Photon pairs are more sensitive to rotations than single photons

Date:
January 12, 2022
Source:
Tampere University
Summary:
Quantum states of light have enabled novel optical sensing schemes,
e.g., for measuring distance or position, with precisions impossible
to achieve with classical light sources such as lasers. The field
of quantum metrology has now been pushed even further as a team of
researchers showed that photons that are engineered to be entangled
in complex spatial structures have, due to quantum phenomena,
an advantage for sensing the smallest rotations. The new method
allows for more precise measurement than what could be achieved
by conventional means.



FULL STORY ==========================================================================
In the field of quantum metrology, scientists are developing novel
measurement schemes that benefit from quantum features and are more
precise and sensitive than classical conventional methods. The team
of researchers from Tampere University, Finland, and the National
Research Council of Canada has now shown how a simple and powerful
technique called two-photon N00N states can be used to create spatially structured quantum states of light that can go beyond the classical
limit in rotation estimation. The results are published in the journal
Physical Review Letters.


==========================================================================
"Our experimental results demonstrate a simple but powerful way of custom- tailoring two-photon quantum states and holds promise for applications
that can achieve high measurement precisions.The simplicity of our method
opens a path to creating a measurement system that beats the classical estimation limit with current technologies," explains Doctoral Researcher
and lead author Markus Hiekkama"ki.

Measurement precisions at the absolute quantum limit The method utilizes a fundamental quantum feature, i.e., the interference between two photons,
which is often termed photon bunching. In contrast to the more common
photon bunching into the same physical path, the novel scheme leads to
a bunching into the same spatial structure.

"In our case, the quantum interference results in an entangled state
of two photons. Because of the quantum nature of the realized state,
the entangled photon pair gives a better measurement precision when
compared to the same spatial shape imprinted on a similar amount of
single photons or laser light.

Using a counter-intuitive quantum response, we were able to show that
it will be possible to achieve measurement precisions at the absolute
quantum limit ," says Associate Professor Robert Fickler, leader of the Experimental Quantum Optics group at Tampere University.

Besides rotational measurements, the method allows the generation
of a large variety of different quantum states for transverse-spatial
modes. Hence, it could also be utilized in measurements of many different
types of systems as well as in fundamental tests of multi-photon quantum
states of light.

After demonstrating the advantage in rotational estimation, the
researchers are now planning on using the method to shed new light on
another fundamental property of waves called the Gouy phase. In addition,
they study how it could be extended into quantum-enhanced measurement
schemes in multiple degrees of freedom.

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


========================================================================== Journal Reference:
1. Markus Hiekkama"ki, Fre'de'ric Bouchard, Robert Fickler. Photonic
Angular
Superresolution Using Twisted N00N States. Physical Review Letters,
2021; 127 (26) DOI: 10.1103/PhysRevLett.127.263601 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/01/220112105642.htm
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