Tag: Materials Science

Half-Quantum Step Toward Quantum Advantage🤔

Credit: Yufan Li, Johns Hopkins University

A famous metaphor for a qubit is Schrodinger’s hypothetical cat that can be both dead and alive. A flux qubit, a ring made of superconducting material, can have electric current flowing clockwise and counterclockwise simultaneously with an external field.

The Science

Superconductors are materials that have no electrical resistance below a critical temperature. They typically push away magnetic fields, as if they are surrounded by an anti-field shield. But to use superconductors as qubits (the unit of a quantum computer), scientists had to surround them with magnetic fields. Researchers recently measured a surprising effect for a new type of superconductor: bismuth palladium (β-Bi2Pd). Even when there was no magnetic field around this superconductor, they found it existed between two states. That’s a necessary requirement for creating a qubit. This superconductor may host a Majorana fermion, an exotic quasiparticle. Scientists have proposed the idea of Majorana fermions, but have not observed them in experiments. 

The Impact

Classical computers process information using binary states (0 and 1), called bits. Quantum computers use quantum bits (qubits). However, a qubit can be both 0 and 1 at the same time. Qubits enable quantum computers to perform certain calculations at speeds many times faster than a classical computers. However, large-scale quantum computers need qubits that are much more stable than those currently available. Scientists are researching many different possible approaches to qubits, including photons, trapped ions, loops of superconducting material, and Majorana fermions. Majorana fermions are a promising candidate for stable qubits.  


Scientists are currently looking for material systems that can support long-lived, coherent quantum phenomena that can be used for the development of qubits for future quantum computers.  One actively investigated system is based on Majorana fermions. In condensed matter physics, Majorana fermions are quasiparticles that are their own antiparticles, a fascinating quantum property. Because they always come in pairs, entangled Majorana quasiparticles could store quantum information at two discrete locations. For example, it could store data at opposite ends of one-dimensional wires. Scientists have suggested that Majorana fermions might exist in a spin-triplet superconductor (a superconductor in which pairs of electrons align their spins in parallel, resulting in a net total spin). In this research, scientists observed a half-quantum flux or half-quantum step when measuring the influence of a magnetic field on patterned rings of thin films of β-Bi2Pd. This observation proves unconventional Cooper pairing of electrons. The half-quantum flux was first observed in high-temperature copper-oxide superconductors. Other experiments reported in the literature are also consistent with spin-triplet pairing in this material. Spin-triplet superconductors have the necessary but not sufficient potential to host topologically-protected Majorana fermions. These quasiparticles could serve as a platform for the development of stable qubits for quantum computers with long coherence times and robustness toward atomic perturbations. What makes the half-quantum flux superconducting ring especially attractive is that such a field-free qubit device may enable practical applications of flux qubits for quantum computing.


This work was supported by the U.S. Department of Energy (DOE), Basic Energy Sciences, including the SHINES Energy Frontier Research Center. E-beam lithography was conducted at the University of Delaware Nanofabrication Facility (UDNF) and the NanoFab laboratory of NIST (CNST).

Saving the Planet, One Drop at a Time

Scientists at the Johns Hopkins Applied Physics Laboratory (APL), in Laurel, Maryland, have identified highly absorbent materials that can extract drinkable water out of thin air — which could potentially lead to technologies that supply potable water in the driest areas on the planet.

For many of the world’s poor, one of the greatest environmental threats to health remains lack of access to safe water. Scientists at the Johns Hopkins University Applied Physics Laboratory (APL), in Laurel, Maryland, have identified highly absorbent materials that can extract drinkable water out of thin air – which could potentially lead to technologies that supply potable water in the driest areas on the planet.

The researchers – a team from APL’s Research and Exploratory Development Department led by Zhiyong Xia, Matthew Logan and Spencer Langevin – describe their discovery in the Jan. 30 issue of Scientific Reports, a journal of the Nature Research family. 

Their research leverages metal-organic frameworks (MOFs), an amazing next-generation material that has the largest known surface areas per gram – a single gram of the MOF can soak up a football field’s worth of material, if the material were laid in a single layer across the field. The sponge-like crystals can be used to capture, store and release chemical compounds – like water – and the large surface area offers more space for chemical reactions and adsorption of molecules.

MOFs have shown promise for water harvesting, but little research has been done to determine the best properties for fast and efficient production of water.

“Initial experiments have proved that the concept can work,” says Xia. “But the problem has been capacity. Other research teams have been able to produce as much as about  1.3 liters of water per day per kilogram of sorbent  under arid conditions – enough only for one person. To create an optimal water harvesting device requires a better understanding of the structure property relationship controlling absorption and delivery.”

Xia and his team studied a series of MOFs – unraveling the fundamental material properties that govern the kinetics of water sequestration in this class of materials as well as investigating how much water they can absorb. They also explored the potential impact of temperature, humidity and powder bed thickness on the adsorption-desorption process to see which one achieved optimal operational parameters.

“We identified a MOF that could produce 8.66 liters of water per day per kilogram of MOF under ideal conditions, an extraordinary finding.” Xia said. “This will help us deepen our understanding of these materials and guide the discovery of next-generation water harvesting methods.”

Xia and his team are now exploring other MOFs with low relative humidity influx points, high surface areas, and polar functional properties to see how they perform in very dry environments. They are also exploring different configurations of MOFs to determine which allow for optimal absorption.

The researchers drew on APL’s ongoing efforts in water purification methods. APL has developed a novel way to remove highly toxic perfluoroalkyl substances — an ever-expanding group of manufactured chemicals that are widely used to make various types of everyday products — from drinking water. A separate effort yielded a cost-effective method to remove toxic heavy metal ions from drinking water.

“Our scientists’ and engineers’ collective strengths and expertise in materials and chemistry have positioned APL to make extraordinary impact and invent the future of clean drinking water for deployed warfighters, as well as for citizens around the world,” said Ally Bissing-Gibson, APL’s Biological and Chemical Sciences program manager. “We look forward to saving the planet, one drop at a time.”