New Superconducting Material Could Make Disruption Resistant Quantum Computers

In the new study, Yufan Li and colleagues found that a ring of β-Bi2Pd already naturally exists between two states in the absence of an external magnetic field. Current can inherently circulate both clockwise and counterclockwise, simultaneously, through a ring of β-Bi2Pd.

Above – A visual representation of a qubit, which can exist simultaneously between two states. A famous example of a qubit is Schrodinger’s cat, a hypothetical cat that can be both dead and alive. Similarly, a flux qubit, or a ring made of a superconducting material, can have electric current flowing both clockwise and counterclockwise at the same time.
Credit: Yufan Li

Quantum computers with the ability to perform complex calculations, encrypt data more securely and more quickly predict the spread of viruses, may be within closer reach thanks to a new discovery by Johns Hopkins researchers.

A ring of β-Bi2Pd already exists in the ideal state and doesn’t require any additional modifications to work. This could be a game changer. The next step is to look for Majorana fermions within β-Bi2Pd; Majorana fermions are particles that are also anti-particles of themselves and are needed for the next level of disruption-resistant quantum computers: topological quantum computers.

Majorana fermions depend on a special type of superconducting material—a so-called spin-triplet superconductor with two electrons in each pair aligning their spins in a parallel fashion—that has thus far been elusive to scientists. Now, through a series of experiments, Li and colleagues found that thin films of β-Bi2Pd have the special properties necessary for the future of quantum computing.

Scientists have yet to discover the intrinsic spin-triplet superconductor needed to advance quantum computing forward, but Li is hopeful that the discovery of β-Bi2Pd’s special properties, will lead to finding Majorana fermions in the material next.

“Ultimately, the goal is to find and then manipulate Majorana fermions, which is key to achieving fault-tolerant quantum computing for truly unleashing the power of quantum mechanics,” says Li.

Science – Observation of half-quantum flux in the unconventional superconductor β-Bi2Pd

Unconventional oscillations
At sufficiently low temperatures, superconductors expel an applied magnetic field. However, if the topology of the superconductor is nontrivial—for example, if there is a hole in the sample—there can be a nonzero magnetic flux inside the hole. This flux can only take certain discrete values, and the superconducting critical temperature has maxima at the corresponding values of the magnetic field. Li et al. studied these so-called Little-Parks oscillations in superconducting rings made out of polycrystalline thin films of β-Bi2Pd. They found that the phase of the oscillations was shifted by π compared with oscillations observed in most superconductors, as predicted for certain unconventional pairing symmetries.

Abstract
Magnetic flux quantization is one of the defining properties of a superconductor. We report the observation of half-integer magnetic flux quantization in mesoscopic rings of superconducting β-Bi2Pd thin films. The half-quantum fluxoid manifests itself as a π phase shift in the quantum oscillation of the superconducting critical temperature. This result verifies unconventional superconductivity of β-Bi2Pd and is consistent with a spin-triplet pairing symmetry. Our findings may have implications for flux quantum bits in the context of quantum computing.

SOURCES- John Hopkins, Science
Written By Brian Wang, Nextbigfuture.com

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