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Category: quantum physics

How true Eric Klien?

Something to look forward to: Solid-state batteries are still nebulous outside of the lab. Still, automakers are scrambling to be the first in the race to build the first electric car to take advantage of the added energy density and better safety when compared to lithium-ion designs. To that end, they’re investing in companies like QuantumScape, Solid Power, and Sakuu to develop manufacturing techniques that either build on existing approaches or rely on new additive manufacturing technology.

Earlier this year, an MIT study revealed that lithium-ion battery costs have fallen by more than 97 percent since its commercial introduction almost 30 years ago. Not only that, but industry watchers are optimistic that by2025lithium-ion battery manufacturing capacity will have tripled while the price per kilowatt-hour is expected to dip below $100.

The dip has spurred automakers to get serious about making electric cars, but the fact of the matter is that price is only part of the equation of making it a better choice for consumers and the environment. The importance of safety cannot be overstated, as evidenced by GM’s recall last year for more than 68,000 Chevy Bolts. On that front, researchers are hard at work developing a new cathode coating that not only makes lithium-ion batteries safer but could also improve their energy density.

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Partition functions are ubiquitous in physics: They are important in determining the thermodynamic properties of many-body systems and in understanding their phase transitions. As shown by Lee and Yang, analytically continuing the partition function to the complex plane allows us to obtain its zeros and thus the entire function. Moreover, the scaling and nature of these zeros can elucidate phase transitions. Here, we show how to find partition function zeros on noisy intermediate-scale trapped-ion quantum computers in a scalable manner, using the XXZ spin chain model as a prototype, and observe their transition from XY-like behavior to Ising-like behavior as a function of the anisotropy. While quantum computers cannot yet scale to the thermodynamic limit, our work provides a pathway to do so as hardware improves, allowing the future calculation of critical phenomena for systems beyond classical computing limits.

Interacting quantum systems exhibit complex phenomena including phase transitions to various ordered phases. The universal nature of critical phenomena reduces their description to determining only the transition temperature and the critical exponents. However, numerically calculating these quantities for systems in new universality classes is complicated because of critical slowing down, requiring increasing resources near the critical point. An alternative approach is to analytically continue the calculation of the partition function to the complex plane and determine its zeros.

The partition function is a positive function of multiple real parameters representing physical quantities such as temperature and applied fields. When the partition function is analytically continued in one of the respective parameters, its zeros show notable structure for a variety of models of interest. Lee and Yang (1, 2) studied the partition function zeros of Ising-like systems in the complex plane of the magnetic field h and found that, at the critical temperature (and in the thermodynamic limit), the loci of zeros pinch to the real axis. Alternatively, Fisher (3) studied the partition function zeros by making the inverse temperature β complex.

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A new project will use the electric field in an accelerator cavity to try to levitate a tiny metallic particle, allowing it to store quantum information.

Quantum computing could solve problems that are difficult for traditional computer systems. It may seem like magic. One step toward achieving quantum computing even resembles a magician’s trick: levitation. A new project at the U.S. Department of Energy’s Thomas Jefferson National Accelerator Facility will attempt this trick by levitating a microscopic particle in a superconducting radiofrequency (SRF) cavity to observe quantum phenomena.

Typically at Jefferson Lab and other particle accelerator facilities, SRF cavities enable studies of the atom.

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Quantum matter can be solid and fluid at the same time—a situation known as supersolidity. Researchers led by Francesca Ferlaino have now created for the first time this fascinating property along two dimensions. They now report in the journal Nature on the realization of supersolidity along two axes of an ultracold quantum gas. The experiment offers many possibilities for further investigation of this exotic state of matter.

Quantum gases are very well suited for investigating the microscopic consequences of interactions in matter. Today, scientists can precisely control individual particles in extremely cooled gas clouds in the laboratory, revealing phenomena that cannot be observed in the every-day world. For example, the in a Bose-Einstein condensate are completely delocalized. This means that the same atom exists at each point within the condensate at any given time. Two years ago, the research group led by Francesca Ferlaino from the Department of Experimental Physics at the University of Innsbruck and the Institute of Quantum Optics and Quantum Information at the Austrian Academy of Sciences in Innsbruck managed for the first time to generate supersolid states in ultracold quantum gases of magnetic atoms. The magnetic interaction causes the atoms to self-organize into droplets and arrange themselves in a regular pattern.

“Normally, you would think that each atom would be found in a specific droplet, with no way to get between them,” says Matthew Norcia of Francesca Ferlaino’s team. “However, in the supersolid state, each particle is delocalized across all the droplets, existing simultaneously in each droplet. So basically, you have a system with a series of high-density regions (the droplets) that all share the same delocalized atoms.” This bizarre formation enables effects such as frictionless flow despite the presence of spatial order (superfluidity).

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