Advances in Photonics-Based Quantum Walks Studies Permitting Ever-Increasing Complexity of Quantum Simulations

Synthetic magnetism leads photons on a 2-D quantum walk

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+  …[S]cientists have brought the idea of a random walk to the quantum world, where the “walkers” can exhibit nonclassical behaviors like quantum superposition and entanglement. These quantum random walks can simulate quantum systems and may eventually be used to implement speedy quantum computing algorithms. However, this will require the walker to move in multiple dimensions (2D and higher), which has been difficult to achieve in a manner that is both practical and scalable.

+  Quantum walks that use photons—the quantum particles of light—are particularly promising, since photons can travel long distances as energy in wave form. However, photons don’t carry an electric charge, which makes it difficult to fully control their motion. In particular, photons won’t respond to magnetic fields—an important tool for manipulating other particles like atoms or electrons.

“This work is an important step toward more practical photonic-based quantum random walks,” says Waks. “Exploring how these systems behave and how we can control them will allow us to perform more complex quantum simulations.”

+  To address these shortcomings, researchers at the Joint Quantum Institute (JQI) have adopted a scalable method for orchestrating 2D quantum random walks of photons—results that were recently published in the journal Physical Review Letters. The research team, led by JQI Fellows Edo Waks and Mohammad Hafezi, developed synthetic magnetic fields in this platform that interact with photons and affect the movement of photonic quantum walkers.

+  In their demonstration of a 2D quantum random walk, the researchers created a synthetic magnetic field for the photons—something that may one day allow for more complex quantum walks or even simulations of arbitrary quantum systems. By modifying the wave nature of the photon pulses based on the direction they moved at each step, the team created an effective magnetic field on the walkers. The researchers then measured how far the walkers traveled from their initial locations and observed that they did not go as far as they did without the field—a suppression predicted by theory.

Source:  Joint Quantum Institute.  Alexandra Brozena,  Synthetic magnetism leads photons on a 2-D quantum walk…

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