudits can exist in superpositions of 0, 1, and 2 states. More states mean that more data can be encoded and processed by a smaller amount of qubits, making the new solution much more efficient.
Previous photonic approaches were able to encode 18 qubits within six entangled photons. Through the entanglement process, you can interconnect two particles so that when you change the state of one the other changes as well.
The Purdue researchers were able to use a gate to encode 20 qubits in only two photos. Poolad Imany, a postdoctoral researcher at Purdue's School of Electrical and Computer Engineering, explained why it's preferable to use as few photos as possible to encode information:
"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."
Typically, gates built on photonic platforms do not work as well because photons do not naturally interact with each other well, which makes it difficult to manipulate the state of one photon to affect another.
The Purdue researchers were able to encode the quantum information in the time and frequency domains of the four photons. This made operating the quantum gates deterministic as opposed to probabilistic, which means the operations could be performed as necessary. This generated four fully-entangled qudits, which occupy a Hilbert space of 1,048,576 dimensions, or possibilities.
The Purdue team intends to use its latest research to build algorithms for quantum machine learning applications and for simulating molecules. by Lucian Armasu