Efforts to develop quantum computers able to run at higher temperatures is an area of hot pursuit. The most commonly used qubit technology, semiconductor-based superconducting devices typically require a near-absolute zero environment. Recently, Purdue University reported use of a photonic approach to achieve a ‘quantum random walk’ at room temperature.
Their work, reported in ScienceAdvances late last week, uses entangled photons and shows promise as a technique for searching large databases and simulation of many-body physics simulations. In the quantum realm, the laws of random walks are fundamentally different. A quantum agent can move to right and left simultaneously at each step. In other words, a quantum particle can travel in several trajectories at the same time, which can lead to searches of large-scale databases dramatically faster.
“We’re using photons instead of superconducting qubits, which allows our work to be done at room temperature. To be fair, photons have their challenges as well, and cannot yet rival the complexity of operations achieved with superconducting qubits. The point is that quantum walks are a central part of the development of quantum computers. And we’re saying there’s another way of doing quantum walks but at room temperature using photons in a way that hasn’t been done before,” said researcher Andrew Weiner in an article posted on the Purdue website.
Here’s the abstract from their paper:
“Control over the duration of a quantum walk is critical to unlocking its full potential for quantum search and the simulation of many-body physics. Here we report quantum walks of biphoton frequency combs where the duration of the walk, or circuit depth, is tunable over a continuous range without any change to the physical footprint of the system—a feature absent from previous photonic implementations. In our platform, entangled photon pairs hop between discrete frequency modes with the coupling between these modes mediated by electro-optic modulation of the waveguide refractive index. Through control of the phase across different modes, we demonstrate a rich variety of behavior: from walks exhibiting enhanced ballistic transport or strong energy confinement, to subspaces featuring scattering centers or local traps. We also explore the role of entanglement dimensionality in the creation of energy bound states, which illustrates the potential for these walks to quantify high-dimensional entanglement.”
Currently there are multiple qubit technologies vying for sway in quantum computing.
Header image caption and credit: This image shows how two quantum-entangled photons would move across colors or light frequencies. (Purdue University image/Allison Rice)
Link to article: https://www.purdue.edu/newsroom/releases/2020/Q3/quantum-rainbow-photons-of-switching-colors-allow-room-temperature-quantum-computing.html
Link to ScienceAdvances paper: https://advances.sciencemag.org/content/6/29/eaba8066?_ga=2.108520194.1086147472.1595429396-952259532.1595429396