A recent study has revealed significant behavior regarding how electric current flows through quantum superconductors, which could lead to advancements in technologies such as quantum computing.
A recent study has revealed significant behavior regarding the flow of electric current through superconductors, which could enhance future technologies for controlled quantum information processing.
This research was co-authored by Babak Seradjeh, a Professor of Physics from the College of Arts and Sciences at Indiana University Bloomington, alongside theoretical physicists Rekha Kumari and Arijit Kundu from the Indian Institute of Technology Kanpur. Although the study is theoretical, the research team validated their findings using numerical simulations. The study, published in Physical Review Letters, the leading journal in the field of physics, concentrates on “Floquet Majorana fermions” and their influence on a phenomenon referred to as the Josephson effect. This exploration could enable more precise control of the dynamics in driven quantum systems.
Potential advances in quantum computing
Building a full-scale quantum computer is complicated by one major issue: instability. This instability arises primarily from “quantum decoherence,” a process where qubits, or quantum bits, lose their sensitive quantum state due to environmental interference, including temperature changes or electromagnetic noise.
Qubits can be created using various physical systems, including trapped ions, optical arrays, or superconductors—materials that can conduct electricity without energy loss when cooled to near absolute zero. However, keeping quantum computers sufficiently cold to maintain stability is energy-intensive; if qubits warm up, they become increasingly unstable, leading to a rise in errors.
One potential solution to this problem is searching for “room-temperature superconductors,” often seen as the ultimate goal in superconductivity. Achieving superconductivity near room temperature (around 20-25 degrees Celsius or 68-77 degrees Fahrenheit) could revolutionize technology, enabling lossless power transmission and greatly enhancing electronic efficiency and cryptographic security.
Professor Seradjeh and his team approach the challenge of decoherence by encoding quantum information in a non-local manner, distributing it over a larger spatial area, thus making it less susceptible to local noise and disturbances.
Why are “Floquet Majorana Fermions” significant for quantum computing?
Named after Italian physicist Ettore Majorana, Majorana fermions are subatomic particles that exhibit unusual behavior; unlike most particles, they are their own antiparticles. For each particle in the universe—like electrons and protons—there exists a corresponding antiparticle with an opposite charge and identical mass, underpinning a fundamental aspect of the universe’s structure.
In 2000, mathematician and physicist Alexei Kitaev proposed that Majorana fermions can not only exist as elementary particles but also as quantum excitations within certain materials known as topological superconductors. These superconductors differ from conventional ones due to unique, stable quantum states located on their surfaces or edges, safeguarded by the material’s inherent topology, or the configuration of electron movement at the quantum level.
The surface states of topological superconductors contribute to their resilience against disruptions, which is why they are potentially valuable for creating more stable quantum computers. These specialized edge states operate like Majorana fermions, which are not found in regular superconductors. Theoretically, Majorana fermions could be harnessed to store quantum information in a non-local fashion, providing a means to protect qubits from decoherence.
Professor Seradjeh and his team investigated Majorana fermions in the specific context of superconductors that are “periodically driven,” meaning they are subjected to external energy sources that turn on and off in a steady rhythm. This periodic driving changes the characteristics of the Majorana fermions, resulting in the emergence of “Floquet Majorana fermions” (FMFs). These unique fermions exist in different states that are unattainable without the periodic drive and their behavior varies with the cycling energy source. Maintaining the FMFs and the unusual patterns they generate relies heavily on this periodic driving of the superconductor.
In normal conductors, electric current requires an applied voltage to flow between two points. However, a unique quantum tunneling process known as the “Josephson effect” enables current to pass between two superconductors without applied voltage. FMFs uniquely influence this Josephson current. In standard systems, the current flow between two superconductors repeats at consistent intervals. In contrast, FMFs display a current pattern that oscillates at half the typical rate, creating a distinctive signature that facilitates their detection.
Adjusting current with new methods
A significant finding from Seradjeh and his colleagues’ research is that the strength of the Josephson current—indicating how much electrical flow occurs—can be adjusted using a property known as the “chemical potential” of the superconductors. Essentially, the chemical potential serves as a dial for modifying the material’s characteristics, and the researchers found that by synchronizing it with the frequency of the external energy source, they could effect alterations. This discovery could provide scientists a new level of control over quantum materials and pave the way for advancements in quantum information processing, where manipulating quantum states with precision is crucial.
The realization that Floquet Majorana fermions possess unique, controllable properties could significantly contribute to the development of faster, error-resistant quantum computers. These insights supply researchers globally with a framework for detecting and investigating new properties in driven quantum systems.
