Tabletop quantum experiment could detect gravitational waves

Date:
July 1, 2020
Source:
University College London
Summary:
Tiny diamond crystals could be used as an incredibly sensitive and
small gravitational detector capable of measuring gravitational
waves, suggests new research.



FULL STORY ========================================================================== Predicted by Einstein's general theory of relativity, gravitational
waves are ripples in space-time generated by certain movements of
massive objects. They are important to study because they allow us to
detect events in the universe that would otherwise leave little or no observable light, like black hole collisions.


==========================================================================
In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO)
and the Virgo collaborations made the first direct observation of
gravitational waves.

The waves were emitted from a 1.3 billion-year-old collision between
two supermassive black holes and were detected using 4 km long optical interferometers as the event caused ripples in the Earth's space-time.

Researchers from UCL, University of Groningen, and University of Warwick propose a detector based on quantum technology that is 4000 times smaller
than the detectors currently in use and could detect mid-frequency gravitational waves.

The study, published today in New Journal of Physics, details how
state-of-the- art quantum technologies and experimental techniques can be
used to build a detector capable of measuring and comparing the strength
of gravity in two locations at the same time.

It would work by using nano-scale diamond crystals weighing ?10?^(-17)
kg. The crystals would be placed in a quantum spatial superposition
using Stern-Gerlach interferometry. Spatial superposition is a quantum
state where the crystals exist in two different places at the same time.

Quantum mechanics allows for an object, however big, to be
spatially delocalised in two different places at once. Despite being counter-intuitive and in direct conflict with our everyday experience,
the superposition principle of quantum mechanics has been experimentally verified using neutrons, electrons, ions and molecules.



========================================================================== Corresponding author Ryan Marshman (UCL Physics & Astronomy and UCLQ),
said: "Quantum gravitational sensors already exist using the superposition principle.

These sensors are used to measure Newtonian gravity and make for
incredibly accurate measurement devices. The quantum masses used by
current quantum gravitational sensors are much smaller such as atoms,
but experimental work is progressing the new interferometry techniques
needed to make our device work to study gravitational waves.

"We found that our detector could explore a different range of frequencies
of gravitational waves compared to LIGO. These frequencies might only
be available if scientists build large detectors in space with baselines
that are hundreds of thousands of kilometres in size." The team envision
that their proposed smaller detector could be used to build a network
of detectors that would be capable of picking out gravitational wave
signals from background noise. This network would also be potentially
useful giving precise information on the location of the objects that
are creating the gravitational waves.

Co-author, Professor Sougato Bose (UCL Physics & Astronomy and UCLQ),
said: "While the sensor we have proposed is ambitious in its scope,
there does not appear to be any fundamental or insurmountable obstacle
to its creation using current and near future technologies.

"All the technical elements to make this detector have been individually realised in different experiments around the world: the forces required,
the quality of the vacuum required, the method to place the crystals in superposition. The difficulty will come in putting it all together and
making sure the superposition stays intact." The next step is for the
team to collaborate with experimentalists to start building prototypes of
the device. Importantly, the same class of detectors can also contribute
to detecting whether gravity is a quantum force, as shown in recent work
at UCL and elsewhere.

Ryan Marshman said: "Indeed our initial ambition was to develop the device
to explore nonclassical gravity. But, since it would be a considerable
effort to realise such a device, we thought it was really important
to examine the efficacy of such a device also for measuring very weak
classical gravity such as gravitational waves and found out that it is promising!" The work was funded by the, Netherlands Organisation for Scientific Research, the Royal Society, and the Engineering and Physical Sciences Research council.


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


========================================================================== Journal Reference:
1. Ryan James Marshman, Anupam Mazumdar, Gavin Morley, Peter F Barker,
Steven Hoekstra, Sougato Bose. Mesoscopic Interference for Metric
and Curvature (MIMAC) & Gravitational Wave Detection. New Journal
of Physics, 2020; DOI: 10.1088/1367-2630/ab9f6c ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200701100006.htm

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