Quantum particles: Pulled and compressed

Date:
July 8, 2021
Source:
University of Innsbruck
Summary:
Only recently researchers have levitated and cooled nanoparticles
into the quantum regime. A research team now proposes a way to
harness the quantum properties of such particles before they lose
them due to decoherence. To this end, the wave function of the
particle is repeatedly expanded and compressed.



FULL STORY ==========================================================================
Only recently researchers have levitated and cooled nanoparticles into
the quantum regime. An Austrian research team led by Oriol Romero-Isart
now proposes a way to harness the quantum properties of such particles
before they lose them due to decoherence. To this end, the wave function
of the particle is repeatedly expanded and compressed in a loop.


==========================================================================
Very recently, researchers led by Markus Aspelmeyer at the University
of Vienna and Lukas Novotny at ETH Zurich cooled a glass nanoparticle
into the quantum regime for the first time. To do this, the particle is deprived of its kinetic energy with the help of lasers. What remains
are movements, so-called quantum fluctuations, which no longer follow
the laws of classical physics but those of quantum physics. The glass
sphere with which this has been achieved is significantly smaller than a
grain of sand, but still consists of several hundred million atoms. In
contrast to the microscopic world of photons and atoms, nanoparticles
provide an insight into the quantum nature of macroscopic objects. In collaboration with experimental physicist Markus Aspelmeyer, a team of theoretical physicists led by Oriol Romero-Isart of the University of
Innsbruck and the Institute of Quantum Optics and Quantum Information
of the Austrian Academy of Sciences is now proposing a way to harness
the quantum properties of nanoparticles for various applications.

Briefly delocalized "While atoms in the motional ground state bounce
around over distances larger than the size of the atom, the motion of macroscopic objects in the ground state is very, very small," explain
Talitha Weiss and Marc Roda-Llordes from the Innsbruck team. "The
quantum fluctuations of nanoparticles are smaller than the diameter of
an atom." To take advantage of the quantum nature of nanoparticles, the
wave function of the particles must be greatly expanded. In the Innsbruck quantum physicists' scheme, nanoparticles are trapped in optical fields
and cooled to the ground state. By rhythmically changing these fields, the particles now succeed in briefly delocalizing over exponentially larger distances. "Even the smallest perturbations may destroy the coherence
of the particles, which is why by changing the optical potentials,
we only briefly pull apart the wave function of the particles and then immediately compress it again," explains Oriol Romero-Isart. By repeatedly changing the potential, the quantum properties of the nanoparticle can
thus be harnessed.

Many applications With the new technique, the macroscopic quantum
properties can be studied in more detail. It also turns out that this
state is very sensitive to static forces. Thus, the method could enable
highly sensitive instruments that can be used to determine forces such
as gravity very precisely. Using two particles expanded and compressed simultaneously by this method, it would also be possible to entangle them
via a weak interaction and explore entirely new areas of the macroscopic quantum world.

Together with other proposals, the new concept forms the basis for the
ERC Synergy Grant project Q-Xtreme, which was granted last year. In this project, the research groups of Markus Aspelmeyer and Oriol Romero-Isart, together with Lukas Novotny and Romain Quidant of ETH Zurich, are pushing
one of the most fundamental principles of quantum physics to the extreme
limit by positioning a solid body of billions of atoms in two places at
the same time.

========================================================================== Story Source: Materials provided by University_of_Innsbruck. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. T. Weiss, M. Roda-Llordes, E. Torrontegui, M. Aspelmeyer, O. Romero-
Isart. Large Quantum Delocalization of a Levitated Nanoparticle
Using Optimal Control: Applications for Force Sensing and Entangling
via Weak Forces. Physical Review Letters, 2021; 127 (2) DOI:
10.1103/ PhysRevLett.127.023601 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/07/210707160507.htm

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