Synthetic Magnetism Leads Photons on a 2D Quantum Walk
Randomness governs many things, from the growth of cell colonies and the agglomeration of polymers to the shapes of tendrils that form when you pour cream into a cup of coffee.Since as early as 1905, scientists have described these seemingly unrelated phenomena in a unified way: as random walks. By imagining that individual particles or molecules are constantly taking steps in a random direction, researchers have successfully modeled many of the complexities of classical physics.More recently, scientists 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. 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.
Remote Quantum Systems Produce Interfering Photons
Scientists at the Joint Quantum Institute (JQI) have observed, for the first time, interference between particles of light created using a trapped ion and a collection of neutral atoms. Their results could be an essential step toward the realization of a distributed network of quantum computers capable of processing information in novel ways.
Quantum Simulation of Hyperbolic Space with Circuit Quantum Electrodynamics: From Graphs to Geometry
Hybrid Device among First to Meld Quantum and Conventional Computing
Researchers at the University of Maryland (UMD) have trained a small hybrid quantum computer to reproduce the features in a particular set of images. The result, which was published Oct. 18, 2019 in the journal Science Advances, is among the first demonstrations of quantum hardware teaming up with conventional computing power—in this case to do generative modeling, a machine learning task in which a computer learns to mimic the structure of a given dataset and generate examples that capture the essential character of the data.
Stretched Photons Recover Lost Interference
The smallest pieces of nature—individual particles like electrons, for instance—are pretty much interchangeable. An electron is an electron is an electron, regardless of whether it’s stuck in a lab on Earth, bound to an atom in some chalky moon dust or shot out of an extragalactic black hole in a superheated jet. In practice, though, differences in energy, motion or location can make it easy to tell two electrons apart.One way to test for the similarity of particles like electrons is to bring them together at the same time and place and look for interference—a quantum effect that arises when particles (which can also behave like waves) meet. This interference is important for everything from fundamental tests of quantum physics to the speedy calculations of quantum computers, but creating it requires exquisite control over particles that are indistinguishable.With an eye toward easing these requirements, researchers at the Joint Quantum Institute (JQI) and the Joint Center for Quantum Information and Computer Science (QuICS) have stretched out multiple photons—the quantum particles of light—and turned three distinct pulses into overlapping quantum waves. The work, which was published recently in the journal Physical Review Letters, restores the interference between photons and may eventually enable a demonstration of a particular kind of quantum supremacy—a clear speed advantage for computers that run on the rules of quantum physics.
Ions clear another hurdle toward scaled-up quantum computing
Scientists at the Joint Quantum Institute (JQI) have been steadily improving the performance of ion trap systems, a leading platform for future quantum computers. Now, a team of researchers led by JQI Fellows Norbert Linke and Christopher Monroe has performed a key experiment on five ion-based quantum bits, or qubits. They used laser pulses to simultaneously create quantum connections between different pairs of qubits—the first time these kinds of parallel operations have been executed in an ion trap. The new study, which is a critical step toward large-scale quantum computation, was published on July 24 in the journal Nature.