November 28, 2022


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Electrons, as a liquid, could help build perturbation-resistant quantum computers

Electrons, as a liquid, could help build perturbation-resistant quantum computers

A team of scientists from Nanyang Technology University (NTU) In Singapore, he studies peculiar phases of matter using scanning tunneling microscopy, which allows materials to be analyzed atom by atom. His team conducted experiments to show how a one-dimensional e-fluid could be controlled with unprecedented precision. Details are described in the magazine Nature Communications.

In ordinary materials, the repulsion of electrons is usually suppressed by the fact that they “avoid” each other. But in cases where the movement of electrons side by side in one direction is restricted, this freedom may be restricted. Each electron can only move while the others are moving.

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Due to interactions between electrons, at lower temperatures they can condense into a new liquid state, where they lose their individual identity and collectively behave as if they were completely different particles. This is called Tomonaga-Luttinger fluid, a rare phase of matter that physicists have tried to understand for more than half a century.

Unmatched liquid

Experimental studies of Tomonaga-Luttinger fluids are hampered by the fact that they only appear in a few specific places, such as carbon nanotubes. In addition, measuring their properties requires more sensitive experimental techniques compared to those used in the study of conventional materials.

a. NTU’s Bent Webber focused on the particular environment in which Tomonagi-Luttinger fluids can form, based on two-dimensional materials called QSH insulators. These materials are electrically isolated inside, allowing electrons to exist only at their one-dimensional boundaries, or “edges”.

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The electrons on this edge have a property that other Tomonaga-Luttinger fluids lack – they are “chiral” meaning that each electron’s spin (which describes its spin) is constrained in the direction in which it moves. This gives Tomonaga-Luttinger liquid unusual properties.

An important step towards better quantum computers – Prof. Ben Weber downtown / Photo. NTU

When the temperature drops to near absolute zero, the electrons in the Tomonaga-Luttinger spiral spontaneously assemble into units called “parafermions,” each made up of four electrons. Parapheromones can encode quantum information in a way that is perturbation-tolerant. Parafermion-based quantum techniques will literally have an ‘advantage’ over other methods by enabling error-resistant quantum computation.

a. Weber studied the one-dimensional boundaries of quantum insulators QSH under different conditions and described their properties using theoretical models. The strength of the interaction in a Luttinger fluid is determined by the so-called Luttinger parameter K, which determines whether or not electrons are sensitive to mutual repulsion. When K = 1, the electrons don’t interact at all. When K is less than 0.5, the interactions are strong and the electrons are forced to move collectively. This is the situation in which paraphermions are expected.

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K is strongly influenced by the choice of substrate, that is, the base material on which the system is grown. Moreover, the effects are stronger on certain types of edges. By varying these parameters, the team achieved K values ​​between 0.21 and 0.33. Such low K values ​​have not been previously observed in any Tomonag-Luttinger helical fluid.

The research conducted may represent an entirely new era in building quantum computers. Every now and then another “breakthrough” is reported, but this is one of those discoveries that could actually translate into applications for quantum computers.

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