• Sat. Dec 9th, 2023

    Critical Thought

    Critical thoughts on quantum technologies

    Understanding the Impact of Molecule Structure on Quantum Effects

    BySam Figg

    Nov 10, 2023
    Understanding the Impact of Molecule Structure on Quantum Effects

    Scientists have recently made a groundbreaking discovery regarding the influence of molecule chirality on electron spin. This mysterious phenomenon, known as “Chirality-Induced Spin Selectivity” (CISS), holds the potential to improve quantum computers and help unravel the biggest mystery of life’s origin. Deciphering the intricacies of CISS, which was first discovered approximately 25 years ago, has proven to be a formidable challenge for researchers. This quantum effect involves the alignment of electron spins based on the “handedness” of a molecule, implying a close connection between the macroscopic structure of a substance and its quantum mechanical properties. However, for the first time, experts have directly observed and measured this effect in molecules.

    A team led by Hannah J. Eckvahl from Northwestern University in Evanston successfully measured the exotic CISS effect by harnessing the properties of liquid crystals. They incorporated a chiral molecule, one that exists in two mirror-image versions, between two other molecular components through which an electron can flow. This resulting rod-shaped molecule aligns precisely in crystal-like structures. As a result, by applying a magnetic field, researchers were able to align the spins of electrons relative to the molecules, making the CISS effect observable.

    The CISS effect only allows electrons with a specific spin orientation to pass through a molecule with a given handedness. Conversely, the mirror-image version of the molecule permits only electrons with opposite spins to pass through. Eckvahl’s team directly measured this phenomenon in their sophisticated experiment, as reported in the journal “Science.” The researchers irradiated the molecule with laser light, exciting an electron in one part of the molecule. The electron then flowed through the chiral molecule in the middle to the other molecular component, but only when its spin aligned appropriately with the handedness of the molecule, determined by the magnetic field.

    Previously, the CISS effect had only been indirectly measured in molecules in contact with electrodes. This new experiment demonstrates that the tight interplay between the larger-scale structure of a molecule and the quantum properties of individual electrons is indeed a fundamental characteristic of chiral molecules. Consequently, such molecules can function as “spin rectifiers” and potentially play a role in future spin-based quantum computers.

    Furthermore, researchers speculate that CISS may hold the key to solving a central puzzle concerning the origin of life: why biomolecules almost always possess a specific handedness. Proteins, genetic molecules, and sugar building blocks each contain molecular components that exist in mirror-image forms, which living organisms do not utilize. The preference for a particular handedness was already established at the dawn of life, but the reasons behind this phenomenon and the selection of these molecules instead of their mirror images remain entirely mysterious. Some experts hypothesize that CISS may have played a significant role in the selection of these molecules during the origin of life.

    Frequently Asked Questions (FAQ)

    What is the CISS effect?

    The CISS effect, also known as “Chirality-Induced Spin Selectivity,” is a quantum phenomenon where the handedness of a molecule determines the alignment of electron spins flowing through it.

    How was the CISS effect measured?

    Scientists from Northwestern University used liquid crystals to create a chiral molecule, which they observed directly by aligning the spins of electrons with a magnetic field.

    What are chiral molecules?

    Chiral molecules possess a non-superimposable mirror image, similar to our hands. They can exist in left-handed and right-handed versions.

    How does the CISS effect impact quantum computers?

    Understanding the CISS effect can potentially enhance the performance of spin-based quantum computers, as chiral molecules can function as “spin rectifiers” in these systems.

    What is the significance of the CISS effect for the origin of life?

    The CISS effect may provide insights into the puzzle of why biomolecules have a specific handedness, a characteristic that was established at the origin of life. It is believed that CISS may have played a vital role in the selection of these molecules.