August 21, 2018
University of Queensland
How Einstein's equivalence
principle extends to the quantum world has been puzzling physicists for
decades, but a research team has now found the key to this question.
How Einstein's equivalence
principle extends to the quantum world has been puzzling physicists for
decades, but a team including a University of Queensland researcher has found
the key to this question.
UQ physicist, Dr Magdalena
Zych from the ARC Centre of Excellence for Engineered Quantum Systems, and the
University of Vienna's Professor Caslav Brukner have been working to discover
if quantum objects interact with gravity only through curved space-time.
"Einstein's equivalence
principle contends that the total inertial and gravitational mass of any
objects are equivalent, meaning all bodies fall in the same way when subject to
gravity," Dr Zych said.
"Physicists have been
debating whether the principle applies to quantum particles, so to translate it
to the quantum world we needed to find out how quantum particles interact with
gravity.
"We realised that to do
this we had to look at the mass."
Mass is dynamic quantity and
can have different values, and in quantum physics, mass of a particle can be in
a quantum 'superposition' of two different values.
In a state unique to quantum
physics, energy and mass can exist in a 'quantum superposition' -- as if they
consisted of two different values 'at the same time'.
"We realised that we had
to look how particles in such quantum states of the mass behave in order to
understand how a quantum particle sees gravity in general," she said.
"Our research found that
for quantum particles in quantum superpositions of different masses, the
principle implies additional restrictions that are not present for classical
particles -- this hadn't been discovered before.''
"It means that previous
studies that attempted to translate the principle to quantum physics were
incomplete because they focused on trajectories of the particles but neglected
the mass."
The study opens a door for new
experiments that are necessary to test if quantum particles obey the additional
restrictions that have been found.
Story Source:
Materials provided by University of Queensland. Note:
Content may be edited for style and length.
Journal Reference:
Magdalena Zych, Časlav
Brukner. Quantum formulation of the Einstein equivalence principle. Nature
Physics, 2018; DOI: 10.1038/s41567-018-0197-6
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