Nearly a century after Italian physicist Ettore Majorana laid the groundwork
for the discovery that electrons could be divided into halves, researchers
predict that split photons may also exist, according to a study from
Dartmouth and SUNY Polytechnic Institute researchers.
The finding that the building blocks of light can exist in a
previously-unimaginable split form advances the fundamental understanding of
light and how it behaves.
The theoretical discovery of the split photon—known as a "Majorana
boson"—was published in Physical Review Letters.
"This is a major paradigm change of how we understand light in a way that
was not believed to be possible," said Lorenza Viola, the James Frank Family
Professor of Physics at Dartmouth and senior researcher on the study. "Not
only did we find a new physical entity, but it was one that nobody believed
could exist."
Similar to how liquid water can change into ice or vapor under specific
conditions, the research indicates that light can also exist in a different
phase—one where photons appear as two distinct halves.
"Water is water regardless of its liquid or solid form. It just behaves
differently depending on physical conditions," said Viola. "This is how we
need to approach our understanding of light—like matter, it can exist in
different phases."
Rather than pieces that can be physically pulled apart, the photon halves
serve similar to the different sides of a coin. The two distinct parts make
up a whole, yet they can be described and function as separate units.
"Every photon can be thought of as the sum of two distinct halves," said
Vincent Flynn, a Ph.D. candidate at Dartmouth and first author of the paper.
"We were able to identify conditions for isolating these halves from one
another."
The research is based on the fundamentals of physics.
Particles come in two different types: fermions and bosons. Fermions, such
as electrons, tend to be solitary, avoiding each other at all costs. Bosons,
such as photons, tend to bunch together. Thus, it was natural for
researchers to assume that splitting bosons would be an insurmountable task.
The Dartmouth theory relies on energy-leaking, dissipating cavities that are
coupled together and filled with quantum packets of light. The research
predicts that particle halves appear at the edges of such a synthetic
platform: The Majorana boson was discovered.
"Our discovery provides the first hint that a previously unknown,
topological phase of light and matter which hosts Majorana bosons may
exist," said Flynn.
The theoretical finding builds on the prediction in 1937 of the existence of
neutral, electron-like particles known as Majorana fermions. In 2001,
researchers suggested a specific process for how electrons could actually be
halved in certain superconductors. But the photon had remained indivisible
until now.
According to the research team, Majorana bosons can be viewed as distant
relatives to Majorana fermions.
"Fermions and bosons are as different as two things can be in physics," said
Emilio Cobanera, assistant professor of physics at SUNY Polytechnic
Institute, and co-author of the study. "In effect, the particles are
distorted images of each other. The existence of the Majorana fermions was
our main clue that the Majorana boson was hiding somewhere in the funhouse
mirror."
Confirmation of the Majorana boson would still require a laboratory
experiment that observes the photon halves. Unlike the massive structures
built to detect the renowned Higgs boson, an experiment to detect photon
halves could be done on a tabletop. Such an experiment could utilize
existing or near-term technologies.
The team found that Majorana bosons are robust against experimental
imperfections and identifiable by distinct signatures. Although it is hard
to predict how the findings may be applied, those characteristics could
support the development of new types of quantum information processors,
optical sensors, and light amplifiers. The research also points the way
toward uncovering a new, exotic phase of matter and light.
"In order to make this discovery we had to challenge long-held beliefs and
really think outside the box," said Viola. "We have split something
previously thought to be unsplittable, and we'll never look at light the
same way."
Reference:
Vincent P. Flynn et al, Topology by Dissipation: Majorana Bosons in
Metastable Quadratic Markovian Dynamics, Physical Review Letters (2021).
DOI: 10.1103/PhysRevLett.127.245701
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Physics